Can High Blood Pressure Increase Risk of Dementia and Alzheimer's?

High Blood Pressure Has Been Correlated with Dementia Risk
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If you know someone with Alzheimer's disease or another kind of dementia, you likely have wondered what causes this disease to develop, and if there's anything you can do to prevent it.

One area that's been discussed and debated for years now is high blood pressure. But, does high or low blood pressure really make a difference, or is this one of those issues that just generally improves your health but hasn't actually been connected to the risk of dementia?

What the Research Says

High blood pressure has long been viewed as a risk factor for vascular dementia. More recently, multiple studies have implicated high blood pressure as a risk factor for dementia in general—not limiting the risk to vascular dementia. Here are summaries of four of those studies:

High blood pressure was associated with mild cognitive impairment

One study included 918 participants that were assessed over an average period of 4.7 years. The researchers found that individuals with high blood pressure were more likely to develop mild cognitive impairment, a condition that often progresses to Alzheimer's disease. Interestingly, this study found that executive functioning impairment, one of the symptoms of mild cognitive impairment, was more likely than memory impairment, to develop with high blood pressure.

High blood pressure was related to the development of white matter lesions in the brain

A second study of 1424 women who underwent MRIs found that those with blood pressures over 140/90 at the start of the study were associated with significantly higher amounts of white matter brain lesions eight years later. The white matter lesions were most commonly located in the frontal lobes of the brains, and are associated with a higher risk of stroke and dementia.

High blood pressure in mid-life correlated with brain changes and a higher risk of dementia later

A third study found that high blood pressure in mid-life was related both to a higher risk of later life dementia and also correlated with changes in the amount of beta amyloid protein in the brain. The researchers found that those changes were present approximately 15 years before cognitive impairments developed, providing more evidence that prevention of dementia should be a focus long before old age.

Untreated high blood pressure was associated with brain changes typical to Alzheimer's disease

Finally, a fourth study found further evidence connecting blood pressure to cognition. This study used brain imaging to assess 118 cognitively intact participants ages 30-89 years. Researchers found that individuals with high blood pressure had accumulated more beta amyloid protein in their brains compared to those without high blood pressure, similar to the study above. (Accumulation of beta amyloid protein is one of the hallmarks of Alzheimer's disease.)

This study also distinguished between people who were being treated with medication to control their blood pressure and those who weren't. What they found is that the brains of people who were being treated for high blood pressure- not just those without high blood pressure- were protected from negative brain changes.

Is Lower Blood Pressure Always Better?

A couple of studies have been conducted to measure the rate of cognitive decline in people who have dementia, have lower blood pressure and are being treated with antihypertensive (blood pressure lowering) medications.The results showed that some people on these medications with a systolic blood pressure reading (the top number) of less than 128 experienced a faster cognitive decline than those whose blood pressure was higher.

This has called into question how and when antihypertensives are prescribed for adults over the age of 65, with some organizations recommending a separate set of guidelines for older adults who have a dementia diagnosis.

More research needs to be conducted in this area, as it's possible that other factors are influencing these results.

Next Steps

Being aware of this information is helpful, but what's next? Here are three practical action steps to take:

  1. Know your risk. If you aren't familiar with your blood pressure reading, get it checked regularly.
  2. Ask. If your blood pressure is high, ask your doctor about treating it.
  3. Prevent. Prevention in the younger and middle years of life appears to be extremely important in reducing your risk of dementia in the later years. Physical exercisemental activity and a healthy diet can make a difference in your current and future health and have all been associated with a decreased risk of developing dementia. It's never too late to begin a healthier lifestyle.

Sources:

High blood pressure and brain health are linked. American Heart Association. http://newsroom.heart.org/news/high-blood-pressure-and-brain-health-are-linked. 

Kuller LH, Margolis KL, Gaussoin SA, et al. Relationship of hypertension, blood pressure, and blood pressure control with white matter abnormalities in the women’s health initiative memory study (WHIMS)-MRI trial. The Journal of Clinical Hypertension. 2010;12(3):203–212. doi:10.1111/j.1751-7176.2009.00234.x

Mossello E. Low blood pressure and Antihypertensive drug use. JAMA Internal Medicine. 2015;175(4):578–585. doi:10.1001/jamainternmed.2014.8164. http://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2173093.

Reitz C, Tang M-X, Manly J, Mayeux R, Luchsinger JA. Hypertension and the risk of mild cognitive impairment. 64(12). http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2672564/.

Shah N, Vidal J, Masaki K, et al. Midlife blood pressure, plasma β-amyloid, and the risk for Alzheimer disease: The Honolulu Asia aging study. Hypertension (Dallas, Tex. : 1979). 2012;59(4):780–6. http://www.ncbi.nlm.nih.gov/pubmed/22392902. 

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