Associations of overweight and obesity with the risk of cardiovascular disease according to metabolic risk factors among middle-aged Japanese workers: The Aichi Workers' cohort study.

BACKGROUND: The association between obesity and cardiovascular disease (CVD) remains unclear, particularly for those with established CVD risk factors. We analyzed follow-up data from the Aichi Workers' Cohort Study. We studied the association between the degree of obesity and risk of CVD and its subtypes specifically among individuals with hypertension, hyper-low-density lipoprotein (LDL)-cholesterolemia, or diabetes.

METHODS: Pooled data of 8972 adults (7076 men and 1896 women) who were recruited between 2002 and 2008 were used in the current analysis. We used multivariable Cox proportional hazard model to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations between the degree of obesity assessed with body mass index (BMI) and the risk of CVD and its subtypes, i.e., coronary heart disease (CHD) and stroke.

RESULTS: During a median of 12 years, there were 197 CVDs (80 CHDs and 117 strokes). BMI ≥ 27.5 compared to 21.0-22.9 kg/m2 was positively and significantly associated with the risks of CVD, CHD, and total stroke. Hypertension, hyper-LDL-cholesterolemia, and diabetes mediated 15.9%, 5.8%, and 8.7% of obesity-CVD associations, respectively, and 28.3% by their combination. In the stratified analyses by the presence of risk factors, BMI ≥ 25.0 (overweight/obesity) compared to BMI < 25 kg/m2 was associated with a higher risk of CVD in those with and without hypertension, but only with hyper-LDL-cholesterolemia, and without diabetes.

CONCLUSIONS: Overweight/obesity was associated with the risk of CVD and its subtypes. About 30% of the risk was explained by hypertension, hyper-LDL-cholesterolemia, and diabetes, of which hypertension accounted for approximately the half of the explained risk. However, overweight/obesity increased the risk of CVD even in those without hypertension. These findings highlight the importance of controlling and preventing overweight/obesity regardless of chronic disease status.