In the call for papers (Alley DE, Ferrucci L, Barbagallo M, Studenski SA, Harris TB. A research agenda: the changing relationship between body weight and health in aging. J Gerontol A Biol Sci Med Sci. 2008;63(11):1257-1259.), it is assumed that the association between body mass index (BMI [kilogram per square meter]) and mortality becomes increasingly U-shaped with advancing age. The aim of this study is to examine the association between BMI and mortality and to test whether the association is changing with advancing age for persons aged 70-95 years in Denmark. The study populations comprised two surveys: the Longitudinal Study of Aging of Danish Twins (LSADT) and the Danish 1905 Cohort Survey. From 1995 to 1999, 4253 individuals aged 70-95 years from the LSADT were interviewed at home. In 1998, 2,262 individuals aged 92-93 years from the 1905 Cohort were interviewed at home. The information in both surveys included self-reported weight and height. With virtually no loss to follow-up, survival was assessed through a 10-year follow-up period, during which 4,664 (72%) of the persons died. The association between BMI and mortality is changing with advancing age for people aged 70-95 years. There was a significant decrease in the association between mortality and low BMI with advancing age for both genders (p < or = .03). There was also a tendency for the association between mortality and high BMI to decrease with advancing age for males (p = .06). In a large contemporary Danish population-based sample, the association of BMI and mortality became decreasingly U-shaped with advancing age for the age range 70-95 years.
