The association between obesity and acute myocardial infarction is age- and gender-dependent in a Japanese population

Controversies concerning the association between obesity and acute myocardial infarction (AMI) are still ongoing in Japan. We investigated the association between obesity defined by body mass index of 25 kg/m2 or higher and AMI by a case–control study using data from 1199 AMI cases and 4056 apparently healthy controls. The analysis was performed in age- and sex-matched samples of 621 case–control pairs younger than 80 years and in crude samples aged 40–79 years divided into 10-year age groups. Prevalence of obesity, diabetes, current smoking, hypertension, and hypercholesterolemia were compared between cases and controls, and a multivariable odds ratio (OR) of AMI was calculated for each risk factor in various age groups. The OR (95 % confidence interval (CI)) of AMI for obesity was 1.63 (1.23–2.17), P = 0.0008 in men younger than 80 years; 2.65 (1.41–5.00), P = 0.0025 in women younger than 80 years; 2.23 (1.46–3.41), P = 0.0002 in men aged 59 years or younger; 1.34 (0.90–2.01), P = 0.1510 in men aged 60–79 years; and 2.98 (1.56–5.71), P = 0.0010 in women aged 60–79 years using paired samples. The OR (95 % CI) of AMI for obesity was 4.92 (2.53–9.58), P < 0.0001 in men aged 40–49 years; 1.54 (1.07–2.21), P = 0.0197 in men aged 50–59 years; 1.07 (0.69–1.66), P = 0.7717 in men aged 60–69 years; 2.24 (1.20–4.20), P = 0.0118 in men aged 70–79 years; 2.48 (1.12–5.48), P = 0.0245 in women aged 60–69 years; and 3.05 (1.46–6.37), P = 0.0029 in women aged 70–79 years using crude samples. The association between obesity and AMI was age- and gender-dependent in a Japanese population.