Blood pressure is usually thought of as a cardiovascular concern, but maintaining a healthy blood pressure is one of the most important steps you can take to protect your brain. High blood pressure (hypertension) is a major risk factor for stroke and vascular dementia, a serious change in memory and thinking skills caused by reduced blood flow to the brain, usually the result of narrowing or blockages in the brain’s arteries.
Low blood pressure (hypotension) also can deprive your brain of a healthy flow of oxygenated, nutrient-rich blood, which can lead to memory and cognition troubles, as well as increased risks for fainting and falls. Low blood pressure can occur naturally or be the unintended result of aggressive anti-hypertensive treatment.
“Taking steps to control your blood pressure throughout your life is the prudent thing to do,” explains Jonathan Rosand, MD, co-founder and co-director of the Henry and Allison McCance Center for Brain Health at Massachusetts General Hospital.
Hypertension’s Consequences
Blood pressure is simply the force of blood flow against the inner walls of your arteries. Your blood pressure changes many times throughout the day and night, and as we age, average blood pressure tends to rise. Hypotension can also develop in older age, but high blood pressure is more common and poses a greater threat to the health of your brain.
Over time, high blood pressure injures the walls of your arteries, potentially weakening them in some areas and causing them to become stiffer and narrower. At their healthiest, arteries are flexible blood vessels, able to widen and constrict as conditions require. Uncontrolled or poorly treated hypertension can make that difficult, not just in the brain, but in the heart and anywhere else in the body.
“High blood pressure is a way we have of assessing the continuous damage that happens to the end organs: the heart, brain and kidneys,” Dr. Rosand says. “The blood vessel damage is incremental, but is often reversible.”
Unfortunately, you may not know where the damage has occurred until a medical crisis occurs. A weakened artery in the brain can burst, causing a hemorrhagic stroke and bleeding into brain tissue. A hemorrhagic stroke is less common, but often more serious than an ischemic stroke, which occurs when an artery supplying blood to the brain becomes blocked, halting the flow of blood and allowing brain cells to perish.
While a stroke is a dramatic medical emergency, there is another kind of impact hypertension can have on the brain that usually isn’t noticed until much of the damage has been done. High blood pressure can damage the smaller blood vessels in the parts of the brain responsible for thinking and memory.
Studies show that individuals with hypertension are more likely to have biomarkers of Alzheimer’s disease in their spinal fluid, and that people with widely fluctuating blood pressure have a higher risk of dementia later in life. Research also suggests that the risk of Alzheimer’s disease could be cut by as much as a third if people maintained healthy blood pressure throughout their lives, Dr. Rosand says.
Blood Pressure Targets
The American Heart Association defines normal or healthy blood pressure as less than 120/80 millimeters (mm) of mercury (Hg). The top number is the systolic pressure, the pressure in your arteries when your heart constricts and pushes blood through the arteries. The bottom number is the diastolic pressure, or the pressure in the arteries when the heart relaxes in between beats.
Elevated blood pressure is a systolic pressure of between 120 and 129 mmHg and a diastolic pressure of less than 80 mmHg. Stage 1 high blood pressure is defined as a systolic pressure of 130 to 139 mmHg and/or a diastolic pressure of 80 to 89 mmHg. Stage 2 is a systolic pressure of 140 or mmHg or higher and/or a diastolic pressure of 90 mmHg or higher.
Two years ago, the Systolic Blood Pressure Intervention Trial (SPRINT), supported by the National Heart, Lung, and Blood Institute, determined that keeping systolic pressure under 120 mmHg had numerous health benefits, including a lower risk of mild cognitive impairment (MCI), a precursor to dementia. An extension of the SPRINT MIND portion of the study is ongoing to further explore whether lowering blood pressure to under 120 mmHg can reduce dementia risk.
Dr. Rosand urges his patients to strive for a blood pressure that is under 120/80 mmHg, but he cautions that care is needed not to go too low. Working with your doctor on blood pressure management is key. “There are quite a few antihypertensive medications that are safe and effective,” he says. “You and your doctor can find a treatment that works for you. But you have to be careful.”
Hypotension’s Challenges
Aggressive blood pressure-lowering treatments can lead to hypotension, a condition that can cause weakness, dizziness, fatigue and fainting. A blood pressure reading of lower than 90/60 mmHg is generally considered to be hypotension, though some older adults can function without symptoms or complications with blood pressure that is consistently lower than 90/60 mmHg.
Drugs such as fludrocortisone, which boosts blood volume, can be helpful in treating low blood pressure. Another drug, midodrine, is also helpful in treating a condition called orthostatic hypotension. It occurs when you stand up and your blood pressure drops significantly.
Adding salt to your food and drinking more fluids are other ways to increase your blood pressure. And if you’re taking antihypertensive medications, you may need to adjust your dosage or try a different type of medication that won’t drive down your blood pressure quite so much.
Is It Too Late?
If you have not maintained a healthy blood pressure throughout your life, there is no reason not to get it under control starting today. Aside from lowering your risk of future blood vessel damage and the health consequences that can follow, keeping your blood pressure in a healthy range may allow your blood vessels to heal on their own and reverse some of that previous damage.
For people who have struggled to control their hypertension even after using three or more medications a condition known as resistant hypertension Dr. Rosand says the risks are too great to stop trying.
“The key is to not give up,” he says, adding that you may need to make tougher lifestyle choices to give your medications some help. “Reduce your intake of salt, exercise regularly, lose weight if necessary, reduce stress, try meditation it all can help.”
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