What is an ideal blood pressure? Recommendations from 2003 categorized a systolic blood pressure of <130mmHg as normal, 130-140mmHg as borderline, and >140mmHg as hypertensive. However, new guidelines published in 2017 by the American College of Cardiology (ACC) and the American Heart Association (AHA) lowered that bar. The ACC/AHA guidelines consider <120mmHg as normal, 120-130mmHG as elevated, and >130mmHg as hypertensive. New evidence released this year suggest that these guidelines may be appropriate when considering midlife hypertension and the risk of future dementia.
A recent observational study from France looked at blood pressure in individuals at age 50, 60, and 70 to see if high blood pressure increased the risk of dementia at late-life. They found that patients at age 50 who had a systolic blood pressure greater than 130mmHg had a 38% increased risk of dementia and those with a systolic blood pressure greater than 140mmHg had a 30% increased risk of dementia. Interestingly, hypertension at age 60 and 70 did not increase the risk of dementia later in life .
Observational studies cannot determine cause and effect. However, this study is supported by results from a randomized controlled trial announced at the 2018 Alzheimer's Association International Conference. The Systolic Blood Pressure Intervention Trial (SPRINT) enrolled patients over 50 years of age with a systolic blood pressure of 130-180mmHg. Patients were randomized to either intensive hypertension treatment (a systolic blood pressure target of 120mmHg or lower) or standard hypertension treatment (a systolic blood pressure target of 140mmHg or lower). The trial was stopped early because intensive blood pressure treatment had a clear benefit for preventing cardiovascular disease . However, the participants were followed for an additional three years to determine whether intensive hypertension treatment reduced the risk of dementia. Intensive hypertension treatment did not significantly reduce the risk of dementia; however, it did reduce the risk of mild cognitive impairment (MCI), which is often a precursor to dementia, by 17%.
Why didn't intensive treatment reduce the risk of dementia? It could be that the trial did not run long enough. Patients were as young as 50 years old, and a longer trial might be able to determine whether intensive hypertension treatment really reduced the risk of dementia. Also, patients were only intensively treated for a few years before the trial was stopped. It is also important to note though that lowering your blood pressure too much may increase your risk of side effects. Patients in the intensive treatment were more likely to experience hypotension (low blood pressure), syncope (temporary loss of consciousness due to low blood pressure), electrolyte abnormalities, and acute kidney injury.
Managing chronic illness is important for brain health. A report from The Lancet Commission suggested that 2% of all cases of dementia can be prevented with proper blood pressure control . The ACA/AHA guidelines stressed the importance of monitoring hypertension in those under 45 years of age since hypertension is expected to increase among men and women. Milder forms of hypertension may be treated by proper diet (e.g. the DASH diet), increased physical activity, and reduced alcohol consumption. Greater levels of hypertension may need to be treated with one or more types of anti-hypertensive medications. Remember, healthy habits in your 40s and 50s can potentially reduce your risk of dementia later in life.
Nick McKeehan is Assistant Director, Aging and Alzheimer's Prevention at the Alzheimer’s Drug Discovery Foundation. He served as Chief Intern at Mid Atlantic Bio Angels (MABA) and was a research technician at Albert Einstein College of Medicine investigating repair capabilities of the brain. He received a bachelor of science degree in biology from Purdue University, where he was awarded a Howard Hughes Scholarship. Mr. McKeehan also writes about the biotechnology industry for 1st Pitch Life Science.
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