Key result
Estimated risk for late-life dementia for every 1-SD decrease in midlife plasma Aβ was higher for individuals with diastolic BP ≥90 mm Hg compared to those with diastolic BP ≤80 mm Hg.
Why the study?
Is midlife blood pressure and plasma amyloid-β associated with the risk of late-life Alzheimer disease and vascular dementia in Japanese-American men?
Is midlife blood pressure and plasma amyloid-β associated with the risk of late-life Alzheimer disease and vascular dementia in Japanese-American men?
This editorial highlights that midlife diastolic hypertension interacts with lower plasma amyloid-β levels to increase the risk of late-life Alzheimer's disease.
T he association between hypertension and vascular de- mentia (VaD) is well established and biologically plausible.Hypertension and small vessel disease are common in vascular cognitive impairment. 1 The relatively more recent discovery that hypertension is associated with increased risk of Alzheimer disease (AD) is less intuitively understandable, and so the search for mechanisms continues.Recognizing that sensitivity may be preferred to specificity in the early stages of seeking to identify plausible mechanisms, the report by Shah et al 2 in this issue of Hypertension takes an important step in this direction.Using a prospective design, these investigators examined the association between midlife blood pressure (BP) and amyloid- (A) peptide levels and risk for late-life AD and VaD in 667 Japanese-American men participating in the Honolulu Asia Aging Study.Data for the analyses were taken from 7 examinations, Ϸ3 years apart beginning between 1965 and 1967 and ending in 2000.The outcome measures were prevalent and incident AD (with and without contributing cardiovascular disease), pure AD (nϭ38), and VaD (nϭ24).Cerebral amyloid angiopathy (CAA), A neuritic plaques, and neurofibrillary tangles were evaluated postmortem in a subsample of 73 men.Midlife BP was not associated with prevalence or incidence of VaD.However, for the all-AD outcome category there was an interaction between diastolic BP and plasma A measures for prevalent AD.Estimated risk for late-life dementia for every 1-SD decrease in plasma A at midlife was higher for diastolic hypertensive individuals (BP Ն90 mm Hg) than for persons with low diastolic BP (Յ80 mm Hg) for both A1-40 and A1-42 assays.For the smaller pure AD group this same result was obtained when the A1-40 but not when the A1-42 assay was used, although the trend was in the same direction for both assays.This finding is biologically plausible.As Shah et al 2 make clear in the rationale for their study, A peptides are neurotoxic and promote vasoconstriction and cerebral vascular pathology, and when lower values of A are seen in plasma, higher
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Elias et al. (2012) conducted an editorial in Alzheimer Disease and Vascular Dementia (n=667). Midlife blood pressure and plasma amyloid-β levels vs. Low diastolic BP (≤80 mm Hg) was evaluated on Prevalent and incident Alzheimer disease and vascular dementia. Estimated risk for late-life dementia for every 1-SD decrease in midlife plasma Aβ was higher for individuals with diastolic BP ≥90 mm Hg compared to those with diastolic BP ≤80 mm Hg.
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