Lifestyle determinants of depressive feeling and a feeling of unhappiness among workers: a study in Japan.

BACKGROUND: Lifestyle determinants of depressive state and a feeling of unhappiness in daily life were evaluated among the workers in Japan by adjusting obesity and age.
METHODS: A total of 3630 men aged 34 to 60 years from a workplace in Japan participated in this cross-sectional study conducted in 2006. The prevalence of depressive state and a feeling of unhappiness were evaluated by a questionnaire with questions pertaining to the age, body mass index, and six lifestyle factors. The six lifestyle factors were frequency of exercise and alcohol intake per week, smoking habit, hours of sleep per day, and frequency of eating breakfast and snack per week. The associations between depressive state and/or a feeling of unhappiness and the lifestyle factors were tested by logistic regression analysis.
RESULTS: The prevalence of depressive state and a feeling of unhappiness among the workers was 8.1% and 20.3%, respectively. The prevalence of workers who sleep at least for 6 hours on average, exercise regularly and eat breakfast everyday increased as the age of the workers increased. Depressive state and a feeling of unhappiness were significantly associated with age and a reduced duration of sleep even after adjustment for the other variables. No significant associations were found between the other lifestyle factors examined and depressive state and/or a feeling of unhappiness.
CONCLUSIONS: Depressive state and/or a feeling of unhappiness were significantly associated with a reduced duration of sleep among the workers. Aging was a preventative factor of depressive state and/or a feeling of unhappiness. The effect of obesity was adjusted in this study, but the cause-effect relation between lifestyles and depressive state and/or a feeling of unhappiness should be clarified by the follow-up study.