Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common liver disease worldwide and the leading cause of liver-related morbidity and mortality [1,2]. The global surge in the ageing population, coupled with a rising prevalence of comorbidities like diabetes, hyperlipidemia, obesity, and hypertension, has amplified the incidence of MASLD [3,4]. It can progress to metabolic dysfunction-associated steatohepatitis (MASH) and, in severe instances, lead to cirrhosis, hepatocellular carcinoma (HCC) or death [5]. Despite the considerable economic burden imposed by MASLD, no approved treatments or specific pharmacological interventions have been established to date [6,7]. Therefore, lifestyle modification is the cornerstone for preventing the onset of MASLD and its further progression to adverse liver outcomes.

Sleep, which constitutes approximately one-third of our lives, plays a fundamental role in our overall health, influencing cognitive performance, physiological processes, emotional regulation, physical development, and quality of life [8]. In recent years, the impact of work stress, shift work, academic pressure, and recreational activities has led to a rise in both short and long sleep durations [9]. An expanding corpus of epidemiological research indicates that both short and long sleep durations are pivotal in the development of metabolic disorders—conditions closely intertwined with MASLD and liver cirrhosis [[10], [11], [12], [13]]. However, regarding the association of sleep duration with the risk of MASLD [[14], [15], [16]], epidemiological studies have provided conflicting findings, with limitations such as cross-sectional study design, small sample size, and short follow-up period [[17], [18], [19]]. Moreover, the association between sleep duration and the risk of adverse liver outcomes are still understudied.

In light of these gaps, we conducted this large prospective cohort study to provide epidemiological evidence for the association of sleep duration with MASLD and adverse liver outcomes, including cirrhosis, HCC, and liver-related mortality.