[The search for a predictor of deterioration of the nonspecific stress index K6 among urban residents: The KOBE study].

Objective　To explore health-related and socioeconomic factors that can predict future deterioration in Psychological Distress Scale (K6) scores.Method　We conducted a baseline (2010, 2011) self-administered questionnaire survey of the Kobe Orthopedic and Biomedical Epidemiological study (KOBE study) involving 1,117 participants who had no previous history of cancer or cardiovascular diseases and were not under treatment for hypertension, diabetes, or dyslipidemia. We used the Japanese K6 as an indicator of stress and defined K6≧5 points as a high-stress group and K6<5 points as a low-stress group. A four-year follow-up survey (2014, 2015) was conducted on 1,004 people (follow-up rate of 90%). We excluded 39 participants with missing values, and 185 people whose K6 score was higher than 5 points at baseline. A final total of 780 participants' scores were examined for: gender, age, living situation, physical activity level, average sleep time, as well as the K6 score, the Japanese Hearing Handicap Inventory for Elderly (HHIE-S), and the Japanese Oswestry Disability Index (ODI). We conducted a logistic regression analysis using K6≧5 points at the four-year follow-up survey as the dependent variable and each factor at the baseline survey as the independent variable.Results　Of the 780 subjects analyzed, 132 (16.9%) were highly stressed (K6≧5 points) at the four-year follow-up point. A logistic regression analysis found age (40s/70s) (odds ratio 3.38, 95% confidence interval 1.45-7.86), living situation (single/living together) (odds ratio 1.98, 95% confidence interval 1.07-3.68), and ODI scores (every 1%) (odds ratio 1.05, 95% confidence interval 1.01-1.09), to all be significantly associated with high stress.Conclusion　This study suggests that age, living situation, and ODI scores are related to future stress.