To the best of our knowledge, this study marks the first exploration of gender disparities in the relationship between various domains of physical activity, sleep duration, and depressive symptoms within a large-scale, nationally representative study. In this nationally representative sample of U.S. adults, substantial disparities in the quartiles of Physical Activity (PA) were observed between men and women. Notably, the prevalence of depression among women was almost twice that of men, necessitating separate analyses for each gender. In our independent associations, higher levels of physical activity and normal sleep duration were both significantly associated with a reduced risk of depressive symptoms in both men and women. Moreover, our joint association analysis revealed a significant interaction between physical activity and sleep duration in relation to depression, which was significant in men but not in women. Nevertheless, higher physical activity remained associated with a reduced risk of depression in both genders.
Depression is a prevalent, disabling mental disorder globally, and suicide rates continue to rise, making it the tenth leading cause of death in the United States.26 Consequently, the prevention and treatment of depression are of paramount importance. A psychiatric meta-analysis on lifestyle factors found consistent evidence for the usefulness of physical activity in primary prevention and clinical treatment of various mental disorders, while also highlighting poor sleep as a risk factor for mental illnesses.8 Park and Zarate underscored the significance of sleep and behavioral activation in the treatment of depression,27 mirroring our findings on the independent associations between physical activity (PA), sleep duration, and depressive symptoms.
Numerous studies have linked physical activity with the prevention and treatment of depression. For instance, a Mendelian randomization analysis suggested that increasing physical activity might be an effective strategy for preventing depression.6 A prospective cohort study highlighted the importance of reducing sedentary behavior and increasing light physical activity during adolescence as a public health intervention to reduce the incidence of depression.7 Another cohort study revealed that even modest changes in physical activity levels among a relatively sedentary population may have substantial public mental health benefits, preventing a substantial number of new cases of depression.28 Vancampfort et al. emphasized the necessity of interventions targeting physical inactivity and sedentary behavior, particularly in severe mental illness patients, given the established benefits of physical activity for overall health.29 Moreover, multiple studies have identified a connection between sleep and depression. Goldstein and Walker, for instance, highlighted the role of sleep in emotional brain function as early as 2014.30 Plante found a close association between sleep disturbances and depression, with a bidirectional relationship.31 Ben et al. suggested that even moderate reductions in sleep duration in the general population were associated with daily increases in anxiety,32 a related risk factor for depression. In summary, there is ample evidence supporting the role of physical activity and good sleep as beneficial lifestyle factors for mental health. A recent study of 287,282 participants from the UK Biobank further confirmed the importance of a healthy lifestyle. Researchers employed Mendelian randomization to establish a causal relationship between lifestyle and depression and discovered a wide array of brain regions and peripheral biomarkers associated with lifestyle, including the pallidum, precentral cortex, triglycerides, and C-reactive protein.33
Gender differences have been observed in various fields, such as cardiovascular health and physical activity. O'Neil et al. discussed the role of gender in psychosocial stress and explored potential biological pathways, with a particular focus on autonomic nervous function, which could support gender as a social determinant of cardiovascular health.34 In the context of cardiovascular disease, Xia et al. found substantial gender disparities in primary and secondary prevention across seven geographic regions in China, especially among women.35 Regarding physical activity, a meta-analysis revealed no gender differences in adherence to PA guidelines among adolescents but significant differences among adults and Type 2 diabetes patients, with women consistently engaging in lower levels of moderate-to-vigorous physical activity throughout the lifespan,36 mirroring the physical activity differences observed in our study. In the context of depression, Kuehner noted that women were twice as likely to experience depression throughout their lifetime compared to men,37 a finding consistent with our sample. Another meta-analysis suggested that gender differences in the severity of depression were more pronounced in countries with higher gender equality, with no differences in depressive symptoms; nonetheless, male depression should not be disregarded.38 In light of these gender disparities in cardiovascular health, physical activity, and depression, our study opted for separate analyses for men and women to avoid interference from these factors. Similarly, gender differences were observed in our study as well.
Our study offers several strengths. Firstly, it draws from a large, nationally representative dataset. The sampling methodology of NHANES ensured that our sample was randomly selected and represented the entire U.S. population, enabling us to investigate the relationships between physical activity, sleep duration, and depressive symptoms in the adult population of the United States. Secondly, the sample was stratified by gender to account for differences in physical activity and depression between men and women, thereby minimizing potential biases. Thirdly, we conducted separate analyses for men and women, unveiling gender differences in the joint association between physical activity, sleep duration, and depressive symptoms. Nonetheless, our study has certain limitations. Firstly, due to its cross-sectional design, it cannot establish causation, which underscores the need for further prospective and Mendelian randomization studies to evaluate the potential role of physical activity and sleep duration in depression and validate our findings. Secondly, sleep duration, physical activity domains, and depression were self-reported, potentially introducing recall bias and lack of objectivity. Future research should involve clinical assessment data to validate our findings.