Physical activity and risk of thyroid cancer: a systematic review and meta-analysis of prospective cohort studies.

BACKGROUND

The preventive effect of physical activity on the risk of thyroid cancer remains inconsistent and unclear. We investigated the association between physical activity and the risk of thyroid cancer using a meta-analysis of prospective cohort studies.

METHODS

A systematic search of PubMed and EMBASE was conducted from inception till December 20, 2024. A pooled relative risk (RR) with its 95% confidence interval (CI) was calculated using an adjusted RR with its 95% CI from each study.

RESULTS

A total of nine prospective cohort studies (N = 2 764 014 adults; incident thyroid cancer cases, 15 166) were included in the final analysis. In the meta-analysis of all the studies, highest physical activity was not significantly associated with the risk of thyroid cancer (RR, 0.91; 95% CI 0.76-1.09; I2 = 56.5%), compared with lowest physical activity. Physical activity was statistically significantly associated with a decreased risk of thyroid cancer in the studies conducted in Asia (RR, 0.75; 95% CI 0.64-0.88; I2 = 4.2%), but not in either Europe or North America. Also, physical activity was statistically significantly associated with a decreased risk of thyroid cancer in the studies published after 2015 (RR, 0.78; 95% CI 0.65-0.93; I2 = 22.1) and the high-quality studies (RR, 0.81; 95% CI 0.70-0.94; I2 = 5.2).

CONCLUSIONS

Physical activity decreased the risk of thyroid cancer in the studies conducted in Asia, published after 2015, and rated as having high methodological quality. Further high-quality prospective cohort studies are warranted to confirm our findings.