Treated and untreated hypertension, hospitalization, and medical expenditure: an epidemiological study in 314 622 beneficiaries of the medical insurance system in Japan

Objective: This study investigated the effect of hypertension on hospitalization risk and medical expenditure according to treatment status in a Japanese population. Methods: A total of 314 622 beneficiaries of the medical insurance system in Japan, aged 40-69 years, without a history of cardiovascular, cerebrovascular, or end-stage renal disease were classified into seven blood pressure categories. These categories were used to compare the risk of undergoing hospitalization in the 1 year after the baseline survey and to examine the percentage of inpatient medical expenditure attributable to overall hypertension relative to total medical expenditure in the study population. Results: During the follow-up period, 6.6% of men and 5.1% of women were hospitalized. In men and women aged 40-54 years, cases of hypertension, especially grade 3 untreated hypertension, led to more frequent hospitalization, compared with optimal blood pressure. Individuals who were hospitalized, especially long-term, incurred considerably higher medical expenditure compared with those who were not hospitalized, regardless of their hypertension status. In women aged 55-69 years, there was little variation in hospitalization risk across blood pressure categories. The inpatient medical expenditure attributable to overall hypertension represented 7.2 and 6.9% of the total medical expenditure for men aged 40-54 and 55-69 years, whereas it represented 2.8 and 3.8% for women, respectively. Conclusion: Although cases of hypertension were an economic burden especially in men, grade 3 untreated hypertension was more likely to incur extremely high medical expenditure as a result of hospitalization, compared with other cases.