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Papers by Vaka Rögnvaldsdóttir

Research paper thumbnail of Sleep and physical activity characteristics in university students during the COVID-19 pandemic: A descriptive cross-sectional wrist actigraphy study

Sleep epidemiology, May 1, 2024

Research paper thumbnail of Longitudinal development and tracking of cardiorespiratory fitness from childhood to adolescence

Research paper thumbnail of Svefnlengd íslenskra grunnskólanema

Netla, Feb 8, 2022

Þrátt fyrir fjölda svefnrannsókna á undanförnum árum er enn margt á huldu um útbreiðslu svefnvenj... more Þrátt fyrir fjölda svefnrannsókna á undanförnum árum er enn margt á huldu um útbreiðslu svefnvenja meðal ungmenna. Naegur naetursvefn er mikilvaegur fyrir þroska, heilsu og námsgetu ungs fólks. Markmið rannsóknarinnar var að skoða hvort svefnlengd íslenskra skólanema samraemdist svefnráðleggingum, hver meðalsvefnlengd nemendanna vaeri og hver munur vaeri á tíðni ráðlagðs svefns og svefnlengd milli einstakra hópa nemenda. Landskönnunin "Heilsa og lífskjör skólanema" (HBSC) fór fram árið 2018 meðal nemenda í 6., 8. og 10. bekk. Alls svöruðu 7.159 nemendur á landinu öllu stöðluðum spurningalista. Nemendurnir voru meðal annars spurðir um háttatíma sinn og fótaferðartíma. Viðmið um naegilegan svefn voru borin saman við alþjóðlegar ráðleggingar ungmenna í 6. bekk (9-11 klst./nóttu), og fyrir nemendur í 8. og 10. bekk (8-10 klst./ nóttu). Niðurstöður sýndu að um 30% nemenda í 6., 8. og 10. bekk ná ekki viðmiðum um ráðlagða svefnlengd á virkum dögum. Piltar náðu síður ráðlagðri svefnlengd en stúlkur, og 10. bekkingar mun síður en nemendur í yngri bekkjardeildum. Nemendur sem áttu foreldra af erlendum uppruna sváfu skemur og náðu síður ráðlögðum svefni en aðrir nemendur. Nemendur sem bjuggu með báðum lífforeldrum sínum sváfu lengur og fengu oftar ráðlagðan svefn en nemendur í öðrum fjölskyldugerðum. Þá kom í ljós að nemendur á höfuðborgarsvaeðinu sváfu lengur og náðu frekar ráðlögðum svefni en nemendur af landsbyggðinni. Ekki var marktaekur munur á lengd naetursvefns eftir efnahag fjölskyldunnar. Umtalsverður hluti íslenskra ungmenna naer ekki naegum naetursvefni. Mikilvaegt er að gefa nánari gaum að naetursvefni íslenskra ungmenna, einkum meðal þeirra ungmenna sem fá hvað stystan naetursvefn.

Research paper thumbnail of Changes in health-related lifestyle choices of university students before and during the COVID-19 pandemic: Associations between food choices, physical activity and health

PLOS ONE, Jun 23, 2023

The COVID-19 pandemic has had a profound effect on our lives and society, influencing both indivi... more The COVID-19 pandemic has had a profound effect on our lives and society, influencing both individuals' lifestyles and habits. Recent research shows that anxiety and loneliness have continued to rise, along with changes in food and lifestyle choices. The aim of the study was to investigate whether the pandemic influenced food choices and consumption of energy drinks, alcohol, fruits, and vegetables among first-year university students. Additionally, assessing the relationship between mental and physical health, physical activity, and food choices. A total of 128 male and 128 female first-year students at the University of Iceland were invited to answer an electronic questionnaire in January and early February 2021. A total of 118 students (54% men) participated in the study and valid answers were 115 (46% participation rate). Almost half of the students (44%) experienced that their food choices had worsened, while 14% reported an improvement, compared to before the pandemic. Consumption of caffeinated beverages increased for 26% of students, while 19% experienced a decrease. Just over half of the students reported not drinking alcohol (13%) or reduced consumption (41%). Participants who reported that their mental health had deteriorated or remained the same tended to spend less time on physical activity and experienced worsened food choices (p<0.05). Similarly, those who spent less or the same time on physical activity estimated that their food choices had deteriorated (p<0.05). The COVID-19 pandemic has had a significant impact on the lifestyles of university students and this study has revealed how lifestyle choices and mental health seem to be highly affected by one another. Additionally, the potentially harmful effects of excessive intake of energy drinks need to be enhanced. Interestingly, about 40% of the respondents in the current study drank less alcohol during the pandemic than prior to the pandemic, indicating a strong relationship between alcohol drinking and social gatherings. This study reveals the importance of educating young people on healthy lifestyle choices and the importance of mental health needs to be emphasised.

Research paper thumbnail of 0260 Association Between Free-Living Physical Activity and Sleep in Icelandic Adolescents

