Bodyweight increase since early adulthood as a risk factor for mobility decline: a 7-year longitudinal study of 10,316 Japanese adults aged ≥ 40 years

Bodyweight increase since early adulthood is a risk factor for lifestyle-related diseases and may be a predictor of mobility decline. Locomotive syndrome (LS) is a condition characterized by reduced mobility due to musculoskeletal impairments, and its severity reflects the degree of mobility decline. This study aimed to investigate the association between a bodyweight increase of ≥ 10 kg since age 20 and the progression of LS severity. This was a 7-year longitudinal observational study including 10,316 Japanese adults aged ≥ 40 years who underwent health checkups in 2016 and 2023. Total bodyweight increase from age 20 to baseline was self-reported. Based on established cut-off values, LS severity was assessed using the 25-question Geriatric Locomotive Function Scale (GLFS-25), the two-step test, the stand-up test, and total assessment according to predefined criteria. LS progression was defined as a worsening by at least one LS severity category from 2016 to 2023; all others, including those with persistently non-LS status, were classified as non-progression. A multivariate logistic regression analysis was performed to examine associations, adjusting for potential confounders. Considering age-related weight changes in older adults, a sensitivity analysis was performed, restricted to participants aged 40–65 years (n = 9994). The mean age of the participants was 50.0 years (range, 40–84 years), and 4044 (39.2%) were female. Of the 10,316 participants, 3530 (34.2%) showed an increase in body weight from age 20 to baseline of ≥ 10 kg. A bodyweight increase of ≥ 10 kg was significantly associated with the progression of LS severity assessed by the GLFS-25 (odds ratio [OR]: 1.38, 95% confidence interval [CI]: 1.11–1.71), the stand-up test (OR: 1.20, 95% CI: 1.00–1.45), and the total assessment (OR: 1.23, 95% CI: 1.05–1.44), but not by the two-step test (OR: 0.99, 95% CI: 0.70–1.42). The sensitivity analysis results were generally consistent, indicating the robustness of our findings. A bodyweight increase of ≥ 10 kg since early adulthood was associated with the progression of LS severity assessed by the GLFS-25, the stand-up test, and the total assessment. Therefore, midlife weight management is crucial to preventing mobility decline at older age.