Obesity or smoking: Which factor contributes more to the incidence of myocardial infarction?

Comparing the contributions of smoking and obesity to the risk of myocardial infarction (MI) can help prioritize behavioral modifications. The objective of this study was to determine the relative risk of smoking, obesity and the joint burden on the risk of MI.

This is a retrospective cohort study of data accessed from electronic medical records of the largest health care organization in Israel. The study population included all 738,380 members of Clalit Health Services, with at least one smoking status and one BMI assessment recorded in 2009 or 2010, aged 40-74years, who were MI-free before 2009. Obesity was defined as BMI >30kg/m(2). New and primary MI between January 1 and December 31, 2011 were recorded.

Rates of MI were: 0.18% for non-obese never smokers, 0.25% for obese never smokers, 0.40% for non-obese past smokers, 0.50% for obese past smokers, 0.53% for non-obese current smokers and 0.66% for obese current smokers. Among non-obese individuals, past smokers and current smokers had a greater risk of MI than did never smokers, after adjusting for age, gender and socioeconomic position (OR, 1.45; 95% CI, 1.23-1.70 and OR, 2.35; 95% CI, 2.10-2.63, respectively). The burden of obesity increased the risk of MI for never smokers but the burden of obesity did not elevate the risk of MI when combined with current or past smoking groups, after adjusting for comorbidities.

Past and, more so, current smoking confers greater risk for MI than obesity.