High blood pressure, or hypertension, affects 17.5% of Canadians over the age of 12 and 1 in every 3 American adults however, the rates are not the same for everyone with elderly adults over the age of 65 being most affected. Hypertension is known to be a risk factor for a number of other conditions including: heart failure, stroke and heart attack, vision loss, and kidney disease. Blood pressure raises with age and can also be elevated in people who smoke, who drink, or have diabetes or obesity. We often have our average blood pressure measured by doctors to understand if our hypertension is under control. Normal blood pressure is anything less than 120/80 but this number can vary based on your gender, ethnicity, and age. Our blood does not stay constant from day to day though, it varies depending on what you have eaten, time of day, how hydrated you are, stress, and many other factors. What is still currently under-appreciated is how the daily variation in our blood pressure may affect our health. Now researchers from New Jersey have found out that the day to day variations in blood pressure can affect the ability of the elderly to think and process information.
The researchers collected blood pressure and cognitive function data on about 970 Chinese elderly adults who had been part of another study. They grouped the adults into three groups of around 300 people each based on how variable their blood pressure was from clinic visit to clinic visit. Blood pressure consists of two measurements: 1) the systolic pressure, which is the pressure in the arteries when the heart is contracting and 2) the diastolic pressure, which is the pressure in the arteries when the heart is relaxed. They found that adults who had higher visit to visit variation in their systolic blood pressure (number on top ie. 120) had a faster decline in cognitive function and verbal memory. These were measured by determining the participant’s ability to count backwards from 20, recalling words from a list, recall the date, orientation of objects, and ability to recall commonly used household items. Additionally, a greater variation in the diastolic blood pressure (bottom number ie. 80) was also associated with a decrease in cognitive function. These results were all independent of any changes in the average blood pressure of each person, that is to say, they were only related to how variable a person’s blood pressure was not to their actual blood pressure.
Other research has suggested that there is higher visit to visit variability in blood pressure measurements in people with Alzheimer’s and dementia. It is thought that variations in blood pressure could cause temporary poor blood flow to parts of the brain resulting in damage to that region. It is also possible that variations in blood pressure could results in damage to the small vessels of the brain resulting in small brain bleeds. Still more work needs to be done to determine the exact relationship between variable blood pressure and potential brain damage. There are some limitations to this study, 1) some potential variables that affect blood pressure were not available to the researchers (depression, heart rate, etc.) and these may affect the results; and 2) The blood pressure was only measured at clinic visits so we don’t know as much about the actual day to day variation in blood pressure which could be greater than they measured in this study. Still, this research sheds more light on the importance of not only getting your blood pressure down to a reasonable level but also in making sure it doesn’t fluctuate too greatly. It also draws an important link between blood pressure and the health of your brain.