Aging
Assessing the Causal Impact of Leisure-Time Physical Activity and Screen Time on Lifespan: A Mendelian Randomization Study Zhu Liduzi Jiesisibieke* Zhu Liduzi Jiesisibieke Zhu Liduzi Jiesisibieke C Mary Schooling
Objectives. Observational studies have consistently shown physical activity associated with lower mortality. However, randomized controlled trials to confirm the value of physical activity for lifespan in the general population are infeasible. To address this gap, we conducted a Mendelian Randomization (MR) study, using the largest available suitable studies and control outcomes.
Method. We conducted a two-sample MR study. We used single nucleotide polymorphisms strongly (p < 5× 10−8) and independently (r2<0.001) predicting more than 30 minutes per week of moderate to vigorous intensity physical activity during leisure time and conversely predicting leisure screen time to obtain inverse-variance weighted estimates. We adjusted for household income using multivariable MR. We used waist circumference and whole-body fat mass as control outcomes. Sensitivity analyses included the weighted median, MR-Egger, MR-PRESSO and MRlap.
Results. Physical activity was associated with longer lifespan, which remained evident after adjusting for household income (1.71 years, 95% CI: 0.43 to 2.99 years) with similar estimates for men (1.79 years, 95% confidence interval (CI) 0.09 to 3.5 years) and overall. Conversely, leisure screen time was associated with shorter lifespan, which was less evident after adjusting for household income. As expected, physical activity reduced and screen time increased waist circumference and whole-body fat mass, which remained evident for whole-body fat mass after adjusting for household income.
Conclusions. Physical activity may extend lifespan, while the role of leisure screen time is less clear. Questions remain about the optimal type, duration, intensity, and frequency of physical activity.