The relationship between tobacco and non-alcoholic fatty liver disease incidence: a systematic review and meta-analysis of observational studies
Abstract
Background This meta-analysis investigates the relationship between smoking and non-alcoholic fatty liver disease (NAFLD) risk. Methods Observational studies (cohort, case-control, cross-sectional) were systematically searched in PubMed, Web of Science, EBSCO, and Cochrane Library up to December 2024. Adjusted odds ratio (OR) and corresponding 95% confidence interval (95% CI) were used to assess the association. Results A total of 19 studies, composing 450,130 participants were included. Active smoking significantly increased NAFLD risk (OR = 1.30, 95% CI: 1.21–1.40, p < 0.001), with stronger effects observed in current smokers (OR = 1.41, 95% CI: 1.22–1.63, p < 0.001). A dose-response relationship was evident: ≥20 pack-years of smoking elevated risk by 32% (OR = 1.32, 95% CI: 1.18–1.49, p < 0.001). Subgroup analyses revealed amplified risks in metabolically compromised individuals, including those with BMI ≥ 24 (OR = 1.43, p < 0.001), TG ≥ 1.2 mmol/L (OR = 1.41, p = 0.003), and SBP ≥ 125 mmHg (OR = 1.65, p < 0.001). Passive smoking showed a marginal association (OR = 1.13, 95% CI: 1.09–1.16, p < 0.001). Conclusion Smoking is an independent risk factor for NAFLD, particularly in individuals with metabolic dysregulation. Public health strategies targeting smoking cessation and metabolic control may mitigate NAFLD burden. Systematic review registration https://www.crd.york.ac.uk/prospero/#loginpage, identifier CRD42024545970
How strong is the evidence?
Evidence Hub reads this as a meta-analysis, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 450,130 participants or records.
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