Table S1 - Potential Risk Factors of Persistent Low Back Pain Developing from Mild Low Back Pain in Urban Japanese Workers

Crude odds ratios of the baseline factors for persistent low back pain (LBP) with work disability. OR: odds ratio, CI: confidence interval, BMI: body mass index, LBP: low back pain. a Obesity: BMI of ≥ 25 is defined as obesity in Japan. b Smoking habits: Brinkmann index of ≥ 400 was defined as heavy smoker, calculated from the total number of cigarettes smoked per day multiplied by duration of smoking in years [45]. c Working hours: ≥ 60 hours per week was assumed to be uncontrolled overtime. d Bending, twisting, lifting, and pushing: ≥ half of the day was considered frequent. e Hours of desk work: longer than 6 hours per day was considered as static posture. f Work-related stress factors assessed with the brief job stress questionnaire: not feeling stressed, feeling stressed: the 5 original responses were reclassified into “not feeling stressed”, where low, slightly low and moderate were combined, and “feeling stressed”, where slightly high and high were combined. g Monotonous task: feelings of monotony or boredom at work. (DOC)