Sleep Duration and Cancer: Site-Specific and Mixed
Zhao 2013 “suggests a positive association between long sleep duration and colorectal cancer”, Chen 2018 reports long sleep associated with colorectal cancer in categorical but not dose-response analysis, and Li 2022 concludes that abnormal sleep duration “might be linked to several adverse cancer-related outcomes”; long sleep is also associated with cancer mortality (Ma 2016; Wilunda 2022); short sleep with cancer risk in Asian populations in categorical but not dose-response analysis (Chen 2018); and for breast cancer He 2015 reports circadian disruption associated with higher risk and no significant effect for short sleep, Yang 2014 reports light at night associated with higher risk and no significant sleep-duration dose-response, Pagkalidou 2026 reports evening chronotype associated with higher risk, and Zhao 2013 reports long sleep associated with a 21% lower risk of hormone-related cancers such as breast cancer.
What the evidence says
The sources on this entry are meta-analyses, an umbrella review and a pooled cohort analysis of sleep duration, circadian disruption and cancer incidence or mortality; all are observational. On colorectal cancer, Zhao 2013 (meta-analysis, 12 studies, 723,337 participants) reports long sleep associated with a 29% higher risk of colorectal cancer and a 21% lower risk of hormone-related cancers. Chen 2018 (meta-analysis, 65 studies, 1,550,524 participants) reports long sleep associated with a 21% higher colorectal cancer risk and short sleep with a 36% higher cancer risk in Asian populations in categorical analysis, findings that were not consistent in its dose-response meta-analysis, with no significant effect on overall cancer risk. Li 2022 (umbrella review of 6 systematic reviews) reports long sleep associated with a 21% higher colorectal cancer risk, 9% higher all-cancer mortality and 65% higher lung cancer mortality, and short sleep with 21% higher lung cancer mortality, concluding that abnormal sleep duration might be linked to several adverse cancer-related outcomes. On cancer mortality, Ma 2016 (meta-analysis, 11 prospective studies) reports long but not short sleep associated with significantly higher total cancer mortality (RR 1.11), and Wilunda 2022 (pooled analysis of 6 Japanese cohorts, 271,694 participants) reports sleep of 10 hours or more associated with higher cancer incidence and mortality in women and cancer mortality in men. On breast cancer, Yang 2014 (meta-analysis, 16 studies) reports high artificial light at night associated with higher breast cancer risk (RR 1.17) and no significant sleep-duration dose-response. He 2015 (meta-analysis, 28 studies, 1,728,237 participants) reports circadian disruption associated with a 14% higher breast cancer risk, each 10-year increment of shift work with a 16% higher risk and no significant effect for short sleep, and concludes that a dose-response relationship remains uncertain. Pagkalidou 2026 (meta-analysis, 62 studies) reports evening chronotype associated with higher breast and epithelial ovarian cancer risk, with the insomnia association lost in properly adjusted studies, and concludes that the findings support a role for circadian disruption in carcinogenesis. These are observational associations; nothing here diagnoses, predicts or treats cancer in any individual.
- Myth: Sleeping too little causes cancer. Actually: the review reports that the short-sleep signal appears mainly in Asian populations, that breast-cancer analyses conflict, and that the clearer signal is circadian disruption rather than duration.
- Does not diagnose, treat, or cure any disease or injury
- Not a substitute for individualized medical or physical-therapy advice
- Results vary between individuals; no guaranteed outcome
- Agreement
- Direction recorded for 0 of 8 sources; not yet recorded for the rest.
- The claim's outcome
- Outcome not yet recorded
- Certainty
- No source states a certainty rating.
- How the sources were read
- Some sources are based on abstracts, not full texts.
What each source measured and concluded (8)
- What it measured
- Cancer risk.
- How it measured it
- Hazard ratios (HRs) and relative risks (RRs) from cohort studies.
- How it was read
- read in full text
- What the review says it includes
- Meta-analysis of 12 studies
- Studies and participants, as stated
- N=723,337 participants across 12 studies
- What it measured
- Breast cancer risk in women.
- How it measured it
- Relative risks (RRs) and corresponding 95% confidence intervals (CIs) from observational studies.
- How it was read
- read in full text
- What the review says it includes
- Meta-analysis of 28 observational studies
- Studies and participants, as stated
- N=1,728,237 participants across 28 studies
- Heterogeneity, as stated
- Significant heterogeneity due to inconsistent exposure definitions
- What it measured
- Cancer risk.
- How it measured it
- Odds ratios (ORs) and confidence intervals (CIs) from cohort and case-control studies using self-report questionnaires or interviews.
- How it was read
- read in full text
- What the review says it includes
- Meta-analysis of 65 studies from 25 articles
- Studies and participants, as stated
- N=1,550,524 participants across 65 studies
- Heterogeneity, as stated
- Combination of different study designs (cohort and case-control studies) introduces heterogeneity.
- What it measured
- Cancer risk and mortality.
- How it measured it
- Questionnaires or interviews (self-report).
- How it was read
- read in full text
- What the review says it includes
- Umbrella review of 6 systematic reviews and meta-analyses
- Studies and participants, as stated
- N=428,243 participants across 30 studies
- What it measured
- Cancer incidence and mortality by sleep duration
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Pooled analysis of population-based cohorts (with random-effects meta-analysis)
- Studies and participants, as stated
- N=6 cohorts, 271,694 participants (40,751 incident cancers, 18,323 cancer deaths)
- What it measured
- Total cancer mortality by sleep duration
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Meta-analysis of prospective studies
- Studies and participants, as stated
- N=11 independent prospective studies (17 reports)
- What it measured
- Reproductive cancer risk by sleep traits
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Systematic review and meta-analysis of observational studies
- Studies and participants, as stated
- N=62 studies (45 cohort, 17 case-control) from 55 publications
- What it measured
- Breast cancer risk
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Dose-response analysis/meta-analysis of observational studies
- Studies and participants, as stated
- 16 studies (12 case-control, 4 cohort)
Each source below is shown with its study design and a link to the original study, or, where it is not a completed research paper, with what kind of record it is; those are not counted. This is the audit trail.
Why do some records show a record type instead of a study design?
A study design is shown for a completed, peer-reviewed paper. A registered protocol, a preprint, a conference abstract, a referee report or a book chapter has not been through peer review as a finished paper, so it is labelled for what it is, and it is counted in no source count. Where a record could not be confirmed as a completed paper at all, it says so rather than guessing. They all stay in the list, and their DOI still resolves, because the count of what was screened is part of the audit trail.
- Protocol / registration A registered plan for a review or trial, not its results.
- Preprint Posted by its authors before peer review.
- Conference abstract A conference summary rather than a peer-reviewed paper.
- Peer-review report A referee's report on a paper, not the paper itself.
- Guideline / position stand A recommendation derived from evidence, which is a step further from the data than the evidence itself.
- Book chapter A chapter in a scholarly book rather than a journal paper.
- Type not recorded Our record does not say what kind of publication this is, so it is counted in no source count. That is a gap in our data, not a judgement about the research.
“Abstract only” means the review read that paper’s abstract, not its full text; “screened only” means it was included at re-screening and not extracted. Both stay in the trail with their DOI, because how a source was read is part of the audit.