Tracy Nelson | Colorado State University (original) (raw)

Papers by Tracy Nelson

Yokoyama, Yoshie; Jelenkovic, Aline; Sund, Reijo; Sung, Joohon; Hopper, John L; Ooki, Syuichi; He... more Yokoyama, Yoshie; Jelenkovic, Aline; Sund, Reijo; Sung, Joohon; Hopper, John L; Ooki, Syuichi; Heikkilä, Kauko; Aaltonen, Sari; Tarnoki, Adam D; Tarnoki, David L; Willemsen, Gonneke; Bartels, Meike; van Beijsterveldt, Toos C E M; Saudino, Kimberly J; Cutler, Tessa L; Nelson, Tracy L; Whitfield, Keith E; Wardle, Jane; Llewellyn, Clare H; Fisher, Abigail; He, Mingguang; Ding, Xiaohu; Bjerregaard-Andersen, Morten; Beck-Nielsen, Henning; Sodemann, Morten; Song, Yun-Mi; Yang, Sarah; Lee, Kayoung; Jeong, Hoe-Uk; KnafoNoam, Ariel; Mankuta, David; Abramson, Lior; Burt, S Alexandra; Klump, Kelly L; Ordoñana, Juan R; Sánchez-Romera, Juan F; Colodro-Conde, Lucia; Harris, Jennifer R; Brandt, Ingunn; Nilsen, Thomas Sevenius; Craig, Jeffrey M; Saffery, Richard; Ji, Fuling; Ning, Feng; Pang, Zengchang; Dubois, Lise; Boivin, Michel; Brendgen, Mara; Dionne, Ginette; Vitaro, Frank; Martin, Nicholas G; Medland, Sarah E; Montgomery, Grant W; Magnusson, Patrik K E; Pedersen, Nancy L; Aslan, Anna K Dahl;...

Obesity, 2019

ObjectiveThe objective of this study was to analyze how parental education modifies the genetic a... more ObjectiveThe objective of this study was to analyze how parental education modifies the genetic and environmental variances of BMI from infancy to old age in three geographic‐cultural regions.MethodsA pooled sample of 29 cohorts including 143,499 twin individuals with information on parental education and BMI from age 1 to 79 years (299,201 BMI measures) was analyzed by genetic twin modeling.ResultsUntil 4 years of age, parental education was not consistently associated with BMI. Thereafter, higher parental education level was associated with lower BMI in males and females. Total and additive genetic variances of BMI were smaller in the offspring of highly educated parents than in those whose parents had low education levels. Especially in North American and Australian children, environmental factors shared by co‐twins also contributed to the higher BMI variation in the low education level category. In Europe and East Asia, the associations of parental education with mean BMI and BM...

Twin research and human genetics : the official journal of the International Society for Twin Studies, 2016

We analyzed birth order differences in means and variances of height and body mass index (BMI) in... more We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.5 to 79.5 years of age was 397,466. As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood. After adjusting the results for birth weight, the birth order differences decreased and were no longer statistically significant. First-born twins had greater BMI than the second-born twins over childhood and adolescence. After adjusting the results for birth weight, birth order was still associated with BMI until 12 years of age. No interaction effect between birth order and zygosity was found. Only limited evidence was found that birth order influenced variances of height or BMI. The results wer...

Twin research and human genetics : the official journal of the International Society for Twin Studies, Jan 4, 2015

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been sugges... more A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than ...

Obesity Research, 2002

Genetic and environmental influences on body-fat measures among African-American twins. Obes Res.... more Genetic and environmental influences on body-fat measures among African-American twins. Obes Res. 2002;10:733-739. Objective: To investigate the genetic and environmental influences on body-fat measures including waist circumference (WC), waist-to-hip ratio (WHR), and body mass index (BMI) among African-American men and women. Research Methods and Procedures: Measurements were taken as part of the Carolina African American Twin Study of Aging. This sample currently comprises 146 same-sex African-American twins with an average age of 50 years (range, 22 to 88 years). This analysis included 26 monozygotic and 29 dizygotic men and 45 monozygotic and 46 dizygotic women. Maximum likelihood quantitative genetic analysis was used. Results: In men, additive genetic effects accounted for 77% of the variance in WC, 59% in WHR, and 89% in BMI. In women, additive genetic effects accounted for 76% of the variance in WC, 56% in WHR, and 73% in BMI. The remaining variance in both men and women was attributed to unique environmental effects (WC, 21%; WHR, 36%; BMI, 11% in men and WC, 22%; WHR, 38%; BMI, 27% in women) and age (WC, 2%; WHR, 5% in men and WC, 2%; WHR, 6% in women). When BMI was controlled in the analysis of WC and WHR, it accounted for a portion of the genetic and environmental variance in WHR and over onehalf of the genetic and environmental variance in WC. Discussion: There are both genetic and environmental influences on WC, WHR, and BMI, and independent of BMI, there are genetic and environmental effects on WC and WHR among both genders. The results from this African-American twin sample are similar to findings among white twin samples.

