Impact of smoking habit on medical care use and its costs: a prospective observation of National Health Insurance beneficiaries in Japan

Background To quantify excess medical use associated with smoking, a large prospective cohort study is needed. The authors examined the impact of smok ing on medical care use in a large population-based cohort with an accurate data collecting system in Japan. Method The data were derived from a 30-month prospective cohort study of 43 408 National Health Insurance beneficiaries aged 40-79 years living in a r ural Japanese community. The smoking habit of beneficiaries was assessed in a baseline survey at the end of 1994. Medical care use and its costs were monitored by linkage with the National Health Insurance claim history files since January 1995. Results Male smokers incurred 11% more medical costs (after adjustment for age, physical functioning status, alcohol consumption, body mass index and average time spent walking) than 'never smokers' but for female smokers and never smokers the costs were almost the same. This difference was mainly a ttributable to increased use of inpatient medical care among smokers, espec ially in males, where per month cost of inpatient care was 33% higher in sm okers. Age-group specific analysis in men showed that excess mortality and excess medical cost ratio for smokers peaked in those aged 60-69 years. Conclusions Smokers consume excess medical care. Among the population aged 45 years and over, about 4% of total medical costs were attributable to smo king. To pursue both better health and lower medical costs for the nation, a comprehensive programme to reduce tobacco use is needed.