Sleep, Apr 1, 2020

Introduction: In the current epidemic of opioid-related deaths, and widespread use of opioids to ... more Introduction: In the current epidemic of opioid-related deaths, and widespread use of opioids to treat chronic pain, there is a pressing need to understand the underlying risk factors that contribute to such devastating conditions. Shiftwork has been associated with adverse health outcomes. We tested whether shiftwork during middle age is linked to the development of chronic pain and opioid misuse. Methods: We studied 116,474 participants in active employment between 2006-2010 (mean age 57±8; range 37-71) from the UK Biobank, who have been followed for up to 10 years until 2017. We included participants who were free from all forms of selfreported pain, and were not taking opioid medications at baseline. Chronic pain and opioid use disorder diagnoses were determined using hospitalization records and diagnostic coding from ICD-10. Multivariate logistic regression models were performed to examine the associations of shiftwork status (yes/no) and nightshift frequency (none/occasional/permanent) and with incident chronic pain and/or opioid use disorder during follow-up. Models were adjusted for demographics, education, Townsend deprivation index, major confounders (BMI, diabetes, bone fractures/injuries, operations, peripheral vascular disease, joint/inflammatory diseases, cancer, standing/manual labor at work) and covariates (smoking, alcohol, high cholesterol, depression/anxiety, and cardiovascular diseases). Results: In total, 190 (1.6/1,000) developed chronic pain or opioid use disorders. Shiftworkers (n=17,673) saw a 1.5-fold increased risk (OR 1.56, 95% CI: 1.08-2.24, p=0.01) relative to day workers. Within shiftworkers, those who reported occasional nightshift work (n=3,966) were most vulnerable (OR 1.57, 95% CI: 1.06-2.34, p=0.02). Results remained similar after adjusting for baseline sleep duration, chronotype and insomnia. Conclusion: Shiftwork, and in particular rotating nightshift work is associated with increased risk for developing chronic pain and opioid use disorders. Replication is required to confirm the findings and to examine underlying mechanisms.

Research paper thumbnail of Hreyfing og svefn reykvískra ungmenna

Laeknabladid, Feb 5, 2018

eru taldir réttmaetir og áreiðanlegir við maelingar á hreyfingu og svefni hjá börnum og ungmennum... more eru taldir réttmaetir og áreiðanlegir við maelingar á hreyfingu og svefni hjá börnum og ungmennum. 14-17 Samanburður á hlutlaegum og huglaegum maelingum á svefnlengd unglinga bendir til þess að þaer huglaegu ofmeti svefnlengd, sem þýðir að ungmenni fá jafnvel enn styttri naetursvefn en hingað til hefur verið talið. 18 Fáar rannsóknir hafa metið tengsl hreyfingar og svefns með hlutlaegum maelingum á báðum breytum. 10 Markmið rannsóknarinnar var að meta: a) hversu hátt hlutfall 16 ára reykvískra ungmenna uppfyllir viðmið um hreyfingu og svefn, b) hvort tengsl séu á milli magns hreyfingar og svefns og ennfremur c) kynjamun á hreyfingu og svefni. Efniviður og aðferðir Rannsóknarsnið og val á þátttakendum Rannsóknin er þversniðsrannsókn byggð á gögnum sem safnað var á tímabilinu apríl-júní 2015. Þátttakendur voru nemendur 10. bekkjar við 6 grunnskóla í Reykjavík, langflestir faeddir árið 1999. Alls var 411 nemendum boðin þátttaka og 315 þáðu boðið (76,6% þátttökuhlutfall). Maelingar fóru fram í hverjum skóla fyrir sig. Ungmennin og foreldrar/forráðamenn þeirra undirrituðu upplýst samþykki áður en þátttaka hófst. Vísindasiðanefnd samþykkti framkvaemd rannsóknarinnar (VSN b200605002&03).

Research paper thumbnail of Longitudinal Change in Adolescent Bedtimes Measured by Self-Report and Actigraphy

Journal for the measurement of physical behaviour, Dec 1, 2019

Introduction: Sleep is often quantified using self-report or actigraphy. Self-report is practical... more Introduction: Sleep is often quantified using self-report or actigraphy. Self-report is practical and less technically challenging, but prone to bias. We sought to determine whether these methods have comparable sensitivity to measure longitudinal changes in adolescent bedtimes. Methods: We measured one week of free-living sleep with wrist actigraphy and usual bedtime on school nights and non-school nights with self-report questionnaire in 144 students at 15 y and 17 y. Results: Self-reported and actigraphy-measured bedtimes were correlated with one another at 15 y and 17 y (p < .001), but reported bedtime was consistently earlier (>30 minutes, p < .001) and with wide inter-method confidence intervals (> ±106 minutes). Mean inter-method discrepancy did not differ on school nights at 15 y and 17 y but was greater at 17 y on non-school nights (p = .002). Inter-method discrepancy at 15 y was not correlated to that at 17 y. Mean change in self-reported school night bedtime from 15 y to 17 y did not differ from that by actigraphy, but selfreported bedtime changed less on non-school nights (p = .002). Two-year changes in self-reported bedtime did not correlate with changes measured by actigraphy. Conclusions: Although methods were correlated, consistently earlier self-reported bedtime suggests report-bias. More varied non-school night bedtimes challenge the accuracy of self-report and actigraphy, reducing sensitivity to change. On school nights, the methods did not differ in group-level sensitivity to changes in bedtime. However, lack of correlation between bedtime changes by each method suggests sensitivity to individual-level change was different. Methodological differences in sensitivity to individual-and group-level change should be considered in longitudinal studies of adolescent sleep patterns.

Research paper thumbnail of Sleep deficiency on school days in Icelandic youth, as assessed by wrist accelerometry

Sleep Medicine, May 1, 2017

Aims: The purpose of this study was to objectively measure, with wrist-worn actigraphy, freelivin... more Aims: The purpose of this study was to objectively measure, with wrist-worn actigraphy, freeliving sleeping patterns in Icelandic adolescents, and to compare sleep duration, sleep quality and clock times between school days (SchD) and non-school days (NSchD) and the association between sleep and body mass index (BMI). Methods: A cross-sectional study on 15.9-year-old (±0.3) adolescents from six schools in Reykjavík, Iceland, took place in the spring of 2015. Free-living sleep was measured on 301 subjects (122 boys and 179 girls) over seven days using wrist-worn actigraphy accelerometers. Total rest time (TRT), total sleep time (TST), sleep quality markers, and clock times for sleep were quantified and compared between SchD and NSchD and between the sexes, using paired and group t-tests as appropriate. Linear regression was used to assess the association between sleep parameters and BMI. Results: On SchD, TST was 6.2 ± 0.7 h, with sleep efficiency (SLE) of 87.9 ± 4.4% for the group. On NSchD, TST increased to 7.3 ± 1.1 h (p < 0.001), although SLE decreased to 87.4 ± 4.7% (p < 0.05). On SchD and NSchD, 67% and 93% had bed times after midnight, respectively, and on SchD 10.7% met sleep recommendations (8 h/night). There was no association between BMI and average sleep parameters. Conclusion: The majority of Icelandic adolescents did not get the recommended number of hours of sleep, especially on SchD. While TST increased on NSchD, many participants still did not achieve the recommendations. These findings provide information on the sleep patterns of adolescents and may serve as reference for development of policies and interventions to promote better sleep practices.

