Timing and Duration of Obesity in Relation to Diabetes: Findings from an ethnically diverse, nationally representative sample

NATALIE S. THE PHD ANDREA S. RICHARDSON PENNY GORDON-LARSEN PHD E p i d e m i o l o g y / H e a l t h OBJECTIVEdThe influence on diabetes of the timing and duration of obesity across the highrisk period of adolescence to young adulthood has not been investigated in a population-based, ethnically diverse sample. RESEARCH DESIGN AND METHODSdA cohort of 10,481 individuals aged 12-21 years enrolled in the U.S. National Longitudinal Study of Adolescent Health (1996) was followed over two visits during young adulthood (18-27 years, 2001-2002; 24-33 years, 2007-2009). Separate logistic regression models were used to examine the associations of diabetes (A1C $6.5% or diagnosis by a health care provider) in young adulthood with 1) obesity timing (never obese, onset ,16 years, onset 16 to ,18 years, onset $18 years) and 2) obesity duration over time (never obese, incident obesity, fluctuating obesity, and persistent obesity), testing differences by sex and race/ethnicity. RESULTSdAmong 24- to 33-year-old participants, 4.4% had diabetes (approximately half were undiagnosed), with a higher prevalence in blacks and Hispanics than whites. In multivariable analyses, women who became obese before age 16 were more likely to have diabetes than women who became obese at or after age 18 (odds ratio 2.77 [95% CI 1.39-5.52]), even after accounting for current BMI, waist circumference, and age at menarche. Persistent (vs. adult onset) obesity was associated with increased likelihood of diabetes in men (2.27 [1.41-3.64]) and women (2.08 [1.34-3.24]). CONCLUSIONSdDiabetes risk is particularly high in individuals who were obese as adolescents relative to those with adult-onset obesity, thus highlighting the need for diabetes prevention efforts to address pediatric obesity. - D stantially over the last few decades, iabetes prevalence has risen subdisproportionately affecting racial/ ethnic minorities (1,2). In 2007, 24 million Americans had diabetes; nearly 6 million were undiagnosed (3). The total cost of diabetes in 2007 was estimated to be $174 billion (4), and this economic burden is likely to escalate over time. The adverse health and economic consequences combined with significant racial/ ethnic disparities and high rates of undiagnosed diabetes emphasize the critical need to address this disease. Although the links between current obesity and type 2 diabetes are clear, some research suggests that a history of obesity during childhood (5,6) and young adulthood (7) increases diabetes risk later in life. However, the differential and cumulative effects of obesity during different periods of the life span on the development of diabetes are not well documented. In particular, adolescence may be a sensitive period for the development of diabetes given the substantial decreases in insulin sensitivity associated with pubertal development (8). This period has c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c the potential for alterations in insulin metabolism, which might increase diabetes risk later in life, and there is the potential that a longer duration of obesity might elicit additional metabolic changes that increase future diabetes risk (9,10). With obesity, pancreatic b-cells initially increase insulin release to overcome the reduced efficiency of insulin action, although over time compensation may become insufficient, ultimately leading to the development of diabetes (9,10). Nevertheless, epidemiologic research specifically examining the relationship between duration of obesity with diabetes in adulthood has yielded inconsistent results (1116). A better understanding of the relationship of obesity timing and duration to diabetes in adulthood is needed to determine important periods for diabetes intervention, particularly in diverse ethnic groups. In this article, we use nationally representative, longitudinal data to examine racial/ethnic differences in rates of diagnosed and undiagnosed diabetes in young adults. In addition, we capitalize upon longitudinal data to examine how adolescent-onset obesity and adult-onset obesity might differentially relate to diabetes risk in young adulthood and whether these associations differ by sex and race/ethnicity. We hypothesize that individuals who experienced adolescent(vs. adult onset) obesity would be more likely to have diabetes in young adulthood, independent of current body size, with the highest risk among those with persistent obesity from the teen to adult years. RESEARCH DESIGN AND METHODS National Longitudinal Study of Adolescent Health The National Longitudinal Study of Adolescent Health (Add Health) is a cohort of adolescents (N = 20,745; ages 1121 years), representative of the U.S. school population in grades 7 to 12 in 1994 1995 (wave I) and followed into young adulthood. Wave II (1996; n = 14,738; ages 1222 years) included wave I adolescents who had not graduated from high school (including those who had dropped out of high school). Wave III (20012002; n = 15,197; ages 1828 years) and wave IV (20082009; n = 15,601; ages 2434 years) followed all wave I respondents regardless of wave II participation. Survey procedures have been described elsewhere (17) and were approved by the institutional review board at the University of North Carolina at Chapel Hill. Our primary inclusion criterion was that respondents were seen during wave IV (n = 15,601). We excluded individuals without a longitudinal sampling weight (n = 801), which was needed to correct for nonresponse bias and sample design (18), ultimately resulting in 14,800 eligible individuals. In addition, we excluded Native Americans (n = 59) because of the small sample size and individuals who were missing the following data: diabetes status at wave IV (n = 113), measured height and weight at two or more waves (n = 1,221 [measured data not available at wave I]), family history of diabetes (n = Table 1dPrevalence of each diabetes group by sociodemographic and anthropometric characteristics of the analytic sample, from the National Longitudinal Study of Adolescent Health, waves II through IV (N = 10,481) 2,839), or demographic data (n = 87). Our final analytic sample included 10,481 individuals. Comparing the 15,601 eligible participants included in our analytic sample with the missing 5,120, we observed significant differences by race/ethnicity, education, age, and sex. To assess selection bias, we used inverse probability weighting (IPW), which assigns a weight to each subject in the analytic sample so each subject accounts for himself or herself in the analysis as well as those with similar characteristics who were not selected into our final analytic sample (19). For each participant, we estimated a weight proportional to the inverse of the probability of being in our analytic sample. We used two separate multivariable, logistic models to predict diabetes at wave IV as a function of obesity (timing or duration), race/ethnicit (...truncated)