Metabolic dysfunction-associated fatty liver disease (MAFLD) is a significant global health concern, affecting nearly 25% of adults. Its prevalence is increasing, particularly in China. MAFLD can lead to serious liver diseases and extrahepatic complications, imposing a substantial burden on healthcare systems. Physical inactivity and poor sleep quality, increasingly prevalent in modern societies, are independently linked to various metabolic dysfunctions, including MAFLD. Sufficient physical activity improves insulin resistance and body weight, key factors in MAFLD management. Conversely, several aspects of poor sleep quality, such as short sleep duration, insomnia, and snoring, are associated with metabolic disorders. PA and sleep quality are interconnected, potentially influencing metabolic homeostasis through shared pathways. For example, PA can affect sleep duration and circadian rhythm, and extended sleep may reduce PA. While individual associations between PA, sleep quality, and MAFLD have been observed, research on their combined effects is limited. This study aims to investigate the combined impact of PA and a comprehensive assessment of sleep quality (including daytime napping, common in China) on MAFLD risk in Western China.

Existing research indicates independent negative associations between physical inactivity and poor sleep quality with various metabolic dysfunctions and MAFLD. Studies show that sufficient physical activity (PA) helps improve insulin resistance and maintain a healthy body weight, both crucial for managing MAFLD. Conversely, poor sleep quality, including short sleep duration, insomnia, and snoring, is positively associated with metabolic disorders. The interrelationship between PA and sleep quality is complex, with PA potentially impacting sleep duration and circadian rhythms, and vice versa. While studies have shown independent links between PA, sleep quality, and MAFLD, joint effects remain largely unexplored, particularly considering the prevalence of daytime napping in certain populations like those in Western China.

This population-based cross-sectional study used data from the Population-based Cohort study of Chronic Diseases in Xinjiang (PCCDX), conducted between July 2019 and September 2021. 12,295 participants aged 30-74 were initially enrolled. After excluding participants due to insufficient data for MAFLD diagnosis, history of liver diseases, extreme outlier values for waist circumference and BMI, and missing sleep behavior data, the final analysis included 10,089 participants. MAFLD was diagnosed radiologically via liver ultrasound. Sleep behaviors were assessed using the Pittsburgh Sleep Quality Index (PSQI), creating a composite score representing overall sleep quality. Physical activity was assessed using the International Physical Activity Questionnaire (IPAQ), measuring total weekly metabolic equivalent (MET). PA was categorized as low, moderate, and high, and also based on whether it met WHO recommendations for MVPA. Statistical analysis included linear and logistic regression models, restricted cubic splines to assess non-linear relationships, and multiple imputation for missing data. The study adjusted for various confounding factors such as age, gender, education, marital status, smoking, alcohol consumption, sedentary time, dietary diversity, and BMI. Sensitivity analyses were performed to assess robustness.

Of the 10,089 participants (mean age 47.0 years, 51.6% male), 3854 (38.2%) had MAFLD. Poor sleep quality and physical inactivity were independently and jointly associated with increased MAFLD prevalence. Compared to those with guideline-recommended MVPA and good sleep quality, individuals with no recommended MVPA and poor sleep had a significantly higher odds of MAFLD (OR = 2.36, 95% CI: 1.81–3.08). Improving sleep quality substantially reduced MAFLD prevalence regardless of PA levels. Engaging in PA above the guidelines did not fully offset the negative effects of poor sleep on MAFLD. In subjects with high PA, poor sleep increased MAFLD prevalence by 153%. In most individuals with moderate PA, even a moderate reduction in sleep quality increased MAFLD prevalence by 20%. Sensitivity analyses confirmed these findings.

This study demonstrates a significant interaction between PA and sleep quality in relation to MAFLD prevalence. The highest MAFLD prevalence was observed in individuals with poor sleep quality and low/moderate PA. Good sleep quality provided additional protection against MAFLD, even among those with high PA. Importantly, exceeding WHO's recommended MVPA did not fully mitigate the negative effects of poor sleep on MAFLD. The high MAFLD prevalence in this study (38.2%) is slightly higher than the national average, possibly due to factors like lower PA levels and poorer sleep quality compared to other populations. The study highlights the significant impact of both sleep and PA on MAFLD. It emphasizes the importance of considering both lifestyle factors, and suggests that interventions targeting both may be more effective than those addressing only one.

This study underscores the importance of addressing both poor sleep quality and insufficient physical activity in preventing MAFLD. Interventions targeting both behaviors may be more effective than those focusing solely on one. Future research should explore the causal relationships and underlying biological mechanisms. Further studies in diverse populations are also needed to confirm these findings.

The cross-sectional design limits the ability to establish causality. Self-reported data on sleep and PA may be subject to recall bias and misclassification. While ultrasound is widely used, it does not provide histological confirmation of MAFLD. Despite these limitations, sensitivity analyses reinforced the study's key findings.