Research paper thumbnail of Hreyfing íslenskra grunnskólanema

Netla, Feb 8, 2022

Gildi hreyfingar fyrir líkamlega og andlega heilsu er vel þekkt. Þrátt fyrir þá vitneskju dregur ... more Gildi hreyfingar fyrir líkamlega og andlega heilsu er vel þekkt. Þrátt fyrir þá vitneskju dregur úr hreyfingu frá barnsaldri til unglingsára og almennt er hreyfingu ábótavant. Því er mikilvaegt að kanna hreyfingu barna og unglinga með það fyrir augum að efla hana og sporna við hreyfingarleysi. Markmið þessarar rannsóknar var að kanna umfang líkamlegrar hreyfingar íslenskra grunnskólanema í 6., 8. og 10. bekk og tengsl hennar við kyn, aldur, uppruna, fjölskyldugerð, efnahag og búsetu. Sérstaklega var athugað hve hátt hlutfall nemendanna naeði ráðlagðri 60 mínútna hreyfingu daglega. Unnið var úr gögnum úr landskönnuninni Heilsa og lífskjör skólanema (Health Behavior in School-aged Children-HBSC) sem fór fram árið 2018. Alls tóku 6.102 nemendur í 6., 8. og 10. bekk úr 86 grunnskólum á landinu þátt í rannsókninni. Spurningalistar voru lagðir fyrir nemendur og meðal annars var spurt um fjölda daga á viku sem þátttakendur stunduðu "líkamlega hreyfingu samanlagt í 60 mínútur eða meira á dag". Þá var einnig spurt um kyn og bekkjardeild, efnahagslega stöðu fjölskyldu, uppruna foreldra, fjölskyldugerð og búsetu. Að meðaltali stundaði nemendahópurinn líkamlega hreyfingu í 4,5 daga í viku. Einungis 21% nemenda náði viðmiði um ráðlagða daglega hreyfingu. Fleiri piltar en stúlkur náðu viðmiðum um hreyfingu og fleiri nemendur í 6. bekk samanborið við eldri nemendur. Nemendur sem tilheyrðu fjölskyldum með lakari efnahag, bjuggu ekki með báðum kynforeldrum, eða áttu foreldra af erlendum uppruna, náðu síður viðmiðum um ráðlagða hreyfingu. Ekki var munur á hreyfingu grunnskólanema eftir búsetu þeirra. Vinna þarf að hreyfieflingu grunnskólanema með fraeðslu um gildi hennar, daglegum hreyfistundum á skólatíma og markvissum íþróttatímum. Jafna þarf þátttöku barna í íþróttum utan skólans með aðkomu sveitarfélaganna. Fjölga þarf möguleikum til hreyfingar fyrir alla utan húss og innan í sveitarfélögum landsins.

Research paper thumbnail of Body composition and dietary intake of energy giving nutrients among older age groups

Research paper thumbnail of Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents

Journal of Sleep Research, Jun 14, 2021

Sleep has been shown to affect cognitive function in laboratory studies; however, its association... more Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self‐reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free‐living sleep quantity, quality, and timing of 15‐year‐old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement. We measured sleep with wrist actiography for 1 week in 253 (150 girls) Icelandic adolescents with a mean (SD) age of 15.9 (0.3) years. Multiple linear regression was used to assess associations between sleep parameters and combined standardised examination scores in mathematics, English, and Icelandic obtained from the Icelandic Directorate of Education. We found that students went to bed at 00:49 hours (± 51.8 min) and slept for a mean (SD) of 6.6 (0.7) hr/night, with a median (interquartile range) night‐to‐night variation in sleep duration of 1.2 (0.7) hr and an efficiency of 88.1 (5.3)%. Combined analyses adjusted for sex, demonstrated that both bedtime and night‐to‐night variability in total sleep time were negatively associated with the average score across all topics. Sex‐specific associations did not indicate clear differences between boys and girls. These findings suggest that, in addition to appropriate sleep duration, public health guidance should also highlight the importance of early and consistent sleep schedules to academic achievement for both boys and girls.

Research paper thumbnail of Less physical activity and more varied and disrupted sleep is associated with a less favorable metabolic profile in adolescents

Background Sleep and physical activity are modifiable behaviors that play an important role in pr... more Background Sleep and physical activity are modifiable behaviors that play an important role in preventing overweight, obesity, and metabolic health problems. Studies of the association between concurrent objective measures of sleep, physical activity, and metabolic risk factors among adolescents are limited. Objective The aim of the study was to examine the association between metabolic risk factors and objectively measured school day physical activity and sleep duration, quality, onset, and variability in adolescents. Materials and Methods We measured one school week of free-living sleep and physical activity with wrist actigraphy in 252 adolescents (146 girls), aged 15.8±0.3 years. Metabolic risk factors included body mass index, waist circumference, total body and trunk fat percentage, resting blood pressure, and fasting glucose and insulin levels. Multiple linear regression adjusted for sex, parental education, and day length was used to assess associations between metabolic risk factors and sleep and activity parameters. Results On average, participants went to bed at 00:22±0.88 hours and slept 6.2±0.7 hours/night, with 0.83±0.36 hours of awakenings/night. However, night-tonight variability in sleep duration (0.87±0.57 hours) and bedtime (0.79±0.58 hours) was considerable. Neither average sleep duration nor mean bedtime was associated with any metabolic risk factors. However, greater night-tonight variability in sleep duration was associated with higher total body (β=1.9±0.9 .

