Independent effects of stable and changing body weight on total mortality

Most studies find that associations between mortality and either body mass index or weight change are U-shaped. Previous studies, however, have not considered independent effects of weight level and weight change while also controlling for confounding by diseases leading to weight change. We used follow-up data on average 10-year total mortality from a Danish population of 15,113 men and women, who had their weight measured at about 5 year intervals. We obtained information on preexisting disease at surveys and by linkage to hospital discharge registers. We defined subclinical disease as incident disease or death during the first 4 years of follow-up. We decomposed the mortality risk associated with weight change into a static effect, corresponding to the difference in mortality at stable weight at the initial and attained weight, and a dynamic effect, estimated as the difference between mortality after weight change and mortality at stable weight at the attained weight. Both weight level and weight change had independent effects on total mortality, with both these associations being U-shaped. Adjustment for smoking and the exclusion of subjects with preexisting and subclinical disease did not alter the associations.