Body weight and mental health : a follow-up study on health functioning and work disability

Obesity and mental ill-health are both major public health issues. More than half of sickness absence days and two-thirds of disability retirements in Finland are caused by mental disorders and musculoskeletal diseases, the latter often associated with obesity. Although some studies have shown a bidirectional association between obesity and mental health, the role of it in a working cohort is unclear. This study aimed to examine the association between body weight and subsequent mental health among midlife employees. In addition to baseline body mass index (BMI), it also examined weight change (Substudies II and III) and the joint association of overweight and common mental disorders (Substudy IV). Mental health outcomes included both self-reported information on mental health functioning and register-based data on psychotropic medication purchases, sickness absence due to mental disorders and disability retirement due to mental disorders. In parallel to mental health, Substudies II–IV also studied physical health functioning and work disability in general and due to musculoskeletal diseases. This study is part of the Helsinki Health Study (HHS), a cohort study set up in 2000–2002 (N=8960, response rate 67%) in order to examine the health of 40–60-year-old employees of the City of Helsinki, Finland. The cohort was followed up using mail surveys in 2007 (N=7,332, response rate 83%) and 2012 (N=6,814, response rate 79%). For those consenting to external register linkage (74%), the data were linked to Finnish national administrative register data. The data on sickness absence benefits and reimbursed medication purchases were derived from The Social Insurance Institution of Finland and the data on disability retirement from the Finnish Centre of Pensions. The data on weight, height and covariates were collected through surveys. Statistical methods included repeated measures analysis, Cox proportional hazards models and negative binomial regression models. Overweight and obesity were generally unassociated with psychotropic medication, except for the association found between obesity and sedatives among men. Similarly, overweight and obesity were not associated with poor mental health functioning, even though the associations between obesity, weight gain and poor physical health functioning were strong. Weight gain among the normal-weight women and overweight men was associated with poor mental health functioning, but no association with changes over time were found. An association with sickness absence due to mental disorders was found among the weight-gaining and weight-maintaining obese women and weight-gaining overweight men. As regards disability retirement, the results suggested that among the women, overweight was independently associated with disability retirement due to any, musculoskeletal and mental diagnoses. Both obesity and weight gain were strongly associated with poor physical health functioning and work disability in general and work disability due to musculoskeletal diseases. However, the findings regarding the association between body weight and subsequent mental ill-health were weak and mainly non-existent, even though cross-sectional associations and synergistic effects between body weight and common mental disorders were found. From a public health perspective, it is important to prevent both overweight and mental ill-health at all levels and in all sectors of society. Primary and occupational health care should have resources to pay attention to weight gain and mental ill-health in their early stages.