The Association between Changes in Psychosocial Working Conditions and Body Weight Change : A Follow-up Study among Midlife Employees | Työn psykososiaalisten kuormitustekijöiden muutoksen yhteys merkittävään painon nousuun keski-ikäisillä työntekijöillä

Introduction: Working conditions have not only been found to impact work ability and productivity, but the overall health of employees. The working environment is a relevant health factor for a considerable part of the population. In research, work-related mental strain has been associated with body weight change, yet no causal relationship can be confirmed based on the existing evidence. Of the psychosocial factors, low job control, as well as both high and low job demands have been associated with weight gain. Most of the research so far has been done with cross-sectional data; long-term follow-ups are scarce and only little research has been done on the association between changing working conditions and body weight change. Aim: The general aim of this study was to examine the association between changes in psychosocial working conditions and body weight change among midlife women and men. The association between two psychosocial work characteristics, job demands and job control, and weight gain during the follow-up was examined in a cohort study among the employees of the City of Helsinki in Finland. The main research question was: (i) Is change in job demands and job control associated with major weight gain during a 10- to 12-year follow-up period among midlife employees? In addition, the contribution of several background and lifestyle factors were taken into account. Especially the contribution of baseline BMI-status, dietary habits and leisure-time physical activity to the association between psychosocial working conditions and major weight gain was studied. Methods: The data were collected from a mail survey among the employees of the City of Helsinki in 2000–2002, 2007 and 2012. The study sample consisted of employees who were 40, 45, 50, 55 and 60 years old at the beginning of the survey in 2000–2002. Exclusion criterions were BMI <18.5kg/m2 in phase 1, retiring before phase 2, and drop out before phase 3. Hence, the final study sample (n=4,630) consisted 52% of the original study population, of which 83% were women. Psychosocial working conditions were assessed with a validated Job Content Questionnaire (JCQ) by Karasek and Theorell in phase 1 and 2. Weight change was assessed between phases 1 and 3, and major weight gain was defined as at least 10% weight gain during that time period. Dietary habits were assessed using a 20-item Food Frequency questionnaire (FFQ). Based on the current national dietary recommendations, nine food habits were chosen and their usage frequency was used as a determinant of healthy food habits. Leisure time physical activity was assessed with metabolic equivalent tasks (METs). Logistic regression analysis was used to examine the associations between changing job demands, job control, and major weight gain. All the analyses were stratified by gender. In addition, further stratification was made by the baseline BMI. Results: Weight gain was common among the study population. Major weight gain was observed among 27% of women and 15% of men. A weak association between change in job demands and major weight gain was found among both genders. Among women, the risk of major weight gain was higher among those who reported persistent high job demands (OR 1.22 95% CI 1.02–1.48 full adjusted model) compared with those with persistent low job demands. Among men, in contrast, the risk was higher among those who reported decreased job demands compared with those who reported persistent low job demands (OR 1.80 95% CI 1.02–3.16 full adjusted model). When further stratified by the BMI in phase 1, the risk was higher only among overweight or obese women, whereas among men the increase in risk was seen among both normal weight and overweight or obese participants. Dietary habits and leisure time physical activity did not affect the association of changing psychosocial working conditions with major weight gain. However, they had a minor own effect on the risk. Change in job control was not associated with the risk of major weight gain. Conclusions: The study shows that change in job demands is weakly associated with major weight gain. Future research is needed especially among other employers than municipalities, and especially among men. Changing working conditions should be studied with shorter follow-up periods, while taking into account also the role of social support at the workplace.