Objectives: Few studies have focused on weight change and frailty, especially in Asia. This research aimed to evaluate midlife body mass index (BMI) trajectory and assess its relationship with frailty 8 years later in Taiwan.
Design: A prospective cohort study.
Setting and participants: Data were retrieved from the Taiwan Longitudinal Study on Aging conducted from 1999 to 2007. The analysis was restricted to respondents aged between 50 to 69 years old, who were not frail in 1999 and were alive in 2007 (n=1609).
Measurements: Frailty was defined using the Fried criteria. The group-based model of trajectory was used to estimate BMI trajectories among elderly participants. Logistic regression analysis was used to examine the association between BMI change and frailty.
Results: Four trajectory classes were identified and each remained stable during the 8-year follow-up. There were 316 participants (20.3%) in the low-normal weight group (baseline BMI=20.38 kg/m2), 737 participants (44.7%) in the high-normal weight group (baseline BMI=23.22 kg/m2), 449 participants (28.4%) in the overweight group (baseline BMI=26.24 kg/m2), and 107 participants (6.6%) in the obesity group (baseline BMI=30.65 kg/m2). After adjustment for confounding factors, the low-normal weight group and obesity group were associated with increased frailty compared with the high-normal weight group.
Conclusion: Our results showed that the BMI trajectories of midlife individuals tended to be constant and those in both the low-normal weight group and obesity group had an increased risk of developing frailty in later life. Therefore, an optimal weight-targeting strategy should be considered for Asian elderly individuals.
Keywords: body mass index; frailty; obesity; trajectory.