Assessment of Weight Change and All-Cause Mortality Based on Body Mass Index Intervals in South Korea: A 12-Year Follow-Up of the Korean Longitudinal Study of Aging

Background: Obesity and weight loss are associated with increased mortality. Understanding the association between weight change and mortality is critical and can help inform effective prevention and intervention strategies. Therefore, this study aimed to investigate the association between weight change and mortality based on body mass index (BMI) intervals using data from a 12-year follow-up survey in Korea.Methods: We used data from the Korean Longitudinal Study of Aging from 2006 to 2018. Individuals aged 45–69 years without a history of malignancy and chronic obstructive pulmonary disease at baseline were selected. Cox regression analysis was used to compare mortality based on body mass index and weight change.Results: Compared with individuals with a body mass index of 20.0–25.0 kg/m2 and an increase in body weight of <5 kg, mortality was 3.8 times higher in the group with a body mass index of <20.0 kg/m2 and a weight loss of <5 kg, two times higher in the group with a body mass index of 20.0–25.0 kg/m2 and weight loss of >10 kg, and 4.3 times higher in the group with a body mass index of ≥25.0 kg/m2 and weight gain of ≥10 kg. Conclusions: Weight loss in underweight or normal-weight individuals and weight gain in individuals with obesity increased the mortality rate compared with individuals with normal weight and less weight change. This suggests that body weight and the changes in the weight of individuals are crucial, and weight loss in patients with underweight and weight gain in patients with obesity are closely related to increased mortality.