The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 1999

Background. As people age, fat becomes preferentially deposited in the abdominal region over the ... more Background. As people age, fat becomes preferentially deposited in the abdominal region over the periphery, and such changes are thought to be associated with adverse metabolic outcomes. We were interested in whether body mass index (EMI) and waist-hip ratio (WHR) are differentially associated with fasting insulin levels, triglycerides, and blood pressure (systolic and diastolic) in an older population. We were also interested in whether these associations change after controlling for genetic influences. Methods. Data were obtained as part of the Swedish Adoption/fwin Study of Aging. All blood samples and anthropometric measures were assessed from 1989-1991 except insulin, which was assessed from 1986-1988. The sample contains 263'twin pairs (97 monozygotic and 166 dizygotic), 56% women, average age 65 years. Results. In men and women, WHR and BMI were significantly associated with all the metabolic variables except for diastolic blood pressure. When BMI's association with the metabolic variables was assessed independent ofWHR, it remained significantly associated with all metabolic variables except diastolic blood pressure in men and triglycerides in women. When WHR's association with the metabolic variables was assessed independent of BMI, it did not remain significantly associated with any of the metabolic variables in men and remained significantly associated with insulin and diastolic pressure in women. After controlling for genetic effects, the relationship between WHR and the metabolic variables became nonsignificant. However, BMI remained significantly associated with systolic blood pressure and triglycerides in men, independent ofWHR, Conclusion. The results suggest that overall body fat is important to consider in relation to these metabolic parameters in older individuals. The results also suggest that BMI may share associations with blood pressure and triglycerides beyond those that can be attributed to familial influences.

European Journal of Epidemiology, 2012

Increased body mass index (BMI) is a worldwide health issue. Individual differences in the suscep... more Increased body mass index (BMI) is a worldwide health issue. Individual differences in the susceptibility to increased BMI could be related to genes or environment. We performed a systematic review of genetic studies on BMI in pre-adolescence, young adulthood and late adulthood. We searched PubMed and EMBASE with heritability, body mass index, BMI, weight, height, anthropometry and twins as search terms. Studies reporting intra-pair correlations of healthy twin pairs that were raised together were included. This resulted in the inclusion of 8,179 monozygotic (MZ) and 9,977 dizygotic (DZ) twin pairs from twelve published studies in addition to individual participant data for 629 MZ and 594 DZ pairs from four twin registries. Structural equation modelling with intra-pair twin correlations showed that the heritability of BMI remained high over all age categories ranging from 61 % (95 % CI 54-64 %) to 80 % (95 % CI 76-81 %) for male and female subjects combined, while unique

Twin Research and Human Genetics, 2019

The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) projec... more The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m2) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and leng...

Occupational Medicine, Jul 3, 2009

Background The leading cause of mortality in on-duty firefighters is sudden cardiac death. While ... more Background The leading cause of mortality in on-duty firefighters is sudden cardiac death. While the reason for this remains unclear, low cardiorespiratory fitness and the metabolic syndrome have been associated with increased risk of cardiovascular disease-related events. Aims To document the levels of cardiorespiratory fitness and the metabolic syndrome, as well as to determine if there is a relationship between these variables, in firefighters. Methods Maximal cardiorespiratory fitness was assessed using the Bruce treadmill protocol in 214 male firefighters from Colorado. As part of a comprehensive cardiovascular disease risk evaluation, each firefighter was also screened for the metabolic syndrome using the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATP III) guidelines. Results At the time of their evaluation, 32 firefighters (15%) met the NCEP/ATP III diagnostic criteria for the metabolic syndrome, and 54 firefighters (25%) failed to achieve a generally accepted minimum cardiorespiratory fitness level of 42.0 ml/kg/min. A significant inverse trend of increasing cardiorespiratory fitness with decreasing metabolic abnormalities was found (P , 0.001). Conclusions Increased levels of cardiorespiratory fitness are associated with an improved metabolic profile in male firefighters. Comprehensive cardiovascular disease risk factor management and cardiorespiratory fitness improvement are essential for firefighter health and safety.

