Medical costs of obese Japanese: a 10-year follow-up study of National Health Insurance in Shiga, Japan.
BACKGROUND
For the Japanese population, a body mass index (BMI) of 25.0-29.9 is classified as obesity and is a risk factor for cardiovascular disorders such as hypertension.


METHODS
A cohort study to clarify obesity costs for a Japanese population was conducted utilizing baseline BMI and medical costs over a 10-year follow-up period. The participants were 4502 community dwelling Japanese National Health Insurance (NHI) beneficiaries aged 40-69 years. According to their baseline BMI values (kg/m(2)), participants were classified into the following three categories: BMI < 18.5, 18.5 < or = BMI < 25.0 and 25.0 < or = BMI. Medical costs per person per month were compared among the three categories. Excess medical costs attributable to the 25.0 < or = BMI category compared to the 18.5 < or = BMI < 25.0 category were estimated.


RESULTS
Approximately 20% of the Japanese population studied had a BMI of 25.0 or over. A J-shaped relationship between BMI and personal total medical costs was observed. Personal total medical costs per month determined from the 10-year follow-up in each category were 189 Euros (BMI < 18.5), 134 Euros (18.5 < or = BMI < 25.0) and 155 Euros (25.0 < or = BMI). A J-shaped pattern was observed after adjusting for age, sex, smoking and drinking habits, and excluding early deceased participants. Furthermore, smoking habit did not modify the J-shaped pattern of total medical costs. The estimated excess medical costs for the 25.0 < or = BMI category represented 3.1% of the total medical costs for the entire study population (634 105 Euros).


CONCLUSIONS
The Japanese NHI beneficiaries with a BMI of 25.0 or over showed increased medical costs compared to those with a BMI of 18.5-24.9.
Nakamura
Koshi
K
Department of Health Science, Shiga University of Medical Science, Otsu City, Shiga, Japan. ksnkmr@belle.shiga-med.ac.jp
Okamura
Tomonori
T
Kanda
Hideyuki
H
Hayakawa
Takehito
T
Okayama
Akira
A
Ueshima
Hirotsugu
H
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000209:etiology; D002423:Cause of Death; D003920:Diabetes Mellitus / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D017048:Health Care Costs / Q000706:statistics & numerical data*; D006801:Humans; D006937:Hypercholesterolemia / Q000209:etiology; D006973:Hypertension / Q000209:etiology; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009313:National Health Programs / Q000191:economics; D009765:Obesity / Q000191:economics* / Q000453:epidemiology* / Q000503:physiopathology; D011159:Population Surveillance; D016016:Proportional Hazards Models; D012307:Risk Factors; D012309:Risk-Taking