Purpose: Recent U.S. guidelines redefining blood-pressure categories have generated a continuing controversy regarding the new "prehypertensive" category (systolic, 120-139, diastolic, 80-89), signifying heightened risk of progression to outright hypertension and a need for lifestyle changes and frequent follow-up. This study addresses an incompletely-explored empirical question: how well does prehypertension predict an early transition to hypertension?
Methods: Blood-pressure and other longitudinal data obtained from two British Health and Lifestyle Surveys conducted 7 years apart were used to form a subsample of 2048 men and women normotensive at baseline. Prehypertension was divided into subcategories: "normal" (systolic, 120-129; diastolic, 80-85) and "high normal" (systolic, 130-139; diastolic, 85-89), with "optimal" (systolic, < 120; diastolic < 80) as reference. Binomial regression was used to estimate adjusted relative risks (RR) and confidence intervals (CI) for hypertension at follow-up. This is an appropriate method (and preferable to logistic regression) when the outcome is common.
Results: Estimated RR for the "normal" subcategory was 2.0 (CI, 1.6, 2.6) and for "high normals," 2.9 (CI, 2.3, 3.7). Separate regressions by age bracket showed the greatest risks for high normals aged 35 to 44 years.
Conclusions: The results support the hypothesized prehypertension effects, especially for younger high normals, but are more conservative than the Framingham-based estimates.