. Variation in blood pressure and long-term risk of dementia: A population-based cohort study. PLoS Med. 2019 Nov;16(11):e1002933. Epub 2019 Nov 12 PubMed.

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  1. Ma and colleagues have published an impressive study which examines the relationship between visit-to-visit blood-pressure changes and incident dementia. The results of this study highlight the importance of examining longitudinal blood pressure characteristics to understand how blood pressure may be associated with dementia risk.

    The finding that larger increases in blood pressure were associated with greater risk of dementia, especially if blood pressure changes occurred 15+ years before the period of dementia assessment, supports the recent results from the British Birth Cohort Study, which found that increases in blood pressure during early adulthood were associated with greater white-matter-hyperintensity volumes and lower brain volumes decades later (Lane et al., 2019). However, the current study extends previous findings by also showing that declines in blood pressure are associated with incident dementia, even when dementia is assessed many years later. These findings in particular are in line with results from our recent study within the Atherosclerosis Risks in Communities (ARIC) cohort, which demonstrated that older adults who showed a substantial (25 percent) decline in blood pressure after a period of chronic hypertension had an increased risk of subsequently developing mild cognitive impairment and dementia (Walker et al., 2019). 

    Although a number of studies have found a link between late-life declines in blood pressure and dementia risk, what had remained unclear was whether these drops in blood pressure only occur concurrently with cognitive decline, presumably as a result of neurodegenerative changes. By demonstrating that blood-pressure declines occurring a decade or more before the follow-up period are associated with dementia risk, the current study provides temporal evidence that blood pressure declines may actually be a risk factor for (and not simply an associated feature of) dementia.

    At the individual (patient) level, these findings provide support for the idea that large changes in blood pressure over just a few years in time might be worthy of additional attention, especially when occurring in adults over age 50. Although it is possible that large and frequent fluctuations in blood pressure have direct deleterious effects on brain health, in many cases, large variations in blood pressure may occur as a result of an underlying condition that itself may act as a more direct driver of dementia risk. This notion is supported by results from the current study showing that greater blood pressure variation is more strongly associated with dementia risk in patients with arterial stiffness. Arterial stiffness itself has been linked to several adverse neurocognitive outcomes, including elevated cortical amyloid, as was recently demonstrated in a study by Hughes and colleagues (Hughes et al., 2018).

    A number of other age-related conditions (e.g., physical frailty) may be jointly associated with increased blood pressure variability and dementia risk. It is likely that effective interventions for dementia prevention will come from strategies that target these underlying chronic conditions, which are known to cause steep changes in blood pressure.

    References:

    . Associations between blood pressure across adulthood and late-life brain structure and pathology in the neuroscience substudy of the 1946 British birth cohort (Insight 46): an epidemiological study. Lancet Neurol. 2019 Oct;18(10):942-952. Epub 2019 Aug 20 PubMed.

    . Association of Midlife to Late-Life Blood Pressure Patterns With Incident Dementia. JAMA. 2019 Aug 13;322(6):535-545. PubMed.

    . Arterial stiffness and dementia pathology: Atherosclerosis Risk in Communities (ARIC)-PET Study. Neurology. 2018 Apr 3;90(14):e1248-e1256. Epub 2018 Mar 16 PubMed.

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