Hypertension occurs when the blood is under increased pressure,pushing against the walls of your blood vessels. Systolic pressure,the top number of a blood pressure reading, measures the pressureduring a heart beat. The bottom number, the diastolic pressure,measures the pressure between heart beats. A normal blood pressureis defined as 120/80 or lower. Blood pressure between 120 to140/80 to 90 is "pre-hypertension" and any thing over 140/90is definite hypertension.
The number of adults in the United States with high blood pressure(hypertension) has increased 30% over the last decade. At least65 million people (one-third of adults) in America suffer fromhypertension. Hypertension does not usually cause symptoms,so many adults who have hypertension may not even be aware ofit. When left untreated, hypertension can lead to coronary heartdisease, heart failure, stroke, kidney failure, and other problemssuch as memory loss. More information about memory loss canbe found on the next page.
How can hypertension cause memory loss and other problems?
Hypertension can cause damage to blood vessels by causing abuild-up inside the blood vessels, making them narrow. Thisrestricts the amount of blood that can flow through them. Ifthe narrowed blood vessel becomes blocked such that no bloodcan get through, this can lead to a heart attack or a stroke.Even reduced blood flow to the brain can have damaging effects.The brain must have a certain amount of blood flow to work normally.About one quart of blood normally flows through the brain everyminute. If the amount of blood flow is less than it should be,the brain cannot work efficiently. This can lead to memory lossand other symptoms.
In this issue of Neurology, Jennings and colleagues1 evaluatethe effects of hypertension on blood flow to parts of the braininvolved in memory. They studied 37 people with hypertensionand 59 people with normal blood pressure. Two types of memorywere tested in these study participants: spatial and verbalmemory. Spatial memory was measured by asking participants toremember the position of items seen on a computer screen. Verbalmemory was measured by asking participants to remember words.While participants were performing these memory tests, the bloodflow through the brain was measured using a brain scan calledpositron emission tomography (PET). PET allows researchers todetermine which parts of the brain are most active during atask, because active areas receive increased blood flow.
The researchers found that when people with hypertension performmemory tasks, they have less blood flow to parts of the braininvolved in memory and more blood flow to other brain regionsthan people with normal blood pressure. Despite the differencesin blood flow, the performance on the memory tests was the samein both groups. The investigators believe that this is becausethe hypertensive group was able to compensate for the decreasedblood flow to the memory areas of the brain by increasing bloodflow to other areas. It is possible that this ability to compensatecan only go so far. Increasing damage to the brain blood vesselscaused by untreated hypertension could eventually lead to memoryloss because non-memory areas of the brain are not able to keepup.
The differences in blood flow between people with hypertensionand people with normal blood pressure may explain why peoplewith hypertension may develop memory problems. It is importantfor all adults to have blood pressure checked regularly to preventmany serious health problems. If your blood pressure is consistentlyhigh, you should talk with your doctor about the best treatmentfor you.
Memory is a person’s ability to remember information.It is commonly divided into three major types: short-term, long-term,and working memory. Short-term memory is a person’s abilityto remember new information. For example, when directory assistancegives us a telephone number, we may forget it before we tryto dial it. Long-term memory refers to the ability to rememberthings that were learned in the past. For example, some peoplehave problems remembering the name of a person they have notseen for a long time. Short-term memory is affected more byaging than long-term memory.
Working memory involves doing two things at once. Studies showthis type of memory is also affected by aging. For example,think about trying to subtract two big numbers in your head.You need to hold the numbers in your memory at the same timethat you are making computations involving "borrowing." Whenyou focus on the subtraction process, you may forget the originalnumbers you were working with. This seems to create a drainon your memory capacity, or a kind of overload.
Although problems with memory become increasingly common aspeople age, most people never develop severe memory problemsor dementia unless they have a disease or injury. Some of theseinclude Alzheimer disease, head injury, seizures, alcoholism,brain infections or tumors, and stroke; certain medicationscan also cause memory loss. Another reason may be simple disuse.The table lists common reasons why people have trouble rememberingthings.
Research shows that many things affect how well people remember,at any age. If you know what they are, you can use this informationto help your own memory functions. For example, when you areupset, you cannot concentrate well and so may not "learn" whatyou ultimately want to remember. Sometimes it seems that a person’smemory is not working well, but the real reason is that theperson is distracted. For example, if you enter a room to getsomething and the telephone rings, you may forget why you wentinto the room.
When you do not pay attention, you are not likely to registerinformation in the first place. Paying attention takes effort.Think of the times you rush out the door, forgetting something.Perhaps you need to slow down and pause. For example, do youever wonder whether you have already done something, such asturning the oven off or turning the light out in the basement?To increase your ability to remember, you need to pay attentionto what you are doing, so that it will register in your memory.
In one study, researchers found that people were less likelyto develop dementia if they participated in some type of leisuretime activity. The chances of developing dementia got lowerwith each additional activity a person participated in. To loweryour chances of developing severe memory loss, the more activitiesyou are involved in throughout your life, the lower your riskmay be. This suggests that just as with physical health, a healthymemory requires you to use it or lose it!
What should I do if I am concerned about my memory?
If you or your family is concerned that you may have a memoryproblem, you should talk to your physician. It is importantto write down examples of the problems you are having. It isalso important to take a friend or family member with you tothe appointment to help provide information to the doctor thatyou may not remember.
Jennings JR, Muldoon MF, Ryan C, et al. Reduced cerebral blood flow response and compensation among patients with untreated hypertension. 2005;64:1358–1365.
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