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

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

Methods: 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.

Results: 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.

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