Effect of regular exercise on stroke prevention: an instrumental variables approach

In South Korea, around 105,000 individuals experience strokes annually, with over 26,000 deaths and the incidence rate is keep rising due to the aging population. Physical inactivity is a major global health issue, and regular exercise is known to prevent many diseases, including stroke. Yet, previous observational studies may be biased due to unobserved factors influencing exercise and stroke occurrence. Therefore, this study aims to examine an impact of regular physical activity on stroke prevention among South Korean adults using instrumental variable approach in order to avoid problems with reverse causality and other unobserved confounding factors.

Data were obtained from the 2014 and 2016 Korean Community Health Surveys of 416,032 Korean adults. Regular exercise was the main independent variable and proximity to exercise facilities is used as an instrument. The dependent variable, presence of stroke, was defined by a doctor's diagnosis. Probit regression analyses were performed to examine the associations between the independent variable and both dependent variable and an instrument. Causal effect of regular exercise on stroke prevention were estimated with the bivariate probit regressions using proximity to exercise facilities as an instrument for regular exercise.

Consistent with prior knowledge, proximity to exercise facilities positively influenced regular exercise. The results from both multivariable probit and bivariate probit models indicate that engaging in regular exercise has a strong negative effect on the incidence of stroke. The estimated effects of regular physical activity on stroke prevention range from -0.174 percentage points (ATE) to -0.154 percentage points (ATT) in the bivariate probit model.

This study makes an important contribution by providing IV estimates on the effects of conducting regular exercise on stroke prevention based on a representative sample of South Korean adults. My findings suggest that conducting regular exercise reduces the risk of stroke even after accounting for the potential reverse causality and unobserved related factors.