Sex differences in the relationship between body mass index and outcome in myocardial infarction.

BACKGROUND: The data on sex-related differences regarding the body mass index (BMI) in patients with myocardial infarction (MI) are rare and inconclusive. We aimed to assess sex differences in the relationship between BMI and 30-day mortality in men and women with MI. METHODS: A single-center retrospective study of 6453 patients with MI who underwent PCI was performed. Patients were divided into five BMI categories and these were compared. The relationship between BMI and 30-day mortality was assessed in men and women. RESULTS: An L-shaped relationship between BMI and mortality was observed in men (p=0.003) with the highest mortality rate (9.4%) in normal weight patients and the lowest in patients with obesity grade I (5.3%). In women, similar mortality was found in all BMI categories (p=0.42). After adjustment for potential confounders, the negative association between BMI category and 30-day mortality was found in men, but not in women (p=0.033 and p=0.13, respectively). Overweight men had a 33% lower risk of death within 30 days compared to normal weight patients (OR 0.67,95%CI 0.46-0.96;p=0.03). Other BMI categories in men had a similar mortality risk to the normal weight category. CONCLUSIONS: Our results suggest that the relationship between BMI and outcome in patients with MI is different in men and women. We found an L-shaped relationship between BMI and 30-day mortality in men, but no relationship was observed in women. The obesity paradox was not found in women. Sex itself could not explain this differential relationship, and the underlying cause is likely multifactorial.