Post-MI mortality is significantly lower in people with higher than normal BMI, but much higher in people with lower than normal BMI

The risk of post-myocardial infarction (post-MI) mortality was found to be significantly lower in overweight or obese people, but significantly higher in people with a body mass index (BMI) below the ideal beach. That was the conclusion of a systematic review and meta-analysis by an international team led by researchers from the University of Aberdeen, Scotland, UK.

Body mass index (BMI) is a measure of nutritional status in adults and defined as a person’s weight in kilograms divided by the square of the person’s height in meters (kg/m2). Based on BMI, individuals are considered normal weight when their BMI is 18.5 and 24.9. According to the World Health Organization, individuals with a BMI > 25 are classified as overweight and obese when their BMI is equal to or > 30). According to the American Heart Association, the presence of obesity leads to the development of cardiovascular disease and mortality, independent of other cardiovascular risk factors. However, there is growing evidence that patients with a high BMI may have better outcomes if they develop cardiovascular or kidney disease, the so-called ‘obesity paradox’. Despite this, meta-analyses support a J-shaped relationship between mortality and BMI in patients with coronary heart disease, i.e. the risk is highest for those who are underweight and overweight and lowest for those with a normal BMI.

Nevertheless, whether this same J-shaped relationship holds for post-MI mortality is unknown and has been the subject of the present meta-analysis. The researchers searched for studies in adults with a prior myocardial infarction where BMI had been measured and that reported outcomes such as all-cause mortality, recurrence of an adverse cardiovascular event, or readmission to the hospital. ‘hospital. Relative risks (HR) were used to assess mortality risk and normal BMI (18.5 to 24.9) was used as the reference range for comparison.

Post-MI Mortality and Body Mass Index

A total of 27 articles with 308,430 participants and with follow-up periods ranging from 6 months to 17 years were included in the analysis.

Among individuals classified as overweight (BMI 25 – 29.9) compared to those with a normal BMI and based on 8 studies, there is a 15% lower risk of post-MI mortality (Hazard ratio, HR = 0 .85, 95% CI 0.76 – 0.94, p=0.002). In 14 studies looking at odds ratios (ORs) rather than hazard ratios, there was also a reduced risk of mortality (OR = 0.72, 95% CI 0.64 – 0.81, p

In obese patients (BMI > 30), the relative risk was 0.86 (95% CI 0.81 – 0.91, p

In contrast, among people with a BMI

There was no significant effect when comparing the risk of hospital readmission for overweight, obese, and underweight people.

The authors concluded that people with lower than normal BMIs have a significantly higher risk of post-MI mortality. They called for future studies to examine the prognostic utility of other markers of nutritional status in myocardial infarction to better identify people at higher risk for poor clinical outcomes.

Quote
By Paola L et al. Body mass index and mortality, recurrence and readmission after myocardial infarction: systematic review and meta-analysis J Clin Med 2022