Muscle-strengthening activities and cancer incidence and mortality: a systematic review and meta-analysis of observational studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational cohort and case-control studies
PubMed 34051796 · doi:10.1186/s12966-021-01142-7
What was done
Researchers performed a systematic review and meta-analysis across PubMed, Embase, Web of Science, and Scopus through March 2020 to evaluate the association between muscle-strengthening activities and cancer incidence and mortality. The review included 12 observational studies (11 cohorts and 1 case-control) with 6 to 25 years of follow-up, comprising 1,297,620 participants, 32,196 cancer cases, and 31,939 cancer deaths. Random-effects models were used to calculate summary hazard ratios (HR) and 95% confidence intervals (CI).
What was found
Muscle-strengthening activities were associated with a 26% reduced incidence of kidney cancer (HR 0.74, 95% CI 0.56 to 0.98; I² = 0%; 2 studies), but showed no significant association with the incidence of 12 other cancer types. For total cancer mortality, engaging in muscle-strengthening activities ≥2 times/week versus <2 times/week was associated with lower mortality (HR 0.81, 95% CI 0.74 to 0.87; I² = 0%; 4 studies), while high versus low activity showed HR 0.87 (95% CI 0.73 to 1.02; I² = 58%; 6 studies). By weekly duration, mortality HRs were 0.91 (95% CI 0.82 to 1.01; I² = 0%; 2 studies) for 1–59 min/week and 0.98 (95% CI 0.89 to 1.07; I² = 0%; 2 studies) for ≥60 min/week compared to none. Combining muscle-strengthening and aerobic activities was associated with a 28% lower total cancer mortality compared to none (HR 0.72, 95% CI 0.53 to 0.98; I² = 85%; 3 studies).
Why it matters
This review provides quantitative evidence that resistance exercise is associated with lower total cancer mortality and reduced kidney cancer incidence, with the greatest benefit observed when muscle-strengthening is performed at least twice weekly or combined with aerobic exercise.
Limits
The evidence is restricted to observational studies with potential residual confounding and exposure misclassification from self-reported physical activity. Several analyses, including kidney cancer incidence and duration-response metrics, relied on only 2 to 3 studies, and substantial statistical heterogeneity (I² = 85%) was present for the combined aerobic and strengthening outcome.
Cited by
- supports Muscular strength training can lower the risk of developing certain types of cancer.