Background: body mass index is used widely to define overweight and obesity. Both high and low body mass indices are associated with increased mortality risk during middle age, but the relationship is less clear in later life. Thus, studies on the relationships between other aspects of body composition and mortality among older subjects are needed.
Objective: to investigate associations between different aspects of body composition and mortality in older people.
Methods: the study population comprised 921 participants aged ≥65 years who underwent dual-energy X-ray (DXA) absorptiometric examination at the Sports Medicine Unit, Umeå University. The main reason for admission was clinical suspicion of osteoporosis. Total, abdominal and gynoid fat masses and lean body mass were measured by DXA absorptiometry at baseline, and the cohort was followed (mean duration, 9.2 years) for mortality events.
Results: during follow-up, 397 participants died. Lean mass was associated negatively with mortality in men and women (P < 0.001). Total fat mass showed a U-shaped association with mortality in men (P < 0.01) and a negative association in women (P < 0.01). A higher ratio of abdominal to gynoid fat mass increased mortality risk in women (P = 0.04), but not in men (P = 0.91).
Conclusions: lean mass is associated strongly with survival in older subjects. Greater fat mass is protective in older women, whereas very low or very high fat mass increases the risk of death in men. Further research is needed to better understand the mechanisms underlying these associations.