Fatigue is associated with depression independent of excessive daytime sleepiness in the general population.

This study aimed to investigate sleep problems and comorbid conditions associated with fatigue in the general population. The data were obtained from a nationwide cross-sectional survey conducted in 2018. The Fatigue Severity Scale was used to assess fatigue. We examined sleep habits, such as workday sleep duration, chronotype, and free-day catch-up sleep, excessive daytime sleepiness (EDS), depression, and other comorbid conditions. We conducted multiple logistic regression analysis with the presence of fatigue as a dependent variable. Of 2,493 adults aged 19 to 92 years, 50% men, mean age was 47.9 ± 16.4 years. The average workday sleep duration was 7.1 ± 1.1 h, and the prevalence of fatigue was 31%. After adjusting for potential confounders, fatigue was associated with EDS (odds ratio [OR] 3.751, 95% confidence interval [CI] 2.928–4.805), depression (OR 3.736, 95% CI 2.701–5.169), perceived insufficient sleep (OR 1.516, 95% CI 1.249–1.839), free-day catch-up sleep (OR 1.123, 95% CI 1.020–1.235), less alcohol intake (OR 0.570, 95% CI 0.432–0.752), and physical inactivity (OR 0.737, 95% CI 0.573–0.948). On subgroup analysis, fatigue was additionally associated with short workday sleep duration (OR 0.899, 95% CI 0.810–0.997) in individuals without EDS. However, among those with EDS, only depression (OR 2.842, 95% CI 1.511–5.343) and less alcohol intake (OR 0.476, 95% CI 0.247–0.915) were associated with fatigue. Fatigue was significantly associated with depression independent of EDS. Further research is warranted to better understand the pathophysiological relationship between fatigue, depression, and sleep.