A study across 20 countries has strengthened a link between lowering blood pressure, and reducing the risk of dementia.
The meta-analysis, published in the European Heart Journal, draws on clinical trial data from 28,008 participants, to show the strongest link to date between medication that lowers blood pressure, and reduced dementia risk.
“We know that high blood pressure is a risk factor for dementia – especially high blood pressure in midlife, so say 40 to 65 years of age,” says lead author Dr Ruth Peters, an associate professor at the University of New South Wales and program lead for dementia in the George Institute’s Global Brain Health Initiative.
“But there has been some uncertainty about whether lowering blood pressure, especially in older adults, would reduce risk of dementia.
“What we’ve done is take five really high-quality clinical trials and combine them into one dataset, which gave us the ability to really look at this question and look at the relationship between blood pressure-lowering tablets – antihypertensives – and dementia.”
The five studies were all double-blind, randomised clinical trials – the ‘gold standard’ in medical research – with participants hailing from 20 different countries.
The average age of the participants was 69, and participants were followed up an average of four years after doing the trial.
Participants who took antihypertensives had a significantly lower chance of being diagnosed with dementia than those who took placebos.
Dementia affects 50 million people worldwide: a number projected to triple by 2050.
According to The Lancet’s 2020 Commission on dementia, treatment for hypertension (high blood pressure) is “the only known effective preventive medication for dementia,” all other methods of reducing your risk come from lifestyle and environment.
“The strength of this study is the use of individual patient data in a meta-analysis of data drawn from randomised controlled trials of blood pressure medication. This is the first time such data has been meta-analysed,” says Professor Kaarin Anstey, a senior principal research scientist at Neuroscience Research Australia and the UNSW.
“This is important for informing clinical practice,” adds Anstey, who was not involved with the study.
Professor Nicolas Cherbuin, head of the Australian National University’s Centre for Research on Ageing, Health and Wellbeing, says that the study is “well-designed”, and reflects research by his team showing that higher blood pressure is linked to lower brain volumes and poorer brain health.
“The diagnostic procedure and criteria used are well-established, the sample size is large, those with dementia at baseline were excluded,” says Cherbuin.
But he points out that the study didn’t find an effect of blood pressure medication on cognitive decline, and nor did it include participants with mild cognitive impairment, who would be “more likely to convert”.
Anstey points out that “inevitably” the participants in the cohort are now quite old, and thus may be different to populations developing dementia now.
“Clinical trials involve highly selected samples and often exclude diverse ethnic groups,” she adds.
“I hope that this reinforces the importance of blood pressure control for brain health,” says Peters.
But she emphasises that, while this is useful news for preventing dementia in mid-life, people of all ages can improve their brain health by other means.
“It’s not just blood pressure lowering – it has to be taken in the context of a healthy lifestyle.”
Cosmos, 26 October 2022