A Cochrane review included 4studies with a total of 15,936 subjects with hypertension. Average age was 75.4 years and mean blood pressure at entry was 171/86 mmHg. No studies included patients with dementia or with previous cerebrovascular accident. Planned mean length of study follow-up was 5 years in all trials. In one trial dementia was diagnosed by the DSM-III-R criteria. In 3 other trials Mini Mental State Examination (MMSE) was evaluated at follow-up visits and decline of MMSE points under 23-24 or by reduction of 3-4 points were used as triggers for further diagnostic evaluation for dementia.There was no difference in the incidence of dementia between treatment and placebo groups (236/7767 versus 259/7660, Odds Ratio (OR) = 0.89, 95% CI 0.74 to 1.07). There was no benefit from treatment as evaluated by change in MMSE (Weighted Mean Difference (WMD) = 0.42, 95% CI 0.30 to 0.53; 3 trials, 13504 patients). Both systolic and diastolic blood pressure levels were reduced significantly (WMD = -10.22, 95% CI -10.78 to -9.66 for systolic blood pressure, WMD = -4.28, 95% CI -4.58 to -3.98 for diastolic blood pressure).
Comment: The quality of evidence is downgraded by indirectness ( the percentage of patients taking initially assigned medication alone was 25-30% and the number of placebo patients given active treatment was 27-84% in trials).