Research paper thumbnail of Changes in sleep and activity from age 15 to 17 in students with traditional and college-style school schedules

Sleep Health, Dec 1, 2020

Objectives:Sleep duration and physical activity decline with age during adolescence. Earlier scho... more Objectives:Sleep duration and physical activity decline with age during adolescence. Earlier school schedules may contribute to these declines. The aim of this longitudinal study was to track changes in sleep and activity of Icelandic youth from primary to secondary school and compare students who enrolled in secondary schools with traditional and college-style schedules.Methods:We measured free-living sleep and activity with wrist actigraphy and body composition by dual-energy x-ray absorptiometry in 145 students at age 15 and age 17, when 58% attended schools with college-style scheduling. Differences from 15 to 17 and between students of different school structures were assessed with mixed-effect models.Results:Actigraphs were worn for 7.1±0.4 nights at 15 and 6.9±0.4 nights at 17. Overall, sleep duration decreased from 6.6±0.7 h/night to 6.2±0.7 h/night from age 15 to 17 (p<0.001). Students with traditional schedules reduced school-night sleep duration 26 min/night at follow-up (p<0.001), while sleep duration did not change for college-style students. All students went to bed later on school nights at follow-up, but only college-style students rose later. Sleep efficiency and awakenings did not differ by schedule-type. Neither sex changed body fat percentage, but average school-day activity decreased by 19% (p<0.001) on follow-up and did not differ by schedule-type.Conclusions:Over the two-year period, adolescents decreased weekly sleep duration and activity, but only those continuing traditional schedules reduced school-night sleep. This suggests greater individual control of school schedule may preserve sleep duration in this age group, which may be beneficial during the transition into adulthood.

Research paper thumbnail of Less screen time and more physical activity is associated with more stable sleep patterns among Icelandic adolescents

Sleep Health, Oct 1, 2020

Objectives: Emerging evidence suggests that inconsistent sleep may affect physical and psychologi... more Objectives: Emerging evidence suggests that inconsistent sleep may affect physical and psychological health. Thus, it is important to identify modifiable determinants of sleep variability. Screen time and physical activity are both thought to affect sleep, but studies of their relationship to sleep variability using objective measures are lacking. We examined cross-sectional associations between these variables in mid-teen adolescents using objectively measured sleep and activity. Methods: Wrist-worn accelerometers were used to measure one week of sleep and activity in 315 tenth grade students (mean age 15.8y) from six Reykjavik compulsory schools. Participants reported their daily hours of screen time. Regression analysis was used to explore associations of screen time and physical activity with variability in duration, quality, and timing of sleep, adjusting for DXA-measured body fat percentage, parental education, and physical activity or screen time.

Research paper thumbnail of 0105 Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents

Sleep, May 25, 2022

and Digestive and Kidney Diseases 2 0Introduction: Sleep has been shown to affect cognitive funct... more and Digestive and Kidney Diseases 2 0Introduction: Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self-reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free-living sleep quantity, quality, and timing of 15-year-old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement. Methods: We measured sleep with wrist actiography for 1 week in 253 (150 girls) Icelandic adolescents with a mean (SD) age of 15.9 (0.3) years. Multiple linear regression was used to assess associations between sleep parameters and combined standardised examination scores in mathematics, English, and Icelandic obtained from the Icelandic Directorate of Education. Results: We found that students went to bed at 00:49 hours (± 51.8 min) and slept for a mean (SD) of 6.6 (0.7) hr/night, with a median (interquartile range) night-tonight variation in sleep duration of 1.2 (0.7) hr and an efficiency of 88.1 (5.3)%. Combined analyses adjusted for sex, demonstrated that both bedtime and night-tonight variability in total sleep time were negatively associated with the average score across all topics. Sex-specific associations did not indicate clear differences between boys and girls. Conclusion: These findings suggest that, in addition to appropriate sleep duration, public health guidance should also highlight the importance of early and consistent sleep schedules to academic achievement for both boys and girls.

Research paper thumbnail of Sleeping Behavior and Physical Health of Icelandic Adolescents

Research paper thumbnail of Screen Time and Body Image in Icelandic Adolescents: Sex-Specific Cross-Sectional and Longitudinal Associations

International Journal of Environmental Research and Public Health, Jan 24, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Organized Sport Participation, Physical Activity, Sleep and Screen Time in 16-Year-Old Adolescents

International Journal of Environmental Research and Public Health, Mar 18, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Svefn, hreyfing og heilsa íslenskra ungmenna

Background Sleep and physical activity are essential functions of human health. According to Inte... more Background Sleep and physical activity are essential functions of human health. According to International recommendations, adolescents should sleep 8-10 hours each night and engage in moderate to vigorous physical activity for at least 60 minutes per day for overall wellbeing. Previous studies have shown that during adolescence, sleep patterns change and most sleep studies up to date are based on subjective data for sleep duration and quality. Technological advancement in measurement of sleep and physical activity with objective measures adds value to the literature. Aim The main aim of the dissertation was to measure free-living sleep and physical activity in Icelandic youth at baseline (15 years) and two years later (17 years), and explore associations between sleep (duration, quality and timing), physical activity, and body composition. In addition, to compare sensitivity and agreement between subjective and objective measurements of sleep among and between ages of 15 and 17 yea...

Research paper thumbnail of Henta lágkolvetnamataræði og föstur í þjálfun?

