Association of the Obesity Paradox With Objective Physical Activity in Patients at High Risk of Sudden Cardiac Death

To investigate the obesity paradox and its interrelationship with objective physical activity (PA) in patients at high risk of sudden cardiac death.

A total of 782 patients with implantable cardioverter-defibrillators/cardiac resynchronization therapy defibrillators in the Study of Home Monitoring System Safety and Efficacy in Cardiac Implantable Electronic Device-Implantable Patients registry were retrospectively analyzed and grouped by body mass index (BMI) (kg/m2): normal weight (18.5 ≤ BMI < 25) and overweight or class I obesity (25 ≤ BMI < 35). PA was measured with home monitoring and categorized into 4 groups (Q1-Q4) by the baseline quartiles. The main endpoint was all-cause mortality.

During a mean follow-up period of 59.9 ± 21.9 months, 182 all-cause mortality events occurred. Mortality tended to be lower in overweight and obesity patients (18.9% vs 25.1%, P = 0.061) and decreased by PA quartiles (44.1% vs 22.6% vs 15.3% vs 11.2%, Q1-Q4, P < 0.001). Multivariate Cox analysis indicated BMI (hazard ratio, 0.918; 95% confidence interval, 0.866-0.974; P = 0.004) and PA (0.436, 0.301-0.631, Q2 vs Q1; 0.280, 0.181-0.431, Q3 vs Q1; 0.257, 0.158-0.419, Q4 vs Q1; P < 0.001 for all) were associated with reduced risk. The obesity paradox was significant in the total cohort (log rank P = 0.049) and low PA group (log rank P = 0.010), but disappeared in the high PA group (log rank P = 0.692). Dose-response curves showed a significant reduction in risk with low-moderate PA, and the pattern varied between different BMI groups.

The obesity paradox only persisted in physically inactive patients. PA might be related to the development of the obesity paradox.