Prehypertension and the risk for cardiovascular disease in the Japanese general population: the Jichi Medical School Cohort Study.

Background: Prehypertension is associated with an increased risk of the development of hypertension and subsequent cardiovascular disease. However, it is unclear whether the increased risk of cardiovascular disease associated with prehypertension varies by duration of follow-up (i.e., the first 5 years vs. second 5 years) or varies between nonelderly and elderly individuals.

Methods: We enrolled 11,000 community dwelling persons (6739 women and 4261 men, aged 18-90 years) from the Japanese general population, followed them for an average of 10.7 +/- 2.4 years (117,517 person-years) and evaluated the incidence of cardiovascular events (including both stroke and myocardial infarction).

Results: In the full cohort, prehypertension was associated with a 45% higher risk of cardiovascular events than normal blood pressure after adjusting for traditional cardiovascular risk factors (hazard ratio = 1.45, P = 0.03). The risk of cardiovascular events with prehypertension during the second 5-year period was elevated in the nonelderly subgroup (<65 years) (hazard ratio = 2.13, P = 0.01), but not in the elderly subgroup (>or=65 years) (hazard ratio = 0.93, P = 0.82) (P = 0.054 for the difference in hazard ratio). The elevated risk with prehypertension during the first 5-year period was not significant in either the nonelderly (hazard ratio = 1.60, P = 0.36) or elderly (hazard ratio = 1.19, P = 0.63) group. However, the risks with prehypertension were not statistically different between the first and second 5-year period.

Conclusion: Prehypertension is associated with an increased 10-year risk of cardiovascular disease; the provocative finding that this risk may be especially elevated during the second 5-year period in the nonelderly requires confirmation in a larger cohort.