A blood pressure reading that is greater than 140 mmHg and left untreated will significantly worsen cognitive decline in older persons. However, systolic blood pressure that is lower than 120 mmHg and is treated with antihypertensive medications may also increase cognitive decline, according to new research from the Centre for Healthy Brain Ageing (CHeBA) at UNSW Sydney.

The study, published in The Journal of Gerontology: Medical Sciences, is important given the 2017 changes to blood pressure management guidelines that recommended blood pressure should be maintained below 120/80mmHg.

Dr Matt Lennon, a medical doctor and lead author on the study, said “Medical practitioners are being advised in people older than 70 that systolic blood pressure should be kept below 120 mmHg. Our study indicated that participants using antihypertensives with that blood pressure reading ended up with worsened cognitive decline.

“Over the course of our study they had approximately doubled the rate of cognitive decline compared to the average participant,” said Dr Lennon. 

“We also found that participants with blood pressure greater than 140 mmHg who did not use antihypertensives had similar worsened rates of cognitive decline, approximately double the average participant over the course of the study.

The research compared the cognitive outcomes of 1015 people from the Sydney Memory and Ageing Study aged 70-90 in three distinct systolic blood pressure groups. It was conducted over a 6-year period.

Dementia is the second leading cause of death in Australia and the single greatest cause of disability in older Australians (aged 65 years and older) and the third leading cause of disability burden overall.  In 2020 there is an estimated 459,000 Australians living with dementia and without a medical breakthrough, the number is expected to increase to over one million people by the middle of the century. 

Co-Director of CHeBA and author on the paper, Professor Perminder Sachdev, said that ongoing treatment at new recommendations of lower systolic blood pressure targets should be considered carefully in older populations. 

“High blood pressure is one of the most prevalent risk factors for dementia, affecting 1 in 4 adults and one billion people worldwide,” said Professor Sachdev.

“Maintaining blood pressure at appropriate levels through all stages in life must be part of the prevention strategy if we are to mitigate the effects of dementia on our society in the future.”

Dr Lennon said that it is important for patients and their families to know what their ideal blood pressure is for their age and to be aware of damaging cognitive effects of blood pressure that is too high or too low.