Medical costs of obese Japanese: A 10-year follow-up study of National Health Insurance in Shiga, Japan

Koshi Nakamura, Tomonori Okamura, Hideyuki Kanda, Takehito Hayakawa, Akira Okayama, Hirotsugu Ueshima, Shigeo Yamashita, Yoshinori Tominaga, Kazuaki Katsuyama, Fumihiko Kakuno, Machiko Kitanishi, Yukio Tobita, Kanehiro Okamura, Kiminobu Hatta, Takao Okada, Michiko Hatanaka

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


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/m2), participants were classified into the following three categories: BMI < 18.5, 18.5 ≤ BMI < 25.0 and 25.0 ≤ BMI. Medical costs per person per month were compared among the three categories. Excess medical costs attributable to the 25.0 ≤ BMI category compared to the 18.5 ≤ 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 ≤ BMI < 25.0) and 155 Euros (25.0 ≤ 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 ≤ BMI category represented 3.1% of the total medical costs for the entire study population (634 105 Euros). Conclusion: 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.

Original languageEnglish
Pages (from-to)424-429
Number of pages6
JournalEuropean Journal of Public Health
Issue number5
Publication statusPublished - Oct 2007
Externally publishedYes


  • Body mass index
  • Japan
  • Medical costs
  • Obesity

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health


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