Is blood pressure variability associated with an increased risk of dementia?

Last year, Lancet commissioned a review on modifiable risk factors for dementia and reported that mid-life hypertension (systolic blood pressure > 140 mmHg) may be associated with a 60% increased risk of dementia [1]. In addition, a randomized controlled trial, the SPRINT-MIND study, suggested that aggressive blood pressure control (keeping systolic blood pressure below 120 mmHg) in individuals over the age of 50 reduced the risk of mild cognitive impairment, a precursor to Alzheimer’s disease [2]. However, one aspect of blood pressure control that is less well studied is whether blood pressure variability may be associated with an increased risk of dementia.

Epidemiology studies suggest that visit-to-visit blood pressure variability in a clinical setting may be associated with an increased risk of several adverse outcomes such as heart and kidney disease, stroke, and death [3]. Several epidemiology studies also suggest that visit-to-visit blood pressure variability may be associated with an increased risk of cognitive decline or dementia [3]. However, the field is still in its infancy, and most of these studies have been relatively short in duration. For instance, one reported that visit-to-visit blood pressure variability was associated with cognitive decline over six years but was not associated with the risk of dementia [4].

One study sought to examine the long-term impact of blood pressure variability on the risk for dementia. The investigators enrolled 5,273 individuals (average age of 68) without dementia and followed them for 15 years. Every two to four years, blood pressure measurements were taken twice in the clinic and the results were averaged. At each visit, the investigators also assessed whether the individual had developed dementia. They found that greater visit-to-visit blood pressure variability was associated with a significantly increased risk of dementia 5-15 years later. Both large increases and large decreases in blood pressure were associated with an increased dementia risk. This was true in those who were on antihypertensive medications and those who were not, suggesting that starting an antihypertensive therapy midway through the study did not account for the association between decreased blood pressure and dementia risk [5].

How might blood pressure variability increase the risk of dementia? The exact mechanisms are currently unknown, but several hypotheses have been suggested. Blood flow in the brain is tightly regulated. Exposure to wide swings in blood pressure may impair the ability of the brain to regulate blood flow which could lead to vascular or cellular damage. In addition, it was also reported that increased blood pressure variability may be associated with increased inflammation in blood vessels which may be damaging [3].

However, epidemiology studies do not show cause and effect, and it is still not clear that blood pressure variability can cause dementia. For instance, pathological brain changes may occur more than a decade before cognitive symptoms, and subtle damage to the brain in areas that control blood pressure may lead to increases in blood pressure variability. In addition, other factors that are associated with increased blood pressure variability, such as smoking, poor diet, poor sleep quality, and less physical activity, may also be associated with an increased risk of dementia. Future studies will shed light on the relationship between blood pressure variability and dementia risk. In addition, randomized controlled trials may provide information on whether specific antihypertensive drugs are more effective at reducing blood pressure variability than others [3].

Although easy to measure at home, blood pressure can vary during the time of day, in different settings, and if it is not taken correctly. Therefore, don’t be stressed if your blood pressure sometimes changes with different home measurements. However, the studies on blood pressure variability and its association with dementia support the maxim “what is good for the heart is good for the brain”, and there are several good ways to start improving your heart and brain health such as managing hypertension, exercising, and eating a healthy diet.

1. Livingston G, Huntley J, Sommerlad A et al. (2020) Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet  396, 413-446.
2. Group SMIftSR, Williamson JD, Pajewski NM et al. (2019) Effect of Intensive vs Standard Blood Pressure Control on Probable Dementia: A Randomized Clinical Trial. JAMA  321, 553-561.
3. Ma Y, Tully PJ, Hofman A et al. (2020) Blood Pressure Variability and Dementia: A State-of-the-Art Review. Am J Hypertens  33, 1059-1066.
4. van Middelaar T, van Dalen JW, van Gool WA et al. (2018) Visit-To-Visit Blood Pressure Variability and the Risk of Dementia in Older People. J Alzheimers Dis  62, 727-735.
5. Ma Y, Wolters FJ, Chibnik LB et al. (2019) Variation in blood pressure and long-term risk of dementia: A population-based cohort study. PLoS Med  16, e1002933.

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