Abstract
BACKGROUND: Unhealthy lifestyles, which include unhealthy diet and unhealthy sleep duration, have been widely recognized as modifiable risk factors for depressive symptoms. This study aims to explore the associations between dietary quality, sleep duration, and depression symptoms, as well as their combined effects. METHODS: The NHANES 2007 to 2014 cycles provided the data for this study, in which 19,134 adults aged 20 years and older were included. Unhealthy diet, measured using an average Healthy Eating Index (HEI)-2015 score below the 60th percentile, and unhealthy sleep duration, measured as sleep duration at night less than 7 h or greater than/equal to 9 h, were the primary exposures. Then participants were divided into four different lifestyles. A weighted-multivariable logistic regression was employed, controlling for relevant variables. Furthermore, stratified analyses were conducted to assess the robustness of the findings and identify potential high-risk groups. RESULTS: The overall prevalence of depressive symptoms among all participants was 8.44%. Among the participants, 56.58% met the criteria for healthy sleep duration, and 24.83% scored at or above the 60th percentile on the HEI-2015. Unhealthy diet (OR: 1.40, 95% CI: 1.18-1.67, p < 0.001) and unhealthy sleep duration (OR: 1.94, 95% CI: 1.63-2.31, p < 0.001) exhibited positive associations with depression symptoms. Individuals who maintained an unhealthy diet but healthy sleep duration (OR: 1.60, 95% CI: 1.20-2.13, p = 0.002), healthy diet but unhealthy sleep duration (OR: 2.50, 95% CI: 1.64-3.80, p < 0.001), or an unhealthy diet and unhealthy sleep duration (OR: 2.91, 95% CI: 2.16-3.92, p < 0.001) were significantly associated with depressive symptoms compared to those with a healthy diet and healthy sleep duration, respectively. In stratified analyses, females, middle-aged individuals, those with a college degree or higher education, and individuals who do not meet the recommended level of physical activity exhibit heightened susceptibility to depressive symptoms when exposed to unhealthy diet and unhealthy sleep duration. CONCLUSION: In summary, our study suggests that individuals affected by the individual and synergistic effect of an unhealthy diet and unhealthy sleep duration are more susceptible to experiencing depressive symptoms.