Psychology of Sport and Exercise, 2021

We examined the associations of autonomous motivation, controlled motivation, and physical activi... more We examined the associations of autonomous motivation, controlled motivation, and physical activity (PA) planning with PA participation over six years across the adolescent-to-adult transition. Participants from the NEXT Generation Health Study, a nationally representative cohort study of U.S. 10th graders (N = 2785), completed surveys yearly from 2010 to 2016 (four years post-high school). This study used data from Waves 2 (W2) through 7 (W7). Data were analyzed using growth models accounting for the complex survey design and controlling for sex, race/ethnicity, and body mass index. A piecewise growth model with two pieces (Piece 1: W2-W4; Piece 2: W4-W7) indicated that PA declined during late adolescence (W2-W4) (b = − 0.31, β = − 0.22, p < .001), but did not decline after the transition into early adulthood (W4-W7) (b = − 0.08, β = − 0.04, p = .052). Autonomous motivation was positively associated with PA at all waves (b = 0.23-0.33, β = 1.90-4.37, p < .001). Controlled motivation was only positively associated with PA at W3 (12th grade) (b = 0.13, β = 1.54, p = .011). PA planning varied significantly between individuals and significantly predicted PA (b = 0.44, β = 0.21, p < .001). Although PA decreased significantly during late adolescence, PA did not decrease significantly after transitioning into early adulthood (one to four years post-high school). Elevated autonomous motivation and PA planning were consistently and significantly associated with higher PA, suggesting that these may be useful intervention targets during this adolescent-to-adult transition.

Hormones and Behavior, 2021

Comparing twins from same-and opposite-sex pairs can provide information on potential sex differe... more Comparing twins from same-and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same-and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (β = − 0.05 educational years, 95% CI − 0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an oppositesex co-twin (β = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between samesex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.

Scientific Reports, 2020

We investigated the heritability of educational attainment and how it differed between birth coho... more We investigated the heritability of educational attainment and how it differed between birth cohorts and cultural–geographic regions. A classical twin design was applied to pooled data from 28 cohorts representing 16 countries and including 193,518 twins with information on educational attainment at 25 years of age or older. Genetic factors explained the major part of individual differences in educational attainment (heritability: a2 = 0.43; 0.41–0.44), but also environmental variation shared by co-twins was substantial (c2 = 0.31; 0.30–0.33). The proportions of educational variation explained by genetic and shared environmental factors did not differ between Europe, North America and Australia, and East Asia. When restricted to twins 30 years or older to confirm finalized education, the heritability was higher in the older cohorts born in 1900–1949 (a2 = 0.44; 0.41–0.46) than in the later cohorts born in 1950–1989 (a2 = 0.38; 0.36–0.40), with a corresponding lower influence of comm...

International Journal of Environmental Research and Public Health, 2019

The combination of poor diet and exposure to secondhand smoke may increase hemoglobin A1c (HbA1c)... more The combination of poor diet and exposure to secondhand smoke may increase hemoglobin A1c (HbA1c) levels, but few studies have explored this interaction. We explored an interaction among 574 never-smoking adults from the Singapore Chinese Health Study. At baseline (age 59 ± 8 years), intakes of omega-3 polyunsaturated fatty acids, vitamin C, vitamin E and fiber were estimated using a modified food frequency questionnaire. At follow-up (age 64 ± 9 years), HbA1c and cotinine were measured. A product term between cotinine (above or below the median value) and each nutrient (high or low intake) was included in separate linear regression models with HbA1c as the outcome. HbA1c among those with high cotinine and low omega-3 polyunsaturated fatty acids intakes were higher than would be expected due to the individual effects alone (p-for-interaction = 0.05). Among those with lower intakes of omega-3 polyunsaturated fatty acids, high cotinine levels were associated with 0.54% higher HbA1c le...

