Importance: Overweight and obesity likely cause myocardial infarction (MI) and ischemic heart disease (IHD); however, whether coexisting metabolic syndrome is a necessary condition is unknown.
Objective: To test the hypothesis that overweight and obesity with and without metabolic syndrome are associated with increased risk of MI and IHD.
Design, setting, and participants: We examined 71,527 individuals from the Copenhagen General Population Study and categorized them according to body mass index (BMI) as normal weight, overweight, or obese and according to absence or presence of metabolic syndrome.
Main outcomes and measures: Hazard ratios for incident MI and IHD according to combinations of BMI category and absence or presence of metabolic syndrome.
Results: During a median of 3.6 years' follow-up, we recorded 634 incident MI and 1781 incident IHD events. For MI, multivariable adjusted hazard ratios vs normal weight individuals without metabolic syndrome were 1.26 (95% CI, 1.00-1.61) in overweight and 1.88 (95% CI, 1.34-2.63) in obese individuals without metabolic syndrome and 1.39 (95% CI, 0.96-2.02) in normal weight, 1.70 (95% CI, 1.35-2.15) in overweight, and 2.33 (95% CI, 1.81-3.00) in obese individuals with metabolic syndrome. For IHD, results were similar but attenuated. Normal weight vs overweight vs obesity and presence vs absence of metabolic syndrome did not interact on risk of MI or IHD (P = .90 and P = .44). Among individuals both with and without metabolic syndrome there were increasing cumulative incidences of MI and IHD from normal weight through overweight to obese individuals (log-rank trend P = .006 to P < .001). Although the multivariable adjusted hazard ratio for MI in individuals with vs without metabolic syndrome was 1.54 (95% CI, 1.32-1.81) across all BMI categories, addition of metabolic syndrome to a multivariable model including BMI and other clinical characteristics improved the Harell C-statistic only slightly for risk of MI (comparison P = .03) but not for IHD (P = .41).
Conclusions and relevance: These findings suggest that overweight and obesity are risk factors for MI and IHD regardless of the presence or absence of metabolic syndrome and that metabolic syndrome is no more valuable than BMI in identifying individuals at risk.