Risk of myocardial infarction and heart failure among metabolically healthy but obese individuals: HUNT (Nord-Trøndelag Health Study), Norway.

OBJECTIVES: This study sought to investigate whether obesity in the absence of metabolic abnormalities might be a relatively benign condition in relation to acute myocardial infarction (AMI) and heart failure (HF).

BACKGROUND: The results of previous studies are conflicting for AMI and largely unknown for HF, and the role of the duration of obesity has not been investigated.

METHODS: In a population-based prospective cohort study, a total of 61,299 men and women free of cardiovascular disease were classified according to body mass index (BMI) and metabolic status at baseline. BMI also was measured 10 and 30 years before baseline for 27,196 participants.

RESULTS: During 12 years of follow-up, 2,547 participants had a first AMI, and 1,201 participants had a first HF. Compared with being normal weight (BMI <25 kg/m(2)) and metabolically healthy, the multivariable-adjusted hazard ratio (HR) for AMI was 1.1 (95% confidence interval [CI]: 0.9 to 1.4) among obese (BMI ≥30 kg/m(2)) and metabolically healthy participants and 2.0 (95% CI: 1.7 to 2.3) among obese and metabolically unhealthy participants. We found similar results for severe (BMI ≥35 kg/m(2)), long-lasting (>30 years), and abdominal obesity stratified for metabolic status. For HF, the HRs associated with obesity were 1.7 (95% CI: 1.3 to 2.3) and 1.7 (95% CI: 1.4 to 2.2) for metabolically healthy and unhealthy participants, respectively. Severe and long-lasting obesity were particularly harmful in relation to HF, regardless of metabolic status.

CONCLUSIONS: In relation to AMI, obesity without metabolic abnormalities did not confer substantial excess risk, not even for severe or long-lasting obesity. For HF, even metabolically healthy obesity was associated with increased risk, particularly for long-lasting or severe obesity.