Adolescent BMI trajectory and risk of diabetes versus coronary disease

Abstract

Background: The association of body-mass index (BMI) from adolescence to adulthood with obesity-related diseases in young adults has not been completely delineated.

Methods: We conducted a prospective study in which we followed 37,674 apparently healthy young men for incident angiography-proven coronary heart disease and diabetes through the Staff Periodic Examination Center of the Israeli Army Medical Corps. The height and weight of participants were measured at regular intervals, with the first measurements taken when they were 17 years of age.

Results: During approximately 650,000 person-years of follow-up (mean follow-up, 17.4 years), we documented 1173 incident cases of type 2 diabetes and 327 of coronary heart disease. In multivariate models adjusted for age, family history, blood pressure, lifestyle factors, and biomarkers in blood, elevated adolescent BMI (the weight in kilograms divided by the square of the height in meters; mean range for the first through last deciles, 17.3 to 27.6) was a significant predictor of both diabetes (hazard ratio for the highest vs. the lowest decile, 2.76; 95% confidence interval [CI], 2.11 to 3.58) and angiography-proven coronary heart disease (hazard ratio, 5.43; 95% CI, 2.77 to 10.62). Further adjustment for BMI at adulthood completely ablated the association of adolescent BMI with diabetes (hazard ratio, 1.01; 95% CI, 0.75 to 1.37) but not the association with coronary heart disease (hazard ratio, 6.85; 95% CI, 3.30 to 14.21). After adjustment of the BMI values as continuous variables in multivariate models, only elevated BMI in adulthood was significantly associated with diabetes (β=1.115, P=0.003; P=0.89 for interaction). In contrast, elevated BMI in both adolescence (β=1.355, P=0.004) and adulthood (β=1.207, P=0.03) were independently associated with angiography-proven coronary heart disease (P=0.048 for interaction).

Conclusions: An elevated BMI in adolescence--one that is well within the range currently considered to be normal--constitutes a substantial risk factor for obesity-related disorders in midlife. Although the risk of diabetes is mainly associated with increased BMI close to the time of diagnosis, the risk of coronary heart disease is associated with an elevated BMI both in adolescence and in adulthood, supporting the hypothesis that the processes causing incident coronary heart disease, particularly atherosclerosis, are more gradual than those resulting in incident diabetes. (Funded by the Chaim Sheba Medical Center and the Israel Defense Forces Medical Corps.).

Figure 1. Trajectory of BMI from Adolescence to Young Adulthood

The figure depicts the trajectory of body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) between adolescence and young adulthood (solid lines), as determined on the basis of repeated measurements of BMI among 37,674 men. It also shows the 50th percentile curves for the group of men in whom coronary heart disease (CHD) or diabetes eventually developed (dashed lines). BMI progression lines increased roughly in parallel during the transition from adolescence to young adulthood. The mean annual rate of rise in BMI between the ages of 17 and 30 years was 0.3 BMI units per year, corresponding to a total of approximately 15 kg, or 4 BMI units.

Figure 2. Hazard Ratios for the Risk of Diabetes and Coronary Heart Disease among Apparently Healthy Young Adults, According to BMI in Adolescence and in Adulthood

The joint association of body-mass index (BMI) at 17 years of age (adolescence) and 30 years of age (adulthood) is shown for the incidence of diabetes (Panel A) and the incidence of angiography-proven coronary heart disease (CHD) (Panel B), as calculated with the use of multivariate Cox proportional-hazards models. The gray columns denote significantly elevated hazard ratios as compared with those in the lowest BMI quintile in both adolescence and adulthood (reference group). When BMI was analyzed as a continuous variable with the use of a Cox regression model adjusted for age, triglyceride level, presence or absence of a family history of diabetes, and fasting glucose level, only BMI in adulthood was significantly associated with the risk of diabetes (β = 1.115, P = 0.003; P = 0.89 for interaction with BMI in adolescence). In contrast, in a regression model adjusted for age, triglyceride level, smoking status, presence or absence of a family history of CHD, and levels of high-density lipoprotein cholesterol and low-density lipoprotein cholesterol, BMI in both adolescence and adulthood was significantly and independently associated with the risk of CHD (BMI in adolescence, β = 1.355, P=0.004; BMI in adulthood, β = 1.207, P = 0.03; P < 0.05 for interaction).