Interaction of Physical Activity and Body Mass Index on Mortality in Coronary Heart Disease: Data from the Nord-Trøndelag Health Study

Objective The role of physical activity in the relationship between body mass index (BMI) and survival in coronary heart disease is unclear. Our aim was to examine the isolated and combined associations among BMI, physical activity, and mortality in subjects with coronary heart disease. Methods A total of 6493 participants (34.4% were women) with coronary heart disease from the Nord-Trøndelag Health Study, with examinations in 1986, 1996, and 2007, were followed to the end of 2014. We calculated hazard ratios (HRs) for all-cause and cardiovascular disease mortality, estimated using Cox proportionate hazard regression adjusted for age, smoking, diabetes, hypertension, self-reported health status, and alcohol. Results A total of 3818 patients died (62.1% of cardiovascular disease) during 30 (median 12.5) years of follow-up. Compared with a BMI of 18.5 to 22.4 kg/m², BMI categories of 25.0 to 27.4 kg/m², 27.5 to 29.9 kg/m², and 30.0 to 34.9 kg/m² had reduced all-cause mortality risk: HR, 0.80; 95% confidence interval (CI), 0.72-0.90; HR, 0.80; 95% CI, 0.71-0.90; HR, 0.83; 95% CI, 0.74-0.95, respectively. The BMI categories 25.0 to 27.4 kg/m² and 27.5 to 29.9 kg/m² had reduced cardiovascular disease mortality risk: HR, 0.81; 95% CI, 0.70-0.94; HR, 0.83; 95% CI, 0.71-0.96, respectively. Compared with physically inactive, all levels of physical activity were associated with reduced all-cause and cardiovascular disease mortality risk. In physically inactive, all BMI categories >25.0 kg/m² had reduced all-cause mortality risk (HRs across BMI categories: 0.77, 0.79, 0.79, 0.74), whereas in subjects who were following or exceeding the recommended level of physical activity, BMI was not associated with survival. Conclusions Overweight and obese subjects with coronary heart disease had reduced all-cause and cardiovascular disease mortality, but such an obesity paradox was seen only in participants who did not adhere to current recommendations of physical activity.