title: Blood pressure lowering in patients without prior cerebrovascular disease for prevention of cognitive impairment and dementia.
abstract: BACKGROUND
  This is an update of a previous review (McGuinness 2006).Hypertension and cognitive impairment are prevalent in older people. Hypertension is a direct risk factor for vascular dementia (VaD) and recent studies have suggested hypertension impacts upon prevalence of Alzheimer's disease (AD). Therefore does treatment of hypertension prevent cognitive decline?
  
  
  OBJECTIVE
  To assess the effects of blood pressure lowering treatments for the prevention of dementia and cognitive decline in patients with hypertension but no history of cerebrovascular disease.
  
  
  METHODS
  The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS as well as many trials databases and grey literature sources were searched on 13 February 2008 using the terms: hypertens$ OR anti-hypertens$.
  
  
  METHODS
  Randomized, double-blind, placebo controlled trials in which pharmacological or non-pharmacological interventions to lower blood pressure were given for at least six months.
  
  
  METHODS
  Two independent reviewers assessed trial quality and extracted data. The following outcomes were assessed: incidence of dementia, cognitive change from baseline, blood pressure level, incidence and severity of side effects and quality of life.
  
  
  RESULTS
  Four trials including 15,936 hypertensive subjects were identified. Average age was 75.4 years. Mean blood pressure at entry across the studies was 171/86 mmHg. The combined result of the four trials reporting incidence of dementia indicated no significant difference between treatment and placebo (236/7767 versus 259/7660, Odds Ratio (OR) = 0.89, 95% CI 0.74, 1.07) and there was considerable heterogeneity between the trials. The combined results from the three trials reporting change in Mini Mental State Examination (MMSE) did not indicate a benefit from treatment (Weighted Mean Difference (WMD) = 0.42, 95% CI 0.30, 0.53). Both systolic and diastolic blood pressure levels were reduced significantly in the three trials assessing this outcome (WMD = -10.22, 95% CI -10.78, -9.66 for systolic blood pressure, WMD = -4.28, 95% CI -4.58, -3.98 for diastolic blood pressure). Three trials reported adverse effects requiring discontinuation of treatment and the combined results indicated no significant difference (OR = 1.01, 95% CI 0.92, 1.11). When analysed separately, however, more patients on placebo in Syst Eur 1997 were likely to discontinue treatment due to side effects; the converse was true in SHEP 1991. Quality of life data could not be analysed in the four studies. Analysis of the included studies in this review was problematic as many of the control subjects received antihypertensive treatment because their blood pressures exceeded pre-set values. In most cases the study became a comparison between the study drug against a usual antihypertensive regimen.
  
  
  CONCLUSIONS
  There is no convincing evidence from the trials identified that blood pressure lowering in late-life prevents the development of dementia or cognitive impairment in hypertensive patients with no apparent prior cerebrovascular disease. There were significant problems identified with analysing the data, however, due to the number of patients lost to follow-up and the number of placebo patients who received active treatment. This introduced bias. More robust results may be obtained by conducting a meta-analysis using individual patient data.
authors.affiliation: Department of Geriatric Medicine, Queen's University Belfast, Whitla Medical Building, 97 Lisburn Road, Belfast, UK, BT9 7BL.
authors.forename: Bernadette
authors.initials: B
authors.lastname: McGuinness
authors.forename: Stephen
authors.initials: S
authors.lastname: Todd
authors.forename: Peter
authors.initials: P
authors.lastname: Passmore
authors.forename: Roger
authors.initials: R
authors.lastname: Bullock
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000517:prevention & control*; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D003072:Cognition Disorders / Q000517:prevention & control*; D015140:Dementia, Vascular / Q000517:prevention & control*; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000188:drug therapy*; D016032:Randomized Controlled Trials as Topic
chemical_list: D000959:Antihypertensive Agents