Physical activity, cardiorespiratory fitness and risk of cutaneous malignant melanoma: Systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational studies (cohort and case-control studies).
PubMed 30379884 · doi:10.1371/journal.pone.0206087
What was done
A PRISMA-compliant systematic review and meta-analysis evaluated the association of physical activity and cardiorespiratory fitness with cutaneous malignant melanoma incidence. The review identified 3 cohort studies (12,605 cases) and 5 case-control studies (1,295 cases) assessing physical activity, alongside 1 cohort study (49 cases) assessing cardiorespiratory fitness.
What was found
Cohort studies showed a statistically significant positive association between high versus low physical activity and melanoma risk (RR = 1.27, 95% CI: 1.16–1.40). Conversely, case-control studies showed a statistically non-significant inverse association (RR = 0.85, 95% CI: 0.63–1.14), with a significant difference between study designs (P-difference = 0.02). The single cohort study on cardiorespiratory fitness found a positive, statistically non-significant risk increase (RR = 2.19, 95% CI: 0.99–4.96).
Why it matters
This meta-analysis quantifies the apparent paradox where higher physical activity correlates with increased melanoma risk, highlighting that outdoor exposure without adequate UV control can bias observational associations between exercise and skin cancer.
Limits
The analysis relies entirely on observational studies with divergent results between cohort and case-control designs. Cardiorespiratory fitness was evaluated in only one small cohort (49 cases). Most critically, cohort studies had inadequate adjustment for ultraviolet radiation-related risk factors, leaving substantial potential for residual confounding.
Cited by
- supports Individuals who regularly exercise have higher rates of skin cancer than non-exercisers due to increased sun exposure.