Differential Sleep, Sleepiness, and Neurophysiology in the Insomnia Phenotypes of Shift Work Disorder (original) (raw)
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The Nature of Stable Insomnia Phenotypes
SLEEP, 2015
We examined the 1-y stability of four insomnia symptom profiles: sleep onset insomnia; sleep maintenance insomnia; combined onset and maintenance insomnia; and neither criterion (i.e., insomnia cases that do not meet quantitative thresholds for onset or maintenance problems). Insomnia cases that exhibited the same symptom profile over a 1-y period were considered to be phenotypes, and were compared in terms of clinical and demographic characteristics. Design: Longitudinal. Setting: Urban, community-based. Participants: Nine hundred fifty-four adults with Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition based current insomnia (46.6 ± 12.6 y; 69.4% female). Interventions: None. Measurements and results: At baseline, participants were divided into four symptom profile groups based on quantitative criteria. Follow-up assessment 1 y later revealed that approximately 60% of participants retained the same symptom profile, and were hence judged to be phenotypes. Stability varied significantly by phenotype, such that sleep onset insomnia (SOI) was the least stable (42%), whereas combined insomnia (CI) was the most stable (69%). Baseline symptom groups (cross-sectionally defined) differed significantly across various clinical indices, including daytime impairment, depression, and anxiety. Importantly, however, a comparison of stable phenotypes (longitudinally defined) did not reveal any differences in impairment or comorbid psychopathology. Another interesting finding was that whereas all other insomnia phenotypes showed evidence of an elevated wake drive both at night and during the day, the "neither criterion" phenotype did not; this latter phenotype exhibited significantly higher daytime sleepiness despite subthreshold onset and maintenance difficulties. Conclusions: By adopting a stringent, stability-based definition, this study offers timely and important data on the longitudinal trajectory of specific insomnia phenotypes. With the exception of daytime sleepiness, few clinical differences are apparent across stable phenotypes.
Sleep and circadian rhythm disturbances: multiple genes and multiple phenotypes
Current Opinion in Genetics & Development, 2009
Sleep is regulated by two broad mechanisms: the circadian system, which generates 24-h rhythms of sleep propensity and a wake-dependent homeostatic sleep process whereby sleep pressure increases during wake and dissipates during sleep. These, in turn, regulate multiple brain structures and neurotransmitter systems. In view of the complexity of sleep it is not surprising that there is considerable variation between individuals in both sleep timing and propensity. Furthermore, marked abnormalities in sleep are commonly encountered in psychiatric and neurodegenerative disorders. Teasing apart the genetic versus environmental contributions to normal and abnormal sleep is complex. Here we attempt to summarise what recent progress has been made, and what will be needed in the future to gain a more complete understanding of this fundamental aspect of physiology.
Assessment of biological components associated with sleepiness in young working college students
2012
Objectives: An association, responsible for affecting circadian rhythms and sleep homeostasis, between PER3 gene variable number tandem repeat (VNTR) and sleep times has been described in humans. The aim of this study was to evaluate the association between clock genes VNTR and sleep duration, chronotype and melatonin secretion. Methods: A hundred forty-six students filled a questionnaire about their sleep habits to determine individual preferences. Salivary samples were also collected for DNA extraction. PER3 VNTR was genotyped using PCR. Results: Seventy subjects were PER3 4/4 (47.9%), 61 PER3 4/5 (41.8%) and 15 PER3 5/5 (10.3%). Mean sleep duration of PER3 5/5 , intermediate chronotype students (8h) was higher than PER3 4/4 , morningness chronotype (5:58h). On days-off, for evening-types, sleep outset was delayed (10:44h) when compared to morning-types (09:38h). Part of the students took part in a study about bright light intervention and its effects upon sleepiness. When exposed to bright light at 19:00h, the students' sleepiness growth went as expected. But, when exposed at 21:00h, sleepiness slightly increased for the intermediates and decreased at 22:00h for the evening-type students. Analyzing PER3 and HIOMT genotypes a specific haplotype, associated to melatonin levels at 19:00h and after bright light exposure, at 19:20h, was detected. Conclusion: With no social restrictions for sleep onset/ outset, chronotypes express different sleep preferences, partly associated to PER3 VNTR genotype.
