Indoor & outdoor artificial light-at-night (ALAN) & cancer risk: A systematic review & meta-analysis of
Abstract
Indoor & outdoor artificial light-at-night (ALAN) & cancer risk: A systematic review & meta-analysis of multiple cancer sites with a critical appraisal of exposure assessment Palomar-Cros A, Deprato A, Papantoniou K, Straif K, Lacy P, Maidstone R, Adan A, Haldar P, Moitra S, Navarro JF, Durrington H, Moitra S, Kogevinas M, Harding BN. Indoor and outdoor artificial light-at-night (ALAN) and cancer risk: A systematic review and meta-analysis of multiple cancer sites and with a critical appraisal of exposure assessment. Science of The Total Environment, Vol 955, 2024. doi: 10.1016/j.scitotenv.2024.177059. Abstract Exposure to artificial light-at-night (ALAN) has been linked to cancer risk. Few meta-analyses on this topic have reviewed only breast cancer. This study aimed to systematically review and meta-analyze existing studies on ALAN exposure and cancer incidence, thoroughly evaluating exposure assessment quality. We considered observational studies (cohort, case-control, cross-sectional) on ALAN exposure (indoor and outdoor) and cancer incidence, measured by relative risk, hazard ratio, and odds ratio. We searched six databases, two registries, and Google Scholar from inception until April 17, 2024. Quality of studies was assessed using the Joanna Briggs Institute (JBI) critical appraisal tools. Random-effects meta- analysis was used to estimate relative risks (RR) and 95 % confidence intervals (CI) for ALAN exposures. We identified 9835 studies and included 28 for qualitative synthesis with 2,508,807 individuals (15 cohort, 13 case-control). Out of the included studies, 20 studies on breast cancer (731,493 individuals) and 2 studies on prostate cancer (53,254 individuals) were used for quantitative synthesis. Higher levels of outdoor ALAN were associated with breast cancer risk (meta-estimate = 1.12, 95 % CI 1.03–1.23 (I2 = 69 %)). We observed a non-significant positive association between indoor ALAN levels and breast cancer risk (meta-estimate = 1.07, 0.95–1.21, I2 = 60 %), and no differences by menopausal status. The meta-analysis for prostate cancer suggested a non-statistically significant increased risk for higher levels of outdoor ALAN (meta-estimate = 1.43, 0.75–2.72, I2 = 90 %). In the qualitative synthesis, we observed positive associations with non-Hodgkin lymphoma and colorectal, pancreatic and thyroid cancer. We found an association between outdoor ALAN and breast cancer risk. However, most studies relied on satellite-images with a very low resolution (1 to 5 km, from the Defense Meteorological Program [DMSP]) and without information on color of light. Future studies with better exposure assessment should focus on investigating other cancer sites. sciencedirect.com
AI evidence extraction
Main findings
This systematic review and random-effects meta-analysis included 28 observational studies (2,508,807 individuals). Higher outdoor ALAN exposure was associated with increased breast cancer risk (meta-estimate 1.12, 95% CI 1.03–1.23), while indoor ALAN showed a non-significant positive association with breast cancer (1.07, 0.95–1.21) and no differences by menopausal status. For prostate cancer, the meta-analysis suggested a non-statistically significant increased risk with higher outdoor ALAN (1.43, 0.75–2.72); qualitative synthesis reported positive associations for several other cancer sites.
Outcomes measured
- Breast cancer incidence
- Prostate cancer incidence
- Non-Hodgkin lymphoma incidence
- Colorectal cancer incidence
- Pancreatic cancer incidence
- Thyroid cancer incidence
Limitations
- Most studies relied on low-resolution satellite imagery (1–5 km; DMSP) for outdoor ALAN exposure assessment.
- Outdoor ALAN exposure measures lacked information on color of light.
- Substantial heterogeneity was reported in meta-analyses (e.g., I2 values reported for breast and prostate cancer).
- Limited number of studies for some cancer sites (e.g., prostate cancer quantitative synthesis based on 2 studies).
