Differential secular trends in BMI in relation to region of childhood residence: A 25 year follow-up of a nationally representative sample

Although regional variations in prevalence of overweight and average BMI have been well documented, the relationship between childhood region of residence and BMI in adulthood remains poorly understood. This study aimed to estimate secular trends in BMI among US adults and to examine these trends in relation to region of residence in childhood and adulthood. Using 16 waves of nationally representative data from The National Longitudinal Survey of Youth 1979 (n=12,686), the study examined the change in individuals' BMI over 25 years using random effects models. We found an independent positive association between years of residence in the South during childhood and adolescence (age 14), and secular trends in overweight during adolescence and adulthood (ß = .08, p =.05). In line with previous studies, the average BMI among men overall increases by 0.07~0.34 kg/m2 and the odds of being overweight increases multiplicatively by 3~12% (obese: 4~10%) over each birth cohort year. Among women, the average BMI increases by 0.14~0.21 kg/m2 and the odds of being overweight increases by -2~8% (obese: -6~10%). These increasing trends are significant for both genders among whites and among all races combined. The secular trend in BMI for respondents who resided in the South during childhood is elevated in comparison to the trend for other respondents, suggesting an independent association between childhood region of residence and trends in BMI during adulthood. This is the most precise and detailed epidemiologic study to date to examine secular trends in BMI among US residents in relation to regional differences.