Comparison of long-term prognosis between non-obese and obese patients with non-alcoholic fatty liver disease

Background and Aim: Non-alcoholic fatty liver disease (NAFLD) can progress in non-obese patients as in obese patients. Reports on long-term prognosis in non-obese NAFLD patients are controversial. Therefore, we aimed to examine the long-term prognosis of non-obese patients with NAFLD. Methods: This single-center, retrospective cohort study enrolled biopsy-proven non-obese and obese NAFLD patients between January 2002 and December 2011 and followed them up until 31 March 2021, for death and clinical events (cardiovascular and liver-related events and extrahepatic cancers). Results: Of the 223 NAFLD patients, 58 (26.0%) were non-obese. Compared with obese patients, they had a lower fibrosis stage (0.8 +/- 0.80 vs 1.2 +/- 0.91; P = 0.004), milder lobular inflammation (0.9 +/- 0.7 vs 1.1 +/- 0.7; P = 0.02), and significantly lower serum creatinine, total bilirubin, ferritin, and type IV collagen 7S and higher high-density lipoprotein levels. After a median follow-up of 8.9 years, no significant difference was noted in mortality between the two groups (2 [3.4%] non-obese vs 5 [3.0%] obese; log-rank test, P = 0.63). Twelve patients (20.7%) in the non-obese group and 32 (19.4%) in the obese group had clinical events. Although the obese group had a higher incidence of clinical events during the first 10 years of follow-up, the non-obese group had a higher incidence after that (log-rank test, P = 0.67). The non-obese group had a high incidence of malignancy (9 [15.5%] non-obese vs 14 [8.3%] obese; P = 0.13). Conclusion: Non-obese NAFLD does not necessarily have a good prognosis, and some cases have a poor prognosis such as extrahepatic cancers. Further validation is required in the future.