Objective To analyze the causal relationship between physical activity of varying intensities and the risk of hypertension using a Mendelian randomization (MR) analysis.

Methods Physical activity was categorized into six categories based on intensity and type: vigorous exercise (＞6.0 METs), heavy physical labor (3.0–6.0 METs), moderate-intensity recreational exercise (3.0–6.0 METs), walking (＜3.0 METs), light physical labor (＜3.0 METs), no physical activity (＜1.5 METs). Single nucleotide polymorphisms (SNPs) strongly associated with these activity types were selected as instrumental variables from the Integrative Epidemiology Unit openGWAS (IEU OpenGWAS) database. The causal relationships between physical activity of different types and hypertension risk were assessed using inverse variance weighted (IVW), MR-Egger regression, weighted median, simple mode, and weighted mode methods. Sensitivity analyses were conducted to evaluate potential horizontal pleiotropy and heterogeneity among the SNPs.

Results The MR analysis revealed significant negative causal associations between heavy physical labor (compared with non-heavy physical labor, OR=0.296, 95%CI: 0.136–0.641, P=0.002) and moderate-intensity recreational exercise (compared with non-moderate-intensity recreational exercise, OR=0.135, 95%CI: 0.057–0.313, P＜0.001) with hypertension. Walking (compared with non-walking, OR=0.336, 95%CI: 0.113–0.994, P=0.048) showed a negative association with hypertension, while this relationship became suggestive evidence after Bonferroni correction. No significant causal relationships were observed for vigorous exercise (compared with non-vigorous exercise, OR=0.168, 95%CI: 0.081–3.459, P=0.247), light physical labor (compared with non-light physical labor, OR=0.349, 95%CI: 0.111–1.099, P=0.072), or no physical activity (compared with physical activity, OR=132.874, 95%CI: 0.159–110 526.501, P=0.154) with hypertension.

Conclusions Physical activity of different intensities exhibits potential causal associations with hypertension. Heavy physical labor, moderate-intensity recreational exercise, and walking may confer protective effects against hypertension.