“…Potential confounders from the baseline questionnaire included age (continuous variable), back injury during the previous year (yes/no), body mass index (BMI) (kg/ m 2 , continuous variable), smoking status (dichotomous variable depicting smoker/non-smoker), leisure-time physical activity (4-categories from low to a very high level) (22,23), seniority (years working as healthcare worker, continuous variable), and influence at work from the Copenhagen Psychosocial Questionnaire (COPSOQ normalized on a 0-100 scale according to the test score manual) (24,25).…”