The effects of blood pressure reduction on cognitive function: a review of effects based on pooled data from clinical trials

Objective To review systematically and synthesize quantitatively the evidence from completed randomized, controlled trials of blood pressure reduction on cognitive performance. Methods MEDLINE, EMBASE and Cochrane databases were searched to identify randomized, controlled trials that measured the effect of blood pressure reduction on cognitive performance. Additional studies were identified by searching bibliographies of retrieved articles and contacting experts in the field. Data were extracted on study quality, blood pressure, performance on cognitive function tests, antihypertensive treatment regimens and the duration of treatment. Studies were reviewed and abstracted independently by two trained researchers. Results Sixteen studies with 19 501 subjects were identified. Modest reductions in blood pressure (< 5/3 mmHg) in 13 860 subjects were associated with improvements in Mini Mental State Examination score [ weighted mean difference (WMD) = 0.19; 95% confidence interval (CI) = 0.19 - 0.19] and performance on immediate (WMD = 0.62; 95% CI = 0.21 - 1.02) and delayed (WMD = 0.67; 95% CI = 0.23 - 1.11) logical memory tasks. However, studies in 2380 subjects that included tests of perceptual processing and learning capacity (trail making test-A, paired associated learning test) showed impaired performance (WMD = -1.12 s; 95% CI = -1.22 to -1.02 and WMD = -0.04; 95% CI = -0.04 to -0.04) on these tests. Conclusion Blood pressure lowering may have a heterogeneous effect on different aspects of cognitive function. Future studies with specific cognitive end- points are needed for greater clarity to guide practice.