Non-alcoholic fatty liver disease among patients with sleep disorders: a Nationwide study of Taiwan

Background Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases. Studies have shown that sleep apnea is associated with NAFLD. However, studies on the association between sleep disorders in general and NAFLD are limited. We conducted a nationwide population-based longitudinal study to evaluate this potential association. Methods We identified patients diagnosed with sleep disorders in the years 2000 through 2005 in Taiwan using the National Health Insurance Research Database and selected an equal number of patients without sleep disorders from the same database as the comparison cohort. The patients were followed from the index date to the diagnosis of NAFLD or the end of 2013. We used Cox proportional hazards models to estimate the risk of NAFLD associated with sleep disorders. Results A total of 33,045 patients with sleep disorders were identified. The incidence of NAFLD was 14.0 per 10,000 person-year in patients with sleep disorders and 6.2 per 10,000 person-year in the comparison cohort. The adjusted hazard ratio (AHR) of NAFLD associated with sleep disorders was 1.78 (95% confidence interval [95%CI]: 1.46-2.16), and other independent risk factors included male sex (AHR = 1.31, 95%CI: 1.12-1.54), age 40-59 years (AHR = 1.49, 95%CI: 1.21-1.82), and dyslipidemia (AHR = 2.51, 95%CI: 2.08-3.04). In the subgroup analyses, both patients with (AHR = 2.24, 95%CI: 1.05-4.77) and without (AHR = 1.77, 95%CI: 1.46-2.15) sleep apnea had an increased risk of NAFLD. Conclusions Sleep disorders are associated with NAFLD, even in patients without sleep apnea. Further studies are warranted to explore the mechanisms of the association.