Objective: To establish whether initiation of treatment with diuretic or β blocker is associated over 54 months with change in cognitive function.

Design: A cognitive substudy, nested within a randomised, placebo controlled, single blind trial.

Setting: 226 general practices from the Medical Research Council's general practice research framework.

Subjects: A subset of 2584 subjects sequentially recruited from among the 4396 participants aged 65-74 in the trial of treatment of hypertension in older adults. The 4396 subjects were randomised to receive diuretic, β blocker, or placebo. Subjects had mean systolic pressures of 160-209 mm Hg and mean diastolic pressures <115 mm Hg during an eight week run in.

Outcome measures: The rate of change in paired associate learning test (PALT) and trail making test part A (TMT) scores (administered at entry and at 1, 9, 21, and 54 months) over time.

Results: There was no difference in the mean learning test coefficients (rate of change of score over time) between the three treatments: diuretic -0.31 (95% confidence interval -0.23 to -0.39), β blocker -0.33 (-0.25 to -0.41), placebo -0.30, (-0.24 to -0.36). There was also no difference in the mean trail making coefficients (rate of change in time taken to complete over time) between the three groups: diuretic -2.73 (95% confidence interval -3.57 to -1.88), β blocker -2.08 (-3.29 to -0.87), placebo -3.01, (-3.69 to -2.32). A less conservative protocol analysis confirmed this negative finding.

Conclusion: Treating moderate hypertension in older people is unlikely to influence, for better or for worse, subsequent cognitive function.

• Key messages
• Studies have shown that treating hypertension in older adults reduces cardiovascular mortality and morbidity
• Treating moderate hypertension with either diuretic or β blocker does not seem to influence cognitive function
• Concerns about damaging cognition should not deter doctors from treating hypertension in older patients
• Age should no longer be a factor in the decision to initiate antihypertensive treatment