Association between BMI and cause-specific long-term mortality in acute myocardial infarction patients.

Background To investigate the association between body mass index (BMI) at acute myocardial infarction (AMI) and all-cause as well as cause-specific long-term mortality. Methods The analysis was based on 10,651 hospitalized AMI patients (age 25-84 years) recorded by the population-based Myocardial Infarction Registry Augsburg between 2000 and 2017. The median follow-up time was 6.7 years [IQR: 3.5-10.0)]. Cause-specific mortality was obtained by evaluating the death certificates. In multivariable-adjusted COX regression models using cubic splines for the variable BMI, the association between BMI and cause-specific mortality (all-cause, cardiovascular, ischemic heart diseases, cancer) was investigated. Additionally, a subgroup analysis in three age groups was performed for all-cause mortality. Results Overall, there was a statistically significant U-shaped association between BMI at AMI and long-term mortality with the lowest hazard ratios (HR) found for BMI values between 25 and 30 kg/m². For cancer mortality, higher BMI values > 30 kg/m² were not associated with higher mortality. In patients aged <60 years, there was a significant association between BMI values > 35 kg/m² and increased all-cause mortality; this association was missing in 60 to 84 years old patients. For all groups and for each specific cause of mortality, lower BMI (< 25kg/m²) values were significantly associated with higher mortality. Conclusions Overall, a lower BMI – and also a high BMI in patients younger than 60 years - seem to be a risk factors for increased all-cause mortality after AMI. A BMI in a mid-range between 25 and 30 kg/m² is favorable in terms of long-term survival after AMI. What is Known? Obesity is considered a major risk factor for cardiovascular diseases and coronary artery disease. Nonetheless, the results of prior studies indicated lower mortality for overweight and obese individuals after acute myocardial infarction (AMI); a phenomenon often called ‘obesity paradox’. What the Study Adds This study analyzed the association between body mass index (BMI) and cause-specific long-term mortality after AMI in a population-based cohort of 10.000 AMI patients recorded by the Myocardial Infarction Registry Augsburg. The obesity paradox was partially confirmed, as we found a U-shaped association between BMI and long-term mortality with the lowest risk of mortality in overweight individuals. For cancer mortality and in elderly, obesity (BMI > 30 kg/m²) was not associated with mortality. Lower BMI < 25 kg/m² went along with significantly higher mortality in all age groups and for all causes of death (all-cause, cardiovascular, ischemic heart disease, cancer)