Estimating the effects of body mass index and central obesity on stroke in diabetics and non‐diabetics using targeted maximum likelihood estimation: Atherosclerosis Risk in Communities study

OBJECTIVES: The association of body mass index (BMI) with the risk of cardiovascular disease among diabetic patients is controversial. This study compared the effects of BMI and central obesity on stroke in diabetics and non-diabetics using targeted maximum likelihood estimation. MATERIALS AND METHODS: This analysis included 12 725 adults aged 45-75 years, after excluding prevalence cases and participants with missing data, from the Atherosclerosis Risk in Communities study. Obesity was defined with BMI, waist circumference, waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), body shape index (BSI) and body roundness index (BRI), which categorized all participants as obese and non-obese. Generalized linear models and TMLE (with the tmle package) were used to estimate risk ratio (RR). RESULTS: During 27 years of follow-up, 1078 (8.47%) cases of stroke occurred. After adjustment for demographic, behavioural, biologic and central obesity variables, the effect of BMI decreased in both diabetics and non-diabetics. The effect of BMI in diabetics was more attenuated, in full model, (RR: 1.04 [0.90, 1.20]) rather than non-diabetics (RR: 1.11 [1.00, 1.24]). This attenuation was more related to biologic variables in non-diabetics and central obesity in diabetics. With respect to central obesity, BSI (RR [95% CI]: 1.15 [0.96, 1.38]) and WHR (RR [95% CI]: 1.15 [0.87, 1.52]) had strongest and marginally significant effects for diabetics and BSI (RR [95% CI]: 1.10 [1.02, 1.20]) for non-diabetics. CONCLUSIONS: Among diabetics, BSI and WHR indices were associated with a higher incidence of stroke. Future studies should consider how central obesity affects higher incidence of stroke among diabetics stratified by sex and age groups.