People over the age of 60 who are treated for their high blood pressure (hypertension) have a 26% lower risk of dementia compared to those who are untreated, according to research from UNSW Sydney's Centre for Healthy Brain Ageing (CHeBA).
The study, published in JAMA Network Open, highlighted that dementia risk was substantially reduced in the treated hypertension group throughout late life. The study is the largest of its kind to date, utilising data from 34,519 individuals across 15 different countries including Australia, USA, Brazil, China, Italy, Central African Republic and Nigeria.
Dementia poses a burgeoning worldwide challenge with approximately 57 million people currently living with dementia and an anticipated 153 million by the year 2050. Hypertension is the most prevalent risk factor for dementia, affecting more than 1 billion people worldwide.
Dr Matt Lennon, a medical doctor and lead author on the study, said the findings were critical for general practitioners and family physicians, who are most commonly at the coal face of blood pressure management.
We know that mid-life hypertension increases risk of all types of dementia by around 60%, and Alzheimer's disease by 25%.
Dr Matt Lennon
"However, in late-life (i.e. those older than 60) studies have variously found high blood pressure to increase, not affect or decrease dementia risk. This lack of clarity is deeply problematic."
Dr Lennon explained that in this study the international research team clarified ambiguities in the field using the power of big data from CHeBA's COSMIC collaboration (Cohort Studies of Memory in an International Consortium). The research also aimed to understand how age, sex and race might change the association between blood pressure, antihypertensive use and dementia.
A positive shift for public health
According to Dr Lennon, the findings will have an impact on blood pressure management guidelines and will change parts of the academic conversation around blood pressure.
"This study provides responses to critical questions for public health," says Dr Lennon.
Firstly, the study identified that in late life people with unmedicated hypertension have a significantly elevated risk of dementia compared to those with medicated hypertension and healthy individuals. This relationship was not significantly altered by increasing age, which shows that even people in their 70s and 80s are at lower risk of dementia if hypertension is treated.
This is a valuable addition to the literature as it crystallises a grey area in dementia prevention.
Dr Matt Lennon
Secondly, the study illustrated that a single measure of blood pressure in late-life was not associated with significant differences in dementia risk and the authors suggested that multiple measurements over time should be used to direct treatment.
Finally, the study indicates that there are no significant differences in the effect of blood pressure or antihypertensive use in different sexes or racial groups.
"This is a very promising result as it suggests that optimal care for one group will be similar for others," says Dr Lennon. "No study previously has been able to assess the differential effects of blood pressure and antihypertensives in developing nations.
"Our study included three major studies of ageing based in Nigeria and the Central African Republic. It is critical that an understanding of chronic illness management in the developing world is published and disseminated. It is precisely in these areas where chronic illnesses are least well understood but also where the majority of new dementia cases will occur in the coming decades."
Co-Director of CHeBA and co-author on the research, Professor Perminder Sachdev, said that "The findings indicate that ongoing antihypertensive therapy throughout late life is an important part of dementia prevention."
