Medical costs attributable to obesity and obesity-related health disorders in a Japanese population using JMDC claims...

This study aimed to estimate the medical costs attributable to obesity among Japanese adults with obesity-related health disorders using the JMDC claims database and assess the impact of body mass index (BMI) categories on the medical costs during a five-year follow-up period.

A retrospective cohort study using anonymized claims and health checkup data from the JMDC database was conducted. Participants aged ≥18 years with first recorded BMI between December 2012 and December 2018 and diagnosed with obesity-related health disorders were included. Participants were stratified into two groups: those without obesity (BMI <25.0 kg/m²) and those with obesity (BMI ≥25.0 kg/m²). Annual medical costs (total, outpatient, inpatient, medication) were summarized. Generalized estimating equations (GEE) with a gamma regression model and log link function were used to estimate cost ratios and adjusted mean total medical costs, adjusting for age category, sex, baseline BMI category, and baseline outpatient visit frequency. Sensitivity analyses were performed to assess robustness across different age groups and regression models.

A total of 244,150 eligible participants were analyzed (without obesity: 150,217; with obesity: 93,933). Over five-year follow-up, total medical costs per person-year increased from 218,929 to 265,919 JPY in those without obesity and from 234,093 to 323,086 JPY in those with obesity. Higher baseline BMI showed greater five-year increases in the adjusted medical costs, resulting in 27.7% increase by excess costs due to obesity with 83.3% of those attributable to BMI ≥27.0 kg/m². Sensitivity analyses confirmed the robustness of these findings.

The estimated excess costs due to obesity indicate higher healthcare costs among Japanese adults with obesity-related health disorders. The per capita burden appeared higher in those with higher BMI, with most excess costs concentrated in individuals with BMI ≥27.0 kg/m². These results highlight the healthcare cost burden associated with obesity and suggest that effective weight management strategies may contribute to reducing healthcare expenditures.