Blood Pressure and Your Brain
Last reviewed by Faculty of Harvard Medical School on January 24, 2013
By Harvey B. Simon, M.D.
High blood pressure is considered a cardiovascular disease because it involves the heart and blood vessels. High blood pressure (hypertension) is the leading cause of stroke. The higher your pressure, the higher your risk.
But since arteries are vital to the health of all our organs, hypertension is actually a threat to the whole body. Heart disease, heart failure and peripheral artery disease are among the dreadful results of untreated hypertension.
In many cases, hypertension's most damaging impact does not fall on the heart, but on the eyes, kidneys and especially the brain. It's increasingly clear that hypertension contributes to the risk of mild impairments in memory, thinking and judgment.
The good news is that treating hypertension protects your brain and your heart. If you cut your usual blood pressure by just three points, you'll reduce your risk of stroke by 8%.
High blood pressure doesn't only increase your risk of stroke. Although study results vary, the weight of evidence now suggests that high blood pressure takes a toll on the aging brain. It increases the risk of memory loss (mild cognitive impairment) and dementia (severe disturbances of memory, reasoning and judgment). There's even evidence that it adds to the risk of Alzheimer's disease.
Both systolic (top number) and diastolic (bottom number) hypertension contribute to the problem. In general, the higher the pressure and the longer it persists without treatment, the greater the risk of mental decline.
Most of these studies have focused on older adults. For example, a study of 2,505 men ages 71 to 93 reported that men with systolic pressures of 140 mm Hg or higher were 77% more likely to develop dementia than men with systolic pressures below 120 mm Hg. But a study that evaluated blood pressure and cognitive function in people ages 18 to 46 and 47 to 83 also found that high systolic and diastolic pressures were linked to cognitive decline over time in these age groups.
Since hypertension damages blood vessels, it's easy to see how it can contribute to a type of dementia called vascular dementia. This develops when small vessels in the brain become diseased or blocked. This deprives brain cells of the oxygen and sugar they need. If enough nerve cells are damaged or killed, memory can't be restored.
The link to Alzheimer's disease is less obvious. The problem begins with the accumulation of beta-amyloid, a small sticky protein that interferes with the function of nerve cells and eventually kills off cells, leaving a mass of tangles and plaques in its wake. In most cases, the part to the brain that is responsible for memory (the hippocampus) is hit the hardest. But new research suggests that vascular damage and tissue inflammation add to the injury.
Doctors may be able to help ease the burden of dementia, but the damage and disability cannot be reversed. That makes prevention doubly important.
European scientists reported that long-term therapy to treat high blood pressure reduced the risk of dementia by 55%. Several American studies have also shown positive results:
Even if you forget that hypertension is bad for your brain, remember that men with normal blood pressures live 5.1 years longer than men with hypertension.
Know your blood pressure. It seems obvious, but about 30% of people with hypertension don't know they have the disease. Be sure to have your pressure measured with each check-up and keep your own record so you can spot an upward trend as early as possible.
Know your goal. Even if you are just in the prehypertensive range (systolic pressure from 120 to 139 or diastolic pressure from 80 to 89), you should try to bring your pressure down to a normal reading below 120/80. People with hypertension can use somewhat less stringent targets. For otherwise healthy people, a reading below 140/90 is reasonable but for patients with diabetes, chronic kidney disease, coronary artery disease, or atherosclerosis, the goal is below 130/80.
Modify your lifestyle. If you have hypertension, it's essential to change your lifestyle. Because lower blood pressure is better for health, anyone with blood pressure above 115/70 can benefit from these changes:
Use medications if you need more help. A shocking 65% of patients with hypertension are above their target blood pressure numbers. Most experts recommend thiazide diuretics, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers and calcium-channel blockers as first-line drugs. New research suggests that another old stand-by, the beta-blockers, may be less effective for preventing strokes. Doctors often start with a thiazide diuretic, but depending on your particular needs, another drug may be best. Therapy with two or more drugs may be required.
Work with your doctor to do whatever is needed to get your blood pressure to where it belongs. It will take some thought and effort, but it's the brainy thing to do.
Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.