Psychological impact of body mass index changes in older adults: a 12-year longitudinal study

Significant changes in body mass index (BMI) may be associated with psychological distress, particularly in older adults. However, few longitudinal studies have examined this relationship over time. This study aimed to investigate the association between BMI changes and psychological distress assessed repeatedly among community-dwelling older adults in Taiwan.

This 12-year prospective cohort study included 70,570 adults aged ≥ 65 years who participated in the Taipei City Government's annual physical examination program between 2005 and 2016. BMI changes were classified relative to baseline (Definition 1) and prior follow-up measurements (Definition 2). Psychological distress was assessed using the Brief Symptom Rating Scale (BSRS-5). Multivariable generalized estimating equation (GEE) models were used to evaluate associations between BMI changes and psychological distress. Sensitivity analyses included a Cox proportional-hazards model treating incident psychological distress (first BSRS-5 ≥ 6) as the outcome, with BMI change as a time-varying covariate, and a lagged model relating BMI change to distress at the subsequent examination.

Under both definitions, participants with major weight loss (> 10%) had the highest risk of psychological distress (Definition 1: adjusted odds ratio [aOR] = 1.90, 95% confidence interval [CI]: 1.77-2.04; Definition 2: aOR = 1.96, 95% CI: 1.80-2.14). Minor weight loss (5%-10%) also increased the risk (Definition 1: aOR = 1.60, 95% CI: 1.52-1.68; Definition 2: aOR = 1.52, 95% CI: 1.44-1.60). Minor and major weight gains were associated with elevated but comparatively lower risks. In sensitivity analyses, the association between weight loss and psychological distress remained significant and dose-dependent, although attenuated; associations with weight gain were not robust.

Weight loss was consistently and dose-dependently associated with psychological distress in older adults and may serve as an early marker of declining health. Regular monitoring of weight change, rather than static weight status, may help prompt timely mental-health screening and nutritional or psychosocial assessment in this population.