Tailoring physical activity recommendations to reduce cardiovascular mortality: interactions with age, sex and body morphology

Background: This prospective cohort analysis investigated how age, sex, and body morphology modify associations of physical activity (PA) intensity, duration, and volume with cardiovascular disease (CVD) mortality. Methods: We analysed wrist-worn accelerometer data from 8,661 adults (51.9% women) in the National Health and Nutrition Examination Survey. The outcome was CVD mortality. PA intensity and volume were quantified using the intensity gradient and average acceleration, respectively. Survey-weighted Cox proportional hazards models were used to estimate associations, including interaction terms with age, sex, or body morphology (waist-to-height ratio as indicator of adiposity). Results: Median (interquartile range) follow-up was 81 (69, 94) months. All hazard ratios (HR) compare 50th with 25th percentile. Beneficial associations between CVD mortality and PA were stronger in younger than older adults for intensity (e.g., 45-year-olds: HR=0.47, 95%CI:0.29-0.75 vs 75-year-olds: HR=0.75, 95%CI:0.54-1.06), and volume (e.g., HR=0.18, 95%CI:0.07-0.71 vs 0.29, 95%CI:0.16-0.51). In women, intensity-related association were stronger than in men (HR=0.45, 95%CI:0.31-0.65 vs HR=0.79, 95%CI:0.50-1.24). Volume-related associations were stronger in men (HR=0.37, 95%CI:0.22-0.60 vs HR=0.24, 95%CI:0.11-0.51), though with earlier plateauing and greater uncertainty. Associations were observed across waist-to-height ratio levels but attenuated at higher values (intensity: waist-to-height ratio 0.5, HR=0.45, 95%CI:0.29-0.69 vs 0.6, HR=0.69, 95%CI:0.49-0.97; volume: 0.5, HR=0.07, 95%CI:0.03-0.17 vs 0.6, HR=0.28, 95%CI:0.17-0.45). Conclusion: Older adults and men may benefit more from increasing PA volume than intensity, whereas younger adults and women may benefit more from higher-intensity PA. Although benefits were observed across adiposity levels, associations were attenuated as adiposity increased, suggesting stronger benefits in individuals with low-to-moderate adiposity.