Active and passive smoking and the risk of breast cancer: An umbrella review of systematic reviews and meta-analyses
Abstract
BACKGROUND
Smoking, both active and passive, has been associated with an increased risk of numerous cancers worldwide, yet its impact on breast cancer remains a subject of debate. While many studies have explored the link between smoking and breast cancer risk, the findings have been inconsistent and often contradictory. To clarify the nature and strength of the association between smoking exposure (current, former, and passive) and breast cancer, we conducted an umbrella review of meta-analyses of observational studies (PROSPERO registration number: CRD42024610213).
METHODS
We conducted a systematic literature search in PubMed, Scopus, and Web of Science from inception to October 24, 2024, and manually screened reference lists. Systematic reviews and meta-analyses of observational studies (cohort, case-control, and/or cross-sectional) examining the association between smoking (current, former, and passive) and breast cancer were included. Predefined evidence classification criteria were applied to assess the credibility of associations, graded as convincing (class I), highly suggestive (class II), suggestive (class III), weak (class IV), or no evidence (class V). Data were extracted for effect estimates, heterogeneity (I²), 95 % prediction intervals, small study effects, and excess significance bias, using random-effects models and AMSTAR 2 to evaluate methodological quality.
FINDINGS
We identified 1095 articles, of which eight meta-analytic systematic reviews, encompassing…
How strong is the evidence?
Evidence Hub reads this as a meta-analysis. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid.
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