Joint impact of health risks on health care charges: 7-Year follow-up of National Health Insurance beneficiaries in Japan (the Ohsaki Study)

Background. The objective of this study was to examine the joint impact of modifiable health-risk factors such as smoking, obesity, and physical inactivity on direct health care charges. Method. We conducted a population-based prospective cohort study, with follow-up from 1995 to 2001. The participants were Japanese National Health Insurance (NHI) beneficiaries (26,110 men and women aged 40-79 years). Results. 'No risk' group defined as never-smoking, body mass index (BMI) 20.0-24.9 kg/m², and walking for ≥1 h/day had mean health care charges of $171.6 after adjustment for potential confounders. Compared with this group, the presence of smoking (SM; ever-smoking) alone, obesity alone (OB; BMI ≥25.0 kg/m²), or physical inactivity (PI; walking for <1 h/day) alone were associated with a 8.3%, 7.1%, or 8.0% increase in health care charges, respectively. The combinations of the risks of SM and OB, SM and PI, OB and PI, and SM and OB and PI were associated with a 11.7%, 31.4%, 16.4%, and 42.6% increase in charges, respectively. Conclusion. Interventions to improve modifiable health-risk factors may be a cost-effective approach for reducing health care charges as well as improving people's health.