Shift work is associated with extensively disordered sleep, especially when working nights
Frontiers in Psychiatry, 2023
Background: Shift work is generally associated with working and sleeping out of phase with the endogenous, circadian sleep-wake cycle. This exerts detrimental effects on sleep health. The present study aimed at evaluating the presence of short and long sleep as well as sleep disorders within a broad range of shift work schedules and elucidating the role of sociodemographic factors therein. Methods: A large dataset containing information on sleep was collected through advertisement in a Belgium newspaper (De Standaard). Adult, working individuals were selected (n = 37,662) and categorized based on their work schedule (regular day, early morning, evening, night, and rotating shift). In this cross-sectional study, prevalence rates of short sleep (≤6 h), long sleep (≥9 h) and sleep disorders (screened with Holland Sleep Disorders Questionnaire), and associations between these sleep variables and sociodemographics (age, sex, education, living companion(s)) were analyzed using binominal logistic regression analyses. Results: In the total sample all sociodemographic factors affected prevalences of short, long and disordered sleep, consistent with previous studies. Compared to day workers, shift workers more frequently reported short sleep, most prominently night workers (26 vs. 50%) (p < 0.001). Furthermore, all sleep disorders as well as sleep disorder comorbidity were more common in shift workers, again most pronounced in night workers (all p < 0.05). In night shift workers the level of education had the strongest associations with disturbed sleep with a twofold higher prevalence of short and disordered sleep in low relative to academic educated groups (all p < 0.02). Conclusion: Shift work is related not only to curtailed sleep and shift work disorder, but also to a plethora of sleep disorders, including insomnia, sleeprelated breathing disorders and sleep-related movement disorders. Our findings imply that education on coping strategies may be especially important for young and/or lower educated shift workers.
2004
contrast, there have been a number of laboratory and field studies that have focused on the effects of shiftwork schedules on sleep and alertness. Overall, these studies have shown that individuals engaged in shift work experience disturbed sleep and excessive sleepiness relative to day workers. 3-9 These symptoms are likely due to the fact that shift workers' behavioral sleep-wake schedules are out of phase and often in direct opposition to their endogenous circadian rhythms. 9-12 The human circadian timing system is tightly entrained by exposure to environmental light. 13,14 Normally, environmental light maintains circadian entrainment to the 24-hour day. Late evening light will phase delay rhythms while morning light will advance them. 15,16 However, shifts in endogenous rhythms are difficult to maintain except under laboratory conditions where light exposure is restricted to atypical periods of the day and night. 17-20 Even in tightly controlled experiments using bright light to shift circadian rhythms, more than 30% of shift workers are unable to attain large phase shifts. 21,22 Difficulty limiting light exposure to appropriate times of day is a major reason why most shift workers, even those on permanent night shifts, do not fully
Sleepiness during night-shift – sleeping habits or melatonin rhythm? A laboratory study
International Journal of Industrial Ergonomics, 2000
This study examined the relation between individual sleeping habits, and sensitivity to sleepiness during "ve simulated night-shifts. Seventeen male volunteers were selected by their features of`morningness}eveningnessa and #exibility or rigidity of sleeping habits. Subjective scales of sleepiness and fatigue, mental performance, sleep, attenuation alpha test and the melatonin circadian rhythm were measured. Data analysis compared the following groups: evening}morning, #exible}rigid, evening}#exible, morning}#exible and morning}rigid groups, and two other de"nite groups from the total sample: a "rst group with an advanced onset of melatonin production at 23:00 and a second group (delayed onset) at 02:00. Results showed that morning, morning}#exible, morning}rigid and advance groups presented more adjustment di$culties than evening, evening}#exible and delay groups. Di!erences between #exible and rigid subjects remained less pronounced because of the heterogeneity of samples. The results of this preliminary study suggest that melatonin production and a combination of the two dimensions`eveningnessa and`#exibilitya of sleeping habits could explain the capacity to adjust to night-work.