Research paper thumbnail of Sleep and physical activity characteristics in university students during the COVID-19 pandemic: A descriptive cross-sectional wrist actigraphy study

Sleep epidemiology, May 1, 2024

Research paper thumbnail of Longitudinal development and tracking of cardiorespiratory fitness from childhood to adolescence

Research paper thumbnail of Svefnlengd íslenskra grunnskólanema

Netla, Feb 8, 2022

Þrátt fyrir fjölda svefnrannsókna á undanförnum árum er enn margt á huldu um útbreiðslu svefnvenj... more Þrátt fyrir fjölda svefnrannsókna á undanförnum árum er enn margt á huldu um útbreiðslu svefnvenja meðal ungmenna. Naegur naetursvefn er mikilvaegur fyrir þroska, heilsu og námsgetu ungs fólks. Markmið rannsóknarinnar var að skoða hvort svefnlengd íslenskra skólanema samraemdist svefnráðleggingum, hver meðalsvefnlengd nemendanna vaeri og hver munur vaeri á tíðni ráðlagðs svefns og svefnlengd milli einstakra hópa nemenda. Landskönnunin "Heilsa og lífskjör skólanema" (HBSC) fór fram árið 2018 meðal nemenda í 6., 8. og 10. bekk. Alls svöruðu 7.159 nemendur á landinu öllu stöðluðum spurningalista. Nemendurnir voru meðal annars spurðir um háttatíma sinn og fótaferðartíma. Viðmið um naegilegan svefn voru borin saman við alþjóðlegar ráðleggingar ungmenna í 6. bekk (9-11 klst./nóttu), og fyrir nemendur í 8. og 10. bekk (8-10 klst./ nóttu). Niðurstöður sýndu að um 30% nemenda í 6., 8. og 10. bekk ná ekki viðmiðum um ráðlagða svefnlengd á virkum dögum. Piltar náðu síður ráðlagðri svefnlengd en stúlkur, og 10. bekkingar mun síður en nemendur í yngri bekkjardeildum. Nemendur sem áttu foreldra af erlendum uppruna sváfu skemur og náðu síður ráðlögðum svefni en aðrir nemendur. Nemendur sem bjuggu með báðum lífforeldrum sínum sváfu lengur og fengu oftar ráðlagðan svefn en nemendur í öðrum fjölskyldugerðum. Þá kom í ljós að nemendur á höfuðborgarsvaeðinu sváfu lengur og náðu frekar ráðlögðum svefni en nemendur af landsbyggðinni. Ekki var marktaekur munur á lengd naetursvefns eftir efnahag fjölskyldunnar. Umtalsverður hluti íslenskra ungmenna naer ekki naegum naetursvefni. Mikilvaegt er að gefa nánari gaum að naetursvefni íslenskra ungmenna, einkum meðal þeirra ungmenna sem fá hvað stystan naetursvefn.

Research paper thumbnail of Changes in health-related lifestyle choices of university students before and during the COVID-19 pandemic: Associations between food choices, physical activity and health

PLOS ONE, Jun 23, 2023

The COVID-19 pandemic has had a profound effect on our lives and society, influencing both indivi... more The COVID-19 pandemic has had a profound effect on our lives and society, influencing both individuals' lifestyles and habits. Recent research shows that anxiety and loneliness have continued to rise, along with changes in food and lifestyle choices. The aim of the study was to investigate whether the pandemic influenced food choices and consumption of energy drinks, alcohol, fruits, and vegetables among first-year university students. Additionally, assessing the relationship between mental and physical health, physical activity, and food choices. A total of 128 male and 128 female first-year students at the University of Iceland were invited to answer an electronic questionnaire in January and early February 2021. A total of 118 students (54% men) participated in the study and valid answers were 115 (46% participation rate). Almost half of the students (44%) experienced that their food choices had worsened, while 14% reported an improvement, compared to before the pandemic. Consumption of caffeinated beverages increased for 26% of students, while 19% experienced a decrease. Just over half of the students reported not drinking alcohol (13%) or reduced consumption (41%). Participants who reported that their mental health had deteriorated or remained the same tended to spend less time on physical activity and experienced worsened food choices (p<0.05). Similarly, those who spent less or the same time on physical activity estimated that their food choices had deteriorated (p<0.05). The COVID-19 pandemic has had a significant impact on the lifestyles of university students and this study has revealed how lifestyle choices and mental health seem to be highly affected by one another. Additionally, the potentially harmful effects of excessive intake of energy drinks need to be enhanced. Interestingly, about 40% of the respondents in the current study drank less alcohol during the pandemic than prior to the pandemic, indicating a strong relationship between alcohol drinking and social gatherings. This study reveals the importance of educating young people on healthy lifestyle choices and the importance of mental health needs to be emphasised.

Research paper thumbnail of 0260 Association Between Free-Living Physical Activity and Sleep in Icelandic Adolescents

