Hypertension with diabetes mellitus: significance from an epidemiological perspective for Japanese

The prevalence of both hypertension and diabetes mellitus is increasing worldwide. Both diseases lead to severe complications such as cardiovascular and chronic kidney diseases, which increase the risk of death over a long period of time. Therefore, the prevention and aggravation of hypertension and diabetes mellitus are major challenges. Because few review articles have focused on the epidemiological perspective of hypertension and diabetes mellitus, we reviewed major observational studies mainly from Japan and from Western countries that have reported on the prevalence of hypertension and diabetes mellitus, the binominal risk of hypertension and diabetes mellitus, and the risk of their coexistence. Our investigation found that approximately 50% of diabetic patients had hypertension, and approximately 20% of hypertensive patients had diabetes mellitus. Those with either hypertension or diabetes mellitus had a 1.5- to 2.0-fold higher risk of having both conditions. These results were similar for both Japan and Western countries. Although comparing the results between Japan and Western countries was difficult because the risks were estimated using widely varying statistical analyses, it was revealed that the coexistence of hypertension and diabetes mellitus certainly increased the risk of complications regardless of the country. The definition, prevalence and medical treatment of hypertension and diabetes mellitus will change in the future. For early intervention based on the latest evidence to prevent severe complications, it is important to accumulate epidemiological knowledge of hypertension and diabetes mellitus and to update the evidence for both Japan and other countries.