Epidemiologic Studies of Psychosocial Factors Associated With Quality of Life Among Patients With Chronic Diseases in Japan

A link between affective disturbances and physical disorders has been suggested since the Greco–Roman era. However, evidence supporting an association between mind and body is limited and mostly comes from North America and Europe. Additional local epidemiologic studies are needed so that more evidence can be collected on effective treatments and health management. Epidemiologic studies of Japanese with rheumatoid arthritis (RA) and those on chronic hemodialysis examined the association between psychosocial factors and patient quality of life (QOL). Strong associations among depression, social support, and patient QOL were confirmed, which supports the findings of studies performed in Western countries. In addition, disparities between the perspectives of patients with RA and their doctors were observed. Alexithymia, a personality construct that reflects a deficit in the cognitive processing of emotion, had a stronger independent association with increased risk of 5-year mortality than did depression among patients with chronic hemodialysis. Physiological, biological, and psychosocial factors are associated and independently and interactively determine our health. Epidemiology is a powerful tool for identifying effective points of intervention, after considering all possible confounders. Future studies must clarify how health can be improved by using a psychosocial approach.