The global epidemiology of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH): a systematic review

Background and Aims: NAFLD is a leading cause of liver-related morbidity and mortality. We assessed the global and regional prevalence, incidence, and mortality of NAFLD using an in-depth meta-analytic approach. Approach and Results: PubMed and Ovid MEDLINE were searched for NAFLD population-based studies from 1990 to 2019 survey year (last published 2022) per Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Meta-analysis was conducted using random-effects models. Bias risk assessment was per Joanna Briggs Institute. Of 2585 studies reviewed, 92 studies (N=9,361,716) met eligibility criteria. Across the study period (1990–2019), meta-analytic pooling of NAFLD prevalence estimates and ultrasound-defined NAFLD yielded an overall global prevalence of 30.05% (95% CI: 27.88%–32.32%) and 30.69% (28.4–33.09), respectively. Global NAFLD prevalence increased by +50.4% from 25.26% (21.59–29.33) in 1990–2006 to 38.00% (33.71–42.49) in 2016–2019 ( p <0.001); ultrasound-defined NAFLD prevalence increased by +38.7% from 25.16% (19.46–31.87) in 1990–2006 to 34.59% (29.05–40.57) ( p =0.029). The highest NAFLD prevalence was in Latin America 44.37% (30.66%–59.00%), then Middle East and North Africa (MENA) (36.53%, 28.63%–45.22%), South Asia (33.83%, 22.91%–46.79%), South-East Asia (33.07%, 18.99%–51.03%), North America (31.20%, 25.86%–37.08%), East Asia (29.71%, 25.96%–33.76%), Asia Pacific 28.02% (24.69%–31.60%), Western Europe 25.10% (20.55%–30.28%). Among the NAFLD cohort diagnosed without a liver biopsy, pooled mortality rate per 1000 PY was 12.60 (6.68–23.67) for all-cause mortality; 4.20 (1.34–7.05) for cardiac-specific mortality; 2.83 (0.78–4.88) for extrahepatic cancer-specific mortality; and 0.92 (0.00–2.21) for liver-specific mortality. Conclusions: NAFLD global prevalence is 30% and increasing which requires urgent and comprehensive strategies to raise awareness and address all aspects of NAFLD on local, regional, and global levels.