Association between the metabolically healthy obese phenotype and the risk of myocardial infarction: results from the Kailuan study

Objective This study aimed to determine if the metabolically healthy obese (MHO) is associated with an increased risk of myocardial infarction (MI) in Chinese population. Design The Kailuan study is a community-based prospective cohort study. Methods BMI and metabolic syndrome (MetS) were assessed in 91 866 participants without a history of MI or stroke. Participants were categorised into six mutually exclusive groups according to the BMI-MetS status: normal weight (BMI: ≤ 18.5to < 24.0 kg/m 2 ) without MetS (MH-NW), normal weight with MetS (MUH-NW), overweight (BMI: ≤ 24.0to < 28.0 kg/m 2 ) without MetS (MH-OW), overweight with MetS (MUH-OW), obese (BMI ≥ 28.0 kg/m 2 ) without MetS (MHO) and obese with MetS (MUO). The hazard ratio (HR) with 95% CI was calculated for the incidence of MI using a multivariable Cox model. Results A total of 6745 (7.34%) individuals were classified as MHO. During a median 8-year follow-up, 1167 (1.27%) participants developed MI. The MHO group had an increased risk of MI (HR: 1.76, 95% CI: 1.37–2.25) in comparison with the MH-NW group after adjusting for potential confounding variables. After a similar adjustment, the risk of MI was significantly elevated in the MUH-NW (HR: 1.62, 95% CI: 1.28–2.05), MUH-OW (HR: 1.98, 95% CI: 1.67–2.35) and MUO group (HR: 2.06, 95% CI: 1.70–2.49). Conclusions MHO subjects showed a substantially higher risk of MI in comparison with MH-NW subjects. That said, even without measurable metabolic abnormalities, obesity was associated with a higher risk of MI.