The Journal of Primary Prevention, 2019

International Journal of Obesity, 1999

OBJECTIVE: To investigate the genetic and environmental in¯uences on waist-to-hip ratio (WHR) and... more OBJECTIVE: To investigate the genetic and environmental in¯uences on waist-to-hip ratio (WHR) and waist circumference (WC) measurements in males and females. DESIGN: Measurements taken from 1989 ± 1991 as part of The Swedish AdoptionaTwin Study of Aging (SATSA) were used for analysis. The SATSA sample contains both twins reared together as well as twins reared apart. SUBJECTS: 322 pairs of twins (50 identical, 82 fraternal male pairs and 67 identical, 123 fraternal female pairs); age range: 45 ± 85 y (average age, 65 y). MEASUREMENTS: Waist-to-hip ratio (WHR), waist circumference (WC) and body mass index (BMI). RESULTS: In males, additive genetic effects were found to account for 28% of the variance in WHR and 46% of the variance in WC. In females, additive genetic effects were found to account for 48% of the variance in WHR and 66% of the variance in WC. The remaining variance in males was attributed to unique environmental effects (WHR, 72%; WC, 54%) and in females the remaining variance was attributed to unique environmental effects (WHR, 46%; WC, 34%) and age (WHR, 6%). When BMI was added into these models it accounted for a portion of the genetic and environmental variance in WHR, and over half of the genetic and environmental variance in WC. CONCLUSION: There are both genetic and environmental in¯uences on WHR and WC, independent of BMI in both males and females, and the differences between the sexes are signi®cantly different.

The American journal of clinical nutrition, Jan 5, 2017

Background: Genes and the environment contribute to variation in adult body mass index [BMI (in k... more Background: Genes and the environment contribute to variation in adult body mass index [BMI (in kg/m(2))], but factors modifying these variance components are poorly understood.Objective: We analyzed genetic and environmental variation in BMI between men and women from young adulthood to old age from the 1940s to the 2000s and between cultural-geographic regions representing high (North America and Australia), moderate (Europe), and low (East Asia) prevalence of obesity.Design: We used genetic structural equation modeling to analyze BMI in twins ≥20 y of age from 40 cohorts representing 20 countries (140,379 complete twin pairs).Results: The heritability of BMI decreased from 0.77 (95% CI: 0.77, 0.78) and 0.75 (95% CI: 0.74, 0.75) in men and women 20-29 y of age to 0.57 (95% CI: 0.54, 0.60) and 0.59 (95% CI: 0.53, 0.65) in men 70-79 y of age and women 80 y of age, respectively. The relative influence of unique environmental factors correspondingly increased. Differences in the sets ...

Age and Ageing, 2016

Objective: we investigated the association between the peroxisome proliferator-activated receptor... more Objective: we investigated the association between the peroxisome proliferator-activated receptor (PPAR)-gamma Pro12Ala polymorphism and cognitive decline in older adults. Methods: participants from a population-based cohort of older Hispanic and non-Hispanic white adults (n = 492) were administered the Mini Mental State Examination (MMSE), a multi-domain cognitive screening tool, and the Behavioral Dyscontrol Scale (BDS), a measure of executive cognitive function, at baseline and at follow-up, an average of 22 months later. Multiple linear regression was used to investigate the association between the two cognitive test scores and the Pro12Ala polymorphism. Results: at baseline, presence of the Ala12 allele was not significantly associated with MMSE score (P = 0.62) nor with BDS score (P = 0.85). Heterogeneity was present for cognitive decline as measured by the MMSE among ethnic, sex and Ala12 allele status (P = 0.04 for three-way interaction term). Stratification by the cross-classification of sex and ethnicity revealed significantly greater declines in MMSE score among male Hispanic carriers of the Ala12 allele compared to male Hispanic non-carriers (decline = 4.0 versus 1.6 points; P = 0.02). A significant difference in decline between Ala12 carriers and non-carriers was not present among the other sex/ethnic groups. Conclusions: carriers of the PPAR-γ Ala12 allele showed greater cognitive decline compared to non-carriers as detected by the MMSE but the risk varied across sex and ethnic groups. Male Ala12 carriers of Hispanic origin may be a high-risk group for cognitive decline.

Endocrine, Metabolic & Immune Disorders - Drug Targets, 2010

International Journal of Environmental Health Research, 2009

and-conditions-of-access.pdf This article may be used for research, teaching and private study pu... more and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Twin research and human genetics : the official journal of the International Society for Twin Studies, Jan 27, 2015

For over 100 years, the genetics of human anthropometric traits has attracted scientific interest... more For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We a...