This population-based study revealed that almost one-tenth of rural-dwelling Chinese older adults (age ≥ 65 years) suffered from EDS. Overall, the prevalence of EDS decreased with advanced age, and males had a higher prevalence of EDS than females overall and across all age groups. The presence of depressive symptoms, high OSA risk, and poor sleep quality were related to an increased prevalence of EDS, whereas hypertension was correlated with a decreased prevalence of EDS.

The overall prevalence of EDS in our sample (9.3%) was comparable to the report from the Honolulu-Asian Aging Study of Japanese-American men (8.9%) [4]. However, the Mayo Clinic Study of Aging (age ≥ 70 years, 72.1% male) revealed a much higher prevalence of EDS (22.3%) [6]. The differences in study participants’ characteristics (e.g., age, race, sex, education, and residential areas) may be partially responsible for the different prevalences of EDS across studies.

Our study showed a decreased prevalence of EDS along with increasing age, aligning with the results from meta-analysis and several population-based studies [7]. We found that EDS was more common in males than in females, which was consistent with previous reports [3, 8]. Epidemiological studies have indicated that OSA is a strong risk factor of EDS, and the prevalence of OSA was significantly higher in males than in females [9]. Moreover, EDS is related to increased risk of mortality, suggesting selective survival bias may be subject to the observed cross-sectional associations [10].

We observed that hypertension was correlated with a decreased prevalence of EDS, which was in agreement with a population-based study from Lausanne, Switzerland [11]. The sympathetic nervous system may be more active in people with hypertension, which could lead to a state of heightened arousal [12], but the underlying mechanisms require further investigation.

We observed that the prevalence of EDS was associated with depressive symptoms, independent of multiple potential confounders. A cross-sectional study of Japanese-American men residing in Hawaii showed a higher prevalence of EDS in people with depressive symptoms than those without [4]. The potential mechanisms that may contribute to the association included alterations in the homeostatic regulation, circadian regulation of physiological pathways, and abnormalities in the neuroendocrine system [13].

Our study found a correlation between poor sleep quality and EDS, which was similar to the report from previous studies [2, 11]. Poor sleep quality can lead to overall insufficient sleep and EDS. Furthermore, we discovered that high OSA risk was correlated with higher prevalence of EDS. The Penn State study found an association between OSA and EDS [14]. A possible explanation could be that chronic intermittent hypoxia and fragmented sleep of OSA can cause oxidative damage, neuronal damage, and cell loss in wake-promoting brain regions, which could eventually lead to EDS [15].

A major strength of our study is the large sample of older adults from a Chinese rural community. Furthermore, the EDS condition was subjectively evaluated using the ESS, a widely recognized and validated questionnaire commonly employed in both clinical and research settings. Several limitations are inherent in this study. First, EDS and the variables analyzed cannot be causally related due to the cross-sectional nature of the study. Second, some factors (e.g., lifestyle factors, health history, and use of medications) relied on self-reported data, which could lead to information bias. Third, although multiple potential confounding factors were controlled for in our study, residual confounding effect may still play a part owing to the lack of some unknown or unmeasurable confounding variables (e.g., social status and fatigue) [3, 8].

In summary, our population-based study found that EDS affected nearly one-tenth of Chinese elderly living in rural areas. In addition, the decreased likelihood of EDS was associated with older age, female sex, and hypertension; while the increased likelihood of EDS was related to depressive symptoms, high OSA risk, and poor sleep quality. Future longitudinal studies should explore clinically manageable factors and modifiable lifestyle factors of EDS, which may help develop the preventive and treatment interventions.