High incidence of colorectal cancer in Japanese individuals with hypertension.

The association between hypertension and the incidence of colorectal cancer remains controversial. This study aimed to clarify this relationship in a Japanese population using two large-scale cohort datasets. We conducted a population-based retrospective cohort study using the Shizuoka Kokuho Database, which contains insurance claims from the Shizuoka region and medical checkup data collected between 2012 and 2022. Propensity score matching was used to compare colorectal cancer incidence between normotensive and hypertensive groups, and cumulative incidence was analyzed using Gray's test, with death treated as a competing risk. Among individuals not taking antihypertensive medications, the normotensive and hypertensive group included 113,724 and 85,399 individuals, respectively. During the follow-up period (median, 4.38 years), colorectal cancer developed in 1130 individuals in the normotensive group and 850 in the hypertensive group. After propensity score matching, colorectal cancer incidence was significantly higher in the hypertensive group, with a hazard ratio of 1.15 (95% confidence interval, 1.02-1.30). This association was observed in men. Among individuals taking antihypertensive medications, an increased risk of colorectal cancer was observed in women. To evaluate whether genetically determined susceptibility to hypertension influences colorectal cancer incidence, we additionally analyzed polygenic risk score for blood pressure using a separate Japanese prospective cohort (Japan Multi-Institutional Collaborative Cohort). No positive association between polygenic risk score for blood pressure and colorectal cancer incidence was identified. This discordance between epidemiological findings and genetic analysis warrants careful interpretation, including, but not limited to, the possibility of previously unrecognized environmental factors shared by colorectal cancer and hypertension.