Persona-based stratification and XGBoost modeling for multi-dimensional vehicle sound quality evaluation.

The global population aged 75 years and older has been increasing rapidly, leading to a substantial rise in healthcare expenditure. Therefore, the extension of healthy life expectancy and prevention of chronic diseases have become important public health priorities. Compared with younger adults, older adults exhibit distinct metabolic characteristics, including age-related changes in body composition, increased comorbidity burden, and reduced physiological resilience. Emerging evidence suggests that body weight variability is more closely associated with adverse health outcomes than single body mass index (BMI) measurements. Weight variability, representing long-term dynamic changes in body weight, can result from intentional or unintentional causes. Weight variability independent of the mean (VIM) has been proposed as a quantitative index of body weight fluctuation and has been associated with increased risk of cardiovascular disease, dementia, all-cause mortality. However, most previous studies were conducted either in disease-specific cohorts or in general populations encompassing a wide range of ages, whereas in older adults, weight variability more often reflects unintentional changes due to underlying diseases, frailty, or medication use. With increasing prevalence of obesity and growing interest in weight management in older adults, obesity‑related metabolic and functional risks, particularly in the setting of age‑related muscle loss, underscore the importance of understanding the health implications of body weight fluctuation. Despite the growing clinical relevance, large-scale studies analyzing the relationship between weight variability and mortality in older adult populations remain limited. Therefore, this study aimed to evaluate the association between long-term weight variability, assessed by VIM, and the risk of all-cause and cause-specific mortality in a large, nationwide cohort of individuals aged ≥ 75 years, and to assess whether weight variability itself has an independent effect on mortality risk regardless of the direction of weight change.