Sleep, Apr 1, 2020

Introduction: In the current epidemic of opioid-related deaths, and widespread use of opioids to ... more Introduction: In the current epidemic of opioid-related deaths, and widespread use of opioids to treat chronic pain, there is a pressing need to understand the underlying risk factors that contribute to such devastating conditions. Shiftwork has been associated with adverse health outcomes. We tested whether shiftwork during middle age is linked to the development of chronic pain and opioid misuse. Methods: We studied 116,474 participants in active employment between 2006-2010 (mean age 57±8; range 37-71) from the UK Biobank, who have been followed for up to 10 years until 2017. We included participants who were free from all forms of selfreported pain, and were not taking opioid medications at baseline. Chronic pain and opioid use disorder diagnoses were determined using hospitalization records and diagnostic coding from ICD-10. Multivariate logistic regression models were performed to examine the associations of shiftwork status (yes/no) and nightshift frequency (none/occasional/permanent) and with incident chronic pain and/or opioid use disorder during follow-up. Models were adjusted for demographics, education, Townsend deprivation index, major confounders (BMI, diabetes, bone fractures/injuries, operations, peripheral vascular disease, joint/inflammatory diseases, cancer, standing/manual labor at work) and covariates (smoking, alcohol, high cholesterol, depression/anxiety, and cardiovascular diseases). Results: In total, 190 (1.6/1,000) developed chronic pain or opioid use disorders. Shiftworkers (n=17,673) saw a 1.5-fold increased risk (OR 1.56, 95% CI: 1.08-2.24, p=0.01) relative to day workers. Within shiftworkers, those who reported occasional nightshift work (n=3,966) were most vulnerable (OR 1.57, 95% CI: 1.06-2.34, p=0.02). Results remained similar after adjusting for baseline sleep duration, chronotype and insomnia. Conclusion: Shiftwork, and in particular rotating nightshift work is associated with increased risk for developing chronic pain and opioid use disorders. Replication is required to confirm the findings and to examine underlying mechanisms.

Research paper thumbnail of Hreyfing og svefn reykvískra ungmenna

Laeknabladid, Feb 5, 2018

eru taldir réttmaetir og áreiðanlegir við maelingar á hreyfingu og svefni hjá börnum og ungmennum... more eru taldir réttmaetir og áreiðanlegir við maelingar á hreyfingu og svefni hjá börnum og ungmennum. 14-17 Samanburður á hlutlaegum og huglaegum maelingum á svefnlengd unglinga bendir til þess að þaer huglaegu ofmeti svefnlengd, sem þýðir að ungmenni fá jafnvel enn styttri naetursvefn en hingað til hefur verið talið. 18 Fáar rannsóknir hafa metið tengsl hreyfingar og svefns með hlutlaegum maelingum á báðum breytum. 10 Markmið rannsóknarinnar var að meta: a) hversu hátt hlutfall 16 ára reykvískra ungmenna uppfyllir viðmið um hreyfingu og svefn, b) hvort tengsl séu á milli magns hreyfingar og svefns og ennfremur c) kynjamun á hreyfingu og svefni. Efniviður og aðferðir Rannsóknarsnið og val á þátttakendum Rannsóknin er þversniðsrannsókn byggð á gögnum sem safnað var á tímabilinu apríl-júní 2015. Þátttakendur voru nemendur 10. bekkjar við 6 grunnskóla í Reykjavík, langflestir faeddir árið 1999. Alls var 411 nemendum boðin þátttaka og 315 þáðu boðið (76,6% þátttökuhlutfall). Maelingar fóru fram í hverjum skóla fyrir sig. Ungmennin og foreldrar/forráðamenn þeirra undirrituðu upplýst samþykki áður en þátttaka hófst. Vísindasiðanefnd samþykkti framkvaemd rannsóknarinnar (VSN b200605002&03).

Research paper thumbnail of Longitudinal Change in Adolescent Bedtimes Measured by Self-Report and Actigraphy

Journal for the measurement of physical behaviour, Dec 1, 2019

Introduction: Sleep is often quantified using self-report or actigraphy. Self-report is practical... more Introduction: Sleep is often quantified using self-report or actigraphy. Self-report is practical and less technically challenging, but prone to bias. We sought to determine whether these methods have comparable sensitivity to measure longitudinal changes in adolescent bedtimes. Methods: We measured one week of free-living sleep with wrist actigraphy and usual bedtime on school nights and non-school nights with self-report questionnaire in 144 students at 15 y and 17 y. Results: Self-reported and actigraphy-measured bedtimes were correlated with one another at 15 y and 17 y (p < .001), but reported bedtime was consistently earlier (>30 minutes, p < .001) and with wide inter-method confidence intervals (> ±106 minutes). Mean inter-method discrepancy did not differ on school nights at 15 y and 17 y but was greater at 17 y on non-school nights (p = .002). Inter-method discrepancy at 15 y was not correlated to that at 17 y. Mean change in self-reported school night bedtime from 15 y to 17 y did not differ from that by actigraphy, but selfreported bedtime changed less on non-school nights (p = .002). Two-year changes in self-reported bedtime did not correlate with changes measured by actigraphy. Conclusions: Although methods were correlated, consistently earlier self-reported bedtime suggests report-bias. More varied non-school night bedtimes challenge the accuracy of self-report and actigraphy, reducing sensitivity to change. On school nights, the methods did not differ in group-level sensitivity to changes in bedtime. However, lack of correlation between bedtime changes by each method suggests sensitivity to individual-level change was different. Methodological differences in sensitivity to individual-and group-level change should be considered in longitudinal studies of adolescent sleep patterns.

Research paper thumbnail of Sleep deficiency on school days in Icelandic youth, as assessed by wrist accelerometry

Sleep Medicine, May 1, 2017

Aims: The purpose of this study was to objectively measure, with wrist-worn actigraphy, freelivin... more Aims: The purpose of this study was to objectively measure, with wrist-worn actigraphy, freeliving sleeping patterns in Icelandic adolescents, and to compare sleep duration, sleep quality and clock times between school days (SchD) and non-school days (NSchD) and the association between sleep and body mass index (BMI). Methods: A cross-sectional study on 15.9-year-old (±0.3) adolescents from six schools in Reykjavík, Iceland, took place in the spring of 2015. Free-living sleep was measured on 301 subjects (122 boys and 179 girls) over seven days using wrist-worn actigraphy accelerometers. Total rest time (TRT), total sleep time (TST), sleep quality markers, and clock times for sleep were quantified and compared between SchD and NSchD and between the sexes, using paired and group t-tests as appropriate. Linear regression was used to assess the association between sleep parameters and BMI. Results: On SchD, TST was 6.2 ± 0.7 h, with sleep efficiency (SLE) of 87.9 ± 4.4% for the group. On NSchD, TST increased to 7.3 ± 1.1 h (p < 0.001), although SLE decreased to 87.4 ± 4.7% (p < 0.05). On SchD and NSchD, 67% and 93% had bed times after midnight, respectively, and on SchD 10.7% met sleep recommendations (8 h/night). There was no association between BMI and average sleep parameters. Conclusion: The majority of Icelandic adolescents did not get the recommended number of hours of sleep, especially on SchD. While TST increased on NSchD, many participants still did not achieve the recommendations. These findings provide information on the sleep patterns of adolescents and may serve as reference for development of policies and interventions to promote better sleep practices.

