The predictive ability of blood pressure in elderly trial patients.
J Hypertens. 2012 Sep;30(9):1725-33. doi: 10.1097/HJH.0b013e3283568a73. Carr MJ, Bao Y, Pan J, Cruickshank K, McNamee R. Biostatistics, Health Methodology Research Group, University of Manchester, Manchester, UK.
OBJECTIVES: To assess the impact of the blood pressure (BP) profile on cardiovascular risk in the Medical Research Council (UK) elderly trial; investigate whether the effects of hypertensive drugs in reducing event rates are solely a product of systolic pressure reduction.
METHODS: Using longitudinal BP data from 4396 hypertensive patients, the general trend over time was estimated using a first-stage multilevel model. We then investigated how BP acted alongside other BP-related covariates in a second-stage 'time-to-event' statistical model, assessing risk for stroke events and coronary heart disease (CHD). Differences in outcome prediction between diuretic, β-blocker and placebo treatment arms were investigated.
RESULTS: The β-blocker arm experienced comparatively poor control of current SBP, episodic peaks and variability in BP levels. After adjusting for the mean level, variability in SBP over time was significant: risk ratio was 1.15 [95% confidence interval (CI): 1.01-1.31] across all patients for stroke events. The risk ratio for current SBP was 1.36 (95% CI: 1.16-1.58). Current DBP and variability in DBP also predicted stroke independently: risk ratios was 1.43 and 1.18, respectively. The risk factors exhibited weaker associations with CHD risk; only the highest measured value and variability in SBP showed a statistically significant association: risk ratios were 1.26 and 1.16, respectively.
CONCLUSION: Individual risk characterization could be augmented with additional prognostic information, besides current SBP, including current diastolic pressure, temporal variability over and above general trends and historical measurements.