Sleep characteristics of middle-aged adults with non-alcoholic fatty liver disease: findings from the Shahrekord PERSIAN Cohort Study

Background: Several studies have reported short sleep duration in people with non-alcoholic fatty liver disease (NAFLD) but other sleep characteristics have been less studied. We aimed to assess the association of NAFLD with sleep duration and quality in an Iranian population sample. Methods: We used data from 9,151 participants in the Shahrekord Prospective Epidemiological Research Studies in Iran (PERSIAN) Cohort Study, including 1,320 diagnosed with NAFLD. Log-binomial regression models sequentially adjusted for sociodemographic, lifestyle, clinical and biological variables were used to estimate relative risks (RR) and 95% confidence intervals (95% CI) for the association between NAFLD and sleep characteristics. Results: Participants with NAFLD had shorter sleep duration, later wake-up time and bedtime, worse sleep efficiency, and more frequent daytime napping and use of sleeping pills, in age- and sex-adjusted models. After controlling for sociodemographic, lifestyle, clinical, and biological variables the associations remained strong for sleep efficiency (per 10%, RR=0.92, 95%CI: 0.88-0.96) and use of sleeping pills (RR=1.48, 95%CI: 1.17-1.88). The association between NAFLD and sleep efficiency was stronger in participants aged >60 years (RR=0.81, 0.70-0.93) and 40-60 years (RR=0.87, 0.82-0.94), compared with those aged <40 years (P-heterogeneity<0.001). Daytime napping in participants with NAFLD was observed in males but not females (P-heterogeneity=0.007), and in those with body mass index (BMI)<30 but not in obese participants (P-heterogeneity<0.001). Conclusions: Diagnosis of NAFLD is associated with several poor sleep characteristics in middle-aged Iranians. Although longitudinal studies would help to clarify the direction of causality, our study shows that poor sleep is an important aspect of NAFLD.