View raw extracted JSON
{
"publication_year": null,
"study_type": "meta_analysis",
"exposure": {
"band": null,
"source": "Indoor and outdoor artificial light-at-night (ALAN)",
"frequency_mhz": null,
"sar_wkg": null,
"duration": null
},
"population": "Participants in observational studies (cohort and case-control) assessing ALAN exposure and cancer incidence",
"sample_size": 2508807,
"outcomes": [
"Breast cancer incidence",
"Prostate cancer incidence",
"Non-Hodgkin lymphoma incidence",
"Colorectal cancer incidence",
"Pancreatic cancer incidence",
"Thyroid cancer incidence"
],
"main_findings": "This systematic review and random-effects meta-analysis included 28 observational studies (2,508,807 individuals). Higher outdoor ALAN exposure was associated with increased breast cancer risk (meta-estimate 1.12, 95% CI 1.03–1.23), while indoor ALAN showed a non-significant positive association with breast cancer (1.07, 0.95–1.21) and no differences by menopausal status. For prostate cancer, the meta-analysis suggested a non-statistically significant increased risk with higher outdoor ALAN (1.43, 0.75–2.72); qualitative synthesis reported positive associations for several other cancer sites.",
"effect_direction": "mixed",
"limitations": [
"Most studies relied on low-resolution satellite imagery (1–5 km; DMSP) for outdoor ALAN exposure assessment.",
"Outdoor ALAN exposure measures lacked information on color of light.",
"Substantial heterogeneity was reported in meta-analyses (e.g., I2 values reported for breast and prostate cancer).",
"Limited number of studies for some cancer sites (e.g., prostate cancer quantitative synthesis based on 2 studies)."
],
"evidence_strength": "high",
"confidence": 0.85999999999999998667732370449812151491641998291015625,
"peer_reviewed_likely": "yes",
"stance": "concern",
"stance_confidence": 0.7199999999999999733546474089962430298328399658203125,
"summary": "This systematic review and random-effects meta-analysis evaluated observational evidence on indoor and outdoor artificial light-at-night (ALAN) exposure and cancer incidence, with a critical appraisal of exposure assessment. Across included studies, higher outdoor ALAN was associated with increased breast cancer risk, while indoor ALAN showed a non-significant positive association and no differences by menopausal status. Evidence for prostate cancer and other cancer sites was suggestive but non-significant or based on qualitative synthesis, and exposure assessment was often limited by low-resolution satellite data and lack of light color information.",
"key_points": [
"The review searched six databases, two registries, and Google Scholar through April 17, 2024.",
"Twenty-eight observational studies were included in qualitative synthesis, totaling 2,508,807 individuals.",
"Outdoor ALAN exposure was associated with breast cancer risk in meta-analysis (meta-estimate 1.12, 95% CI 1.03–1.23).",
"Indoor ALAN exposure showed a non-significant positive association with breast cancer risk (meta-estimate 1.07, 0.95–1.21).",
"No differences in breast cancer associations were reported by menopausal status.",
"For prostate cancer, outdoor ALAN showed a non-statistically significant increased risk in meta-analysis (meta-estimate 1.43, 0.75–2.72).",
"Qualitative synthesis reported positive associations for non-Hodgkin lymphoma and colorectal, pancreatic, and thyroid cancers.",
"A major limitation noted was reliance on low-resolution satellite imagery for outdoor ALAN and lack of information on light color."
],
"categories": [
"Lighting (ALAN)",
"Cancer Epidemiology",
"Environmental Exposure Assessment",
"Systematic Reviews & Meta-analyses"
],
"tags": [
"Artificial Light At Night",
"Outdoor Light Pollution",
"Indoor Light Exposure",
"Breast Cancer",
"Prostate Cancer",
"Non-Hodgkin Lymphoma",
"Colorectal Cancer",
"Pancreatic Cancer",
"Thyroid Cancer",
"Satellite Imagery Exposure Assessment",
"Random-Effects Meta-Analysis",
"Observational Studies",
"Joanna Briggs Institute Appraisal"
],
"keywords": [
"ALAN",
"artificial light at night",
"light pollution",
"breast cancer",
"prostate cancer",
"cancer incidence",
"systematic review",
"meta-analysis",
"exposure assessment",
"satellite images",
"DMSP"
],
"suggested_hubs": [],
"social": {
"tweet": "Systematic review/meta-analysis (28 observational studies; 2.5M people) found higher outdoor artificial light-at-night (ALAN) associated with increased breast cancer risk (RR 1.12). Indoor ALAN showed a non-significant positive association; exposure assessment often relied on low-resolution satellite data.",
"facebook": "A 2024 systematic review and meta-analysis of observational studies (2.5 million participants) reported an association between higher outdoor artificial light-at-night (ALAN) and breast cancer risk. Indoor ALAN showed a non-significant positive association, and the authors noted major limitations in exposure assessment (often low-resolution satellite imagery without light color information).",
"linkedin": "A 2024 systematic review and random-effects meta-analysis (Science of The Total Environment) synthesized 28 observational studies (2.5M participants) on indoor/outdoor artificial light-at-night (ALAN) and cancer incidence. Outdoor ALAN was associated with breast cancer risk (RR 1.12), while indoor ALAN and prostate cancer results were non-significant; exposure assessment quality (e.g., low-resolution satellite data, no light color information) was highlighted as a key limitation."
}
}
AI can be wrong. Always verify against the paper.
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