Research paper thumbnail of Hreyfing íslenskra grunnskólanema

Netla, Feb 8, 2022

Gildi hreyfingar fyrir líkamlega og andlega heilsu er vel þekkt. Þrátt fyrir þá vitneskju dregur ... more Gildi hreyfingar fyrir líkamlega og andlega heilsu er vel þekkt. Þrátt fyrir þá vitneskju dregur úr hreyfingu frá barnsaldri til unglingsára og almennt er hreyfingu ábótavant. Því er mikilvaegt að kanna hreyfingu barna og unglinga með það fyrir augum að efla hana og sporna við hreyfingarleysi. Markmið þessarar rannsóknar var að kanna umfang líkamlegrar hreyfingar íslenskra grunnskólanema í 6., 8. og 10. bekk og tengsl hennar við kyn, aldur, uppruna, fjölskyldugerð, efnahag og búsetu. Sérstaklega var athugað hve hátt hlutfall nemendanna naeði ráðlagðri 60 mínútna hreyfingu daglega. Unnið var úr gögnum úr landskönnuninni Heilsa og lífskjör skólanema (Health Behavior in School-aged Children-HBSC) sem fór fram árið 2018. Alls tóku 6.102 nemendur í 6., 8. og 10. bekk úr 86 grunnskólum á landinu þátt í rannsókninni. Spurningalistar voru lagðir fyrir nemendur og meðal annars var spurt um fjölda daga á viku sem þátttakendur stunduðu "líkamlega hreyfingu samanlagt í 60 mínútur eða meira á dag". Þá var einnig spurt um kyn og bekkjardeild, efnahagslega stöðu fjölskyldu, uppruna foreldra, fjölskyldugerð og búsetu. Að meðaltali stundaði nemendahópurinn líkamlega hreyfingu í 4,5 daga í viku. Einungis 21% nemenda náði viðmiði um ráðlagða daglega hreyfingu. Fleiri piltar en stúlkur náðu viðmiðum um hreyfingu og fleiri nemendur í 6. bekk samanborið við eldri nemendur. Nemendur sem tilheyrðu fjölskyldum með lakari efnahag, bjuggu ekki með báðum kynforeldrum, eða áttu foreldra af erlendum uppruna, náðu síður viðmiðum um ráðlagða hreyfingu. Ekki var munur á hreyfingu grunnskólanema eftir búsetu þeirra. Vinna þarf að hreyfieflingu grunnskólanema með fraeðslu um gildi hennar, daglegum hreyfistundum á skólatíma og markvissum íþróttatímum. Jafna þarf þátttöku barna í íþróttum utan skólans með aðkomu sveitarfélaganna. Fjölga þarf möguleikum til hreyfingar fyrir alla utan húss og innan í sveitarfélögum landsins.

Research paper thumbnail of Body composition and dietary intake of energy giving nutrients among older age groups

Research paper thumbnail of Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents

Journal of Sleep Research, Jun 14, 2021

Sleep has been shown to affect cognitive function in laboratory studies; however, its association... more Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self‐reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free‐living sleep quantity, quality, and timing of 15‐year‐old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement. We measured sleep with wrist actiography for 1 week in 253 (150 girls) Icelandic adolescents with a mean (SD) age of 15.9 (0.3) years. Multiple linear regression was used to assess associations between sleep parameters and combined standardised examination scores in mathematics, English, and Icelandic obtained from the Icelandic Directorate of Education. We found that students went to bed at 00:49 hours (± 51.8 min) and slept for a mean (SD) of 6.6 (0.7) hr/night, with a median (interquartile range) night‐to‐night variation in sleep duration of 1.2 (0.7) hr and an efficiency of 88.1 (5.3)%. Combined analyses adjusted for sex, demonstrated that both bedtime and night‐to‐night variability in total sleep time were negatively associated with the average score across all topics. Sex‐specific associations did not indicate clear differences between boys and girls. These findings suggest that, in addition to appropriate sleep duration, public health guidance should also highlight the importance of early and consistent sleep schedules to academic achievement for both boys and girls.

Research paper thumbnail of Less physical activity and more varied and disrupted sleep is associated with a less favorable metabolic profile in adolescents

Background Sleep and physical activity are modifiable behaviors that play an important role in pr... more Background Sleep and physical activity are modifiable behaviors that play an important role in preventing overweight, obesity, and metabolic health problems. Studies of the association between concurrent objective measures of sleep, physical activity, and metabolic risk factors among adolescents are limited. Objective The aim of the study was to examine the association between metabolic risk factors and objectively measured school day physical activity and sleep duration, quality, onset, and variability in adolescents. Materials and Methods We measured one school week of free-living sleep and physical activity with wrist actigraphy in 252 adolescents (146 girls), aged 15.8±0.3 years. Metabolic risk factors included body mass index, waist circumference, total body and trunk fat percentage, resting blood pressure, and fasting glucose and insulin levels. Multiple linear regression adjusted for sex, parental education, and day length was used to assess associations between metabolic risk factors and sleep and activity parameters. Results On average, participants went to bed at 00:22±0.88 hours and slept 6.2±0.7 hours/night, with 0.83±0.36 hours of awakenings/night. However, night-tonight variability in sleep duration (0.87±0.57 hours) and bedtime (0.79±0.58 hours) was considerable. Neither average sleep duration nor mean bedtime was associated with any metabolic risk factors. However, greater night-tonight variability in sleep duration was associated with higher total body (β=1.9±0.9 .

