# The relationship between tobacco and non-alcoholic fatty liver disease incidence: a systematic review and meta-analysis of observational studies

## TL;DR

This study finds that smoking increases the risk of non-alcoholic fatty liver disease, especially in people with metabolic issues.

## Contribution

The study establishes a dose-response relationship between smoking and NAFLD risk, highlighting amplified effects in metabolically compromised individuals.

## Key findings

- Active smoking increases NAFLD risk by 30% with stronger effects in current smokers.
- Subgroup analyses show amplified risks in individuals with BMI ≥ 24, TG ≥ 1.2 mmol/L, and elevated SBP.
- Passive smoking shows a marginal association with increased NAFLD risk.

## Abstract

This meta-analysis investigates the relationship between smoking and non-alcoholic fatty liver disease (NAFLD) risk.

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.

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).

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.

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