Liver-related Mortality is Increased in Lean Subjects with Non- alcoholic Fatty Liver Disease Compared to Overweight and Obese Subjects.

Background And Aims: Although non-alcoholic fatty liver disease (NAFLD) is linked to obesity, a proportion of lean subjects also have NAFLD with potentially distinct clinical features. We studied the outcome of lean NAFLD subjects.

Methods: 299 consecutive patients (215 male, 84 female, 49.5 ± 13.5years) with biopsy-proven NAFLD and a follow-up of 8.4 years (±4.1; range: 0.9-18.0) were stratified by body mass index (BMI) at the time of liver biopsy: lean (BMI ≤25.0 kg/m, n=38), overweight (BMI 25.0-29.9 kg/m2, n=165), obese (BMI ≥30.0 kg/m2, n=93). A control group of 1,013 subjects (547 male, 52.4 ± 5.8) was used for comparison. The time to the event was recorded. Multivariable Cox regression analyses were performed to assess associations with 10-year-mortality. Hazard ratios (HR) and adjusted hazard ratios (aHR) with 95% confidence intervals (CI) were calculated.

Results: Age and gender were similar, while components of the metabolic syndrome were less frequent in lean subjects. The proportion of subjects with significant fibrosis and the number of subjects with cirrhosis was increased in lean subjects while the proportion of non-alcoholic steatohepatitis was not different. Mortality in the NAFLD groups was significantly higher than in the control group. Multivariable analysis adjusting for age, gender, and glucose confirmed lower mortality in overweight (aHR 0.21; 95% CI 0.07-0.62, p=0.005) and in obese (aHR 0.22; 95% CI 0.06-0.76, p=0.02) compared to lean subjects. Further adjustment for fibrosis weakened the difference between lean and obese (p=0.12) while the difference to overweight subjects remained intact (p=0.01).

Conclusion: Lean subjects with NAFLD have a high risk of liver-related death. Our data support that lean NAFLD subjects deserve particular attention with regard to clinical follow-up.