In a database analysis of 22 studies of COPD patients that compared their body mass index (BMI, a measure of whether body weight is high or low) with mortality rates, some surprising findings were made. As might be expected, patients with a normal BMI had lower mortality compared to underweight COPD patients. But here’s the surprise; overweight or even obese patients also had lower mortality than underweight patients. In other words, among patients with COPD, being overweight or obese had a protective effect against mortality. The researchers did note, however, that the relationship between BMI and mortality across different levels of obesity needed further study. Data from a total of 21,150 patients were analyzed for this research.
So why is weight, or BMI, a determinant of mortality among COPD patients? The paradoxical benefit of a higher BMI is little understood, but researchers have found that a higher BMI is associated with both lower lung volumes and greater lung elastic recoil (ability to compress and force air out of the lungs). The better the lung elastic recoil, the higher the expiratory airflow, or ability to breathe out air. Patients with higher expiratory airflows have a lower risk of COPD exacerbations (“flare-ups”) and death.
Wondering what your BMI is? Watch for next week’s article, “How to Calculate Your Own BMI.”