Abstract

Background: Both sleep quality (SQ) and physical activity (PA) are known factors associated with positive health outcomes. Less is known about the extent to which both SQ and PA independently relate to symptoms of depression. The purpose of this study was to examine the ability of SQ and PA to predict scores from the patient health questionnaire (PHQ). Methods: A cross-sectional convenience sample of 6,205 adults was used for this study. Sleep quality was assessed using six questionnaire items asking about sleep time, sleep interruptions, patient-reported sleep issues, and overall sleepiness. Each sleep item was dichotomized to indicate poor sleep quality (PSQ) and summed to create a score from 0 (no PSQ issues) to 6 (maximal PSQ). Four different PA variables were used and included walking and biking for transportation activity (WBTA, min/week), moderate-to-vigorous work activity (MVWA, min/week), moderate-to-vigorous PA (MVPA, min/week), and sedentary time (ST, min/day). The nine-item PHQ served as the outcome variable with discrete scores ranging from 0 (no depression symptoms) to 27 (maximal depression symptoms). Control variables included body mass index (BMI, kg/m²), body shape index (BSI, T-score), age, sex, race, and income. Statistical analyses included a series of competing generalized linear models appropriate for count data that included Poisson, negative binomial, and zero-inflated distributions. Finally, binary logistic regression was used to model zero scores on the PHQ. Results: Approximately 36.0% (95% CI: 34.8 - 37.2) of adults met the weekly requirements for PA guidelines and 8.2% (7.5 - 8.9) met the PHQ criteria for at least moderate depression. In bivariate analyses, PSQ, MVWA, and ST were positively associated and MVPA negatively associated with PHQ scores. The negative binomial model was the best fitting model as judged by AIC, χ²/DF ratio, and parsimony. The fully adjusted model indicated mean PHQ score changed by 0.92 (0.85 – 0.99) for those with some WBTA (compared to none), by 0.88 (0.82 – 0.95) for those in the lowest tertile of MVWA (compared to the highest tertile), by 0.83 (0.76 – 0.91) and 0.86 (0.80 – 0.93) for those in the lowest and middle tertiles (respectively) of ST (compared to the highest tertile), by 1.22 (1.13 – 1.31) for those in the lowest tertile of MVPA (compared to the highest tertile) and by 1.36 (1.32 – 1.39) for each one point increase in PSQ score. Finally, binary modeling of a zero PHQ score indicated the odds of zero changed by 1.20 (1.05 – 1.37) for the highest MVPA tertile (compared to lowest tertile), by 1.30 (1.11 – 1.51) and 1.26 (1.10 – 1.45) for the lowest and middle tertiles (respectively) of ST (compared to the highest tertile), by 0.70 (0.60 – 0.83) and 0.85 (0.74 – 0.97) for the middle and highest tertiles (respectively) of MVWA (compared to the lowest tertile) and by 0.64 (0.61 – 0.67) for each one point increase in PSQ score. Conclusion: Results from this study indicate that inadequate sleep, being active at work, and sedentary behavior predict depression in adults. Additionally, greater amounts of recreational activity may independently protect against symptoms of depression in this population. Health promotion specialists should incorporate sleep quality strategies into physical activity programming.