Factors Associated with Weight Loss in a National Longitudinal Study among Community-Dwelling Individuals 45 Years and Older in Thailand in 2015-2022

Introduction: : Only a small number of research has evaluated the determinants of weight loss among ageing adults in poorly resourced countries. Thus, using longitudinal and nationally representative community-dwelling data from 2015 to 2022 in Thailand, also stratified by sex, this study sought to examine the factors associated with weight loss among those 45 and older. Methods: Four waves of Health, Ageing, and Retirement in Thailand (HART) investigations were analyzed in 2015, 2017, 2020, and 2022 (analytical baseline sample N=2775). Weight loss (>5kg in the past 12 months) was assessed by self-report. The time-variant factors and outcomes were evaluated using conditional fixed-effects logistic regression. Results: Regressions found that increasing age (AOR = 1.07, 95% CI: 1.03-1.07, p < 0.001), transitioning to not working (AOR = 1.47, 95% CI: 1.10-1.96, p = 0.009), decreasing economic status (AOR = 0.94, 95% CI: 0.89-0.99, p = 0.035), an increase in hospitalisation (AOR = 1.58, 95% CI: 1.22-2.04, p < 0.001), an increase in multimorbidity (AOR = 1.42, 95% CI: 1.01-2.00, p = 0.043), an increase in functional disability (AOR = 1.52, 95% CI: 1.28-1.81, p < 0.001), an increase in wearing dentures (AOR = 1.66, 95% CI: 1.07-2.58, p = 0.025), increasing depressive symptoms (AOR = 1.06, 95% CI: 1.02-1.10, p < 0.001), and increasing social participation (AOR = 1.32, 95% CI: 1.01-1.71, p = 0.041) were significantly associated with weight loss. In addition, among men, transitioning to living alone (AOR = 2.12, 95% CI: 1.23-3.66, p = 0.009) was associated with increased weight loss. Conclusion: This long-term study improves our knowledge of the factors that contribute to weight loss in people 45 years of age and older. We found that health and psychosocial factors were associated with weight loss. The early detection and management of these identified associated factors may be important for preventing weight loss, especially among underweight older adults in Thailand.