Background: Although cardiovascular disease (CVD) is the biggest global cause of death, CVD mortality is falling in developed countries. There is concern that this trend may be offset by increasing levels of obesity.
Design: We used the Systematic Coronary Risk Evaluation (SCORE) data set to examine relationships between body mass index (BMI), conventional risk factors and CVD mortality.
Methods: The SCORE data set comprises data from 12 European cohort studies. The relationship between BMI and CVD mortality was examined in each BMI category using univariable and multivariable (Cox) analyses. The SCORE population was also divided into gender and age strata: under 40, 40-49, 50-59, and over 60. The rate of CVD mortality in each BMI category was calculated within each gender and age stratum. Relationships between BMI and other CVD risk factors were also examined.
Results: There was a strong, graded but J-shaped univariable relationship between BMI and CVD mortality in both genders. Each 5-unit increase in BMI was associated with an increase in CVD mortality of 34% in men and 29% in women. The hazard ratios remained significant when adjusted for age, self-reported smoking status, total cholesterol, and systolic blood pressure (SBP). On additional adjustment for diabetes and high-density lipoprotein cholesterol (HDL), the association between BMI and CVD mortality did not persist. In all age groups except those over 60 there were significant relationships between increased BMI and CVD mortality. In the over-60 age group the only significant relationships with mortality were in underweight and severely overweight women and mildly obese men. After adjustment for age, each 1-unit increase in BMI was associated with a 1.14 mmHg increase in SBP, 0.055 mmol/l increase in total cholesterol, and a 0.024 mmol/l decrease in HDL in men. Figures were slightly lower in women.
Conclusions: Overall, overweight and obesity relate to CVD mortality in a strong and graded manner. The effects are greater in women and markedly so in younger persons. It is likely that a substantial part of the BMI-associated risk of CVD mortality is mediated through other known CVD risk factors. This increases the public health importance of BMI as both a simple indicator and mediator of CVD risk.