Sleep and cancer: Synthesis of experimental data and meta-analyses of cancer incidence among some 1,500,000 study individuals in 13 countries.
Level 3 - non-randomized controlled study
Meta-analysis of observational epidemiological studies
PubMed 27003385 · doi:10.3109/07420528.2016.1149486
What was done
The authors synthesized experimental data and conducted meta-analyses of observational epidemiological studies evaluating associations between sleep parameters (duration, napping, or "poor sleep") and cancer incidence across approximately 1,500,000 individuals from 13 countries.
What was found
Combined adjusted relative risks (meta-RRs) for cancer incidence were: - Female breast cancer: 1.01 (95% CI: 0.97-1.06), based on heterogeneous data. - Colorectal cancer (men and women): 1.08 (95% CI: 1.03-1.13), based on homogeneous data. - Lung cancer (men and women): 1.11 (95% CI: 1.00-1.22). - Prostate cancer: 1.05 (95% CI: 0.83-1.33).
Why it matters
Despite biological plausibility connecting circadian disruption to carcinogenesis, epidemiological data show largely inconclusive associations overall, with only a modest, statistically significant increase detected for colorectal cancer.
Limits
The underlying evidence is observational, prone to residual confounding, and limited by likely misclassification of sleep exposures over time. Breast cancer data displayed notable heterogeneity, and the abstract does not report the total number of included studies or specific exposure definitions.
Cited by
- contradicts Short sleep duration of six hours or less is epidemiologically linked to an increased risk of bowel, prostate, and breast cancer.