Research paper thumbnail of Changes in sleep and activity from age 15 to 17 in students with traditional and college-style school schedules

Sleep Health, Dec 1, 2020

Objectives:Sleep duration and physical activity decline with age during adolescence. Earlier scho... more Objectives:Sleep duration and physical activity decline with age during adolescence. Earlier school schedules may contribute to these declines. The aim of this longitudinal study was to track changes in sleep and activity of Icelandic youth from primary to secondary school and compare students who enrolled in secondary schools with traditional and college-style schedules.Methods:We measured free-living sleep and activity with wrist actigraphy and body composition by dual-energy x-ray absorptiometry in 145 students at age 15 and age 17, when 58% attended schools with college-style scheduling. Differences from 15 to 17 and between students of different school structures were assessed with mixed-effect models.Results:Actigraphs were worn for 7.1±0.4 nights at 15 and 6.9±0.4 nights at 17. Overall, sleep duration decreased from 6.6±0.7 h/night to 6.2±0.7 h/night from age 15 to 17 (p<0.001). Students with traditional schedules reduced school-night sleep duration 26 min/night at follow-up (p<0.001), while sleep duration did not change for college-style students. All students went to bed later on school nights at follow-up, but only college-style students rose later. Sleep efficiency and awakenings did not differ by schedule-type. Neither sex changed body fat percentage, but average school-day activity decreased by 19% (p<0.001) on follow-up and did not differ by schedule-type.Conclusions:Over the two-year period, adolescents decreased weekly sleep duration and activity, but only those continuing traditional schedules reduced school-night sleep. This suggests greater individual control of school schedule may preserve sleep duration in this age group, which may be beneficial during the transition into adulthood.

Research paper thumbnail of Less screen time and more physical activity is associated with more stable sleep patterns among Icelandic adolescents

Sleep Health, Oct 1, 2020

Objectives: Emerging evidence suggests that inconsistent sleep may affect physical and psychologi... more Objectives: Emerging evidence suggests that inconsistent sleep may affect physical and psychological health. Thus, it is important to identify modifiable determinants of sleep variability. Screen time and physical activity are both thought to affect sleep, but studies of their relationship to sleep variability using objective measures are lacking. We examined cross-sectional associations between these variables in mid-teen adolescents using objectively measured sleep and activity. Methods: Wrist-worn accelerometers were used to measure one week of sleep and activity in 315 tenth grade students (mean age 15.8y) from six Reykjavik compulsory schools. Participants reported their daily hours of screen time. Regression analysis was used to explore associations of screen time and physical activity with variability in duration, quality, and timing of sleep, adjusting for DXA-measured body fat percentage, parental education, and physical activity or screen time.

Research paper thumbnail of 0105 Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents

Sleep, May 25, 2022

and Digestive and Kidney Diseases 2 0Introduction: Sleep has been shown to affect cognitive funct... more and Digestive and Kidney Diseases 2 0Introduction: Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self-reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free-living sleep quantity, quality, and timing of 15-year-old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement. Methods: We measured sleep with wrist actiography for 1 week in 253 (150 girls) Icelandic adolescents with a mean (SD) age of 15.9 (0.3) years. Multiple linear regression was used to assess associations between sleep parameters and combined standardised examination scores in mathematics, English, and Icelandic obtained from the Icelandic Directorate of Education. Results: We found that students went to bed at 00:49 hours (± 51.8 min) and slept for a mean (SD) of 6.6 (0.7) hr/night, with a median (interquartile range) night-tonight variation in sleep duration of 1.2 (0.7) hr and an efficiency of 88.1 (5.3)%. Combined analyses adjusted for sex, demonstrated that both bedtime and night-tonight variability in total sleep time were negatively associated with the average score across all topics. Sex-specific associations did not indicate clear differences between boys and girls. Conclusion: These findings suggest that, in addition to appropriate sleep duration, public health guidance should also highlight the importance of early and consistent sleep schedules to academic achievement for both boys and girls.

Research paper thumbnail of Sleeping Behavior and Physical Health of Icelandic Adolescents

Research paper thumbnail of Screen Time and Body Image in Icelandic Adolescents: Sex-Specific Cross-Sectional and Longitudinal Associations

International Journal of Environmental Research and Public Health, Jan 24, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Organized Sport Participation, Physical Activity, Sleep and Screen Time in 16-Year-Old Adolescents

International Journal of Environmental Research and Public Health, Mar 18, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Svefn, hreyfing og heilsa íslenskra ungmenna

Background Sleep and physical activity are essential functions of human health. According to Inte... more Background Sleep and physical activity are essential functions of human health. According to International recommendations, adolescents should sleep 8-10 hours each night and engage in moderate to vigorous physical activity for at least 60 minutes per day for overall wellbeing. Previous studies have shown that during adolescence, sleep patterns change and most sleep studies up to date are based on subjective data for sleep duration and quality. Technological advancement in measurement of sleep and physical activity with objective measures adds value to the literature. Aim The main aim of the dissertation was to measure free-living sleep and physical activity in Icelandic youth at baseline (15 years) and two years later (17 years), and explore associations between sleep (duration, quality and timing), physical activity, and body composition. In addition, to compare sensitivity and agreement between subjective and objective measurements of sleep among and between ages of 15 and 17 yea...

Research paper thumbnail of Henta lágkolvetnamataræði og föstur í þjálfun?