Blood pressure and dementia risk – the evidence
Hypertension is a risk factor for cerebrovascular disease and vascular dementia. Hypertension in midlife is also associated with an increased risk of Alzheimer’s disease. Blood pressure may decline in the preclinical stage of Alzheimer's and low blood pressure later in life may be associated with increased risk [1].
Treatment of hypertension in old age has been identified in several studies to reduce the risk of cognitive decline and dementia. In a 4 year study of 2,400 patients, treatment reduced the risk of dementia by 55% [2].
Studies assessing long term use of antihypertensives from midlife show a cumulative reduction in risk of dementia for each year of treatment [1,3]. A study that followed hypertensive men from midlife found that for each additional year of treatment there was a further reduction in the risk of dementia [3].
Those treated for more than 12 years had a 60% reduced risk of any dementia and 65% reduced risk of Alzheimer's disease compared to those never treated.The risk after 12 years of treatment was similar to those with normal blood pressure.
How does blood pressure impact on dementia risk?
Hypertension may contribute to both cerebrovascular pathology and Alzheimer's disease pathology [4]. Hypertension may lead to endothelial dysfunction, microinfarcts and cerebral ischaemia. Endothelial changes could also affect microvascular clearance of beta amyloid and exacerbate Alzheimer’s disease pathology.
References
- Haag MD, et al. Duration of antihypertensive drug use and risk of dementia. A prospective cohort study. Neurology, 2009, 72:1727-1734.
- Forette F, et al. The prevention of dementia with antihypertensive treatment. New Evidence from the Systolic Hypertension in Europe (Syst-Eur) study. Arch Intern Med, 2002, 162:2046-2052.
- Peila R, et al. Reducing the risk of dementia. Efficacy of long-term treatment of hypertension. Stroke, 2006, 37:1165-1170.
- Knopman DS. Hypertension and late-life dementia. A real link? Neurology, 2009, 72:1716-1717.
