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Emerging evidence shows significant links between untreated hypertension and the development of dementia.
Hypertension is ubiquitous, being the most frequently seen condition in Australian general practice, and in 2022 approximately 6.8 million Australians (one-third of all adults) lived with high blood pressure. It is estimated that of those with hypertension, 50% are undiagnosed, 18% are diagnosed but their condition is uncontrolled and only 32% are diagnosed, treated and have adequate control. Those over the age of 65 have the highest rates of previous hypertension diagnosis (34%) but also the most poorly controlled blood pressure (39% have measured high blood pressure). Concerningly, it may be that blood pressure control is getting worse, with rates of elevated blood pressure in the community screening increasing from 21.5% in 2011–12 to 23.3% in 2022.
But why is hypertension so drastically underdiagnosed and undertreated?
The multiple reasons include that it is largely asymptomatic, highly variable on measurement and its association with adverse outcome is variable and temporally distant. Additionally, antiquated clinical perspectives persist that high blood pressure is “normal” or even healthy in old age. Understanding of the risks of hypertension remains poor in the general population. Although clinicians and patients often know that it is associated with heart disease and strokes, there is little public understanding of the emerging evidence of high blood pressure as a risk factor for dementia. Our teams based at the Centre for Healthy Brain Ageing and the George Institute, University of New South Wales, have been exploring this relationship.
New evidence on the relationship between hypertension and dementia
In 2019, we published a meta-analysis that showed a clear relationship between mid-life hypertension and Alzheimer’s dementia (AD), with stage 1 (> 140 mmHg SBP) and stage 2 (> 160 mmHg SBP) hypertension associated with an 18% and 25% increased AD risk, respectively. Similarly, a 2020 meta-analysis reported that mid-life hypertension was associated with a 19–55% increased risk of all-cause dementia. However, for hypertension in late-life, longitudinal studies had indicated a mixture of positive, negative and null associations, with no clear effect of hypertension on dementia risk.
In 2023 and 2024, our group published two individual-participant data (IPD) meta-analyses examining all-cause dementia (referred to as dementia) and AD as outcomes respectively. The studies included 34 519 participants over the age of 60 (mean age [standard deviation, SD] = 72.5 [7.5]) from 15 countries. We found that individuals with untreated hypertension had a greater risk of both dementia (+42%) and AD (+36%) compared to those without a previous diagnosis of hypertension. More interestingly, individuals with treated hypertension had no significantly elevated risk of either dementia or AD compared to those with no previous diagnosis and the treated individuals had a substantially lower risk than those who were left untreated (-26% and -42% respectively). These results were not moderated by increasing age, indicating that there were substantial risk differences between the treated and untreated groups, even for individuals in their 70s and 80s. In our meta-analysis, we found that a single measure of blood pressure in late-life had no significant association with dementia risk, suggesting that more than one blood pressure measurement may be needed in older patients for accurate risk stratification.
Our meta-analyses included participants from Nigeria, the Republic of Congo and Central African Republic, who are populations that have been historically under-represented in research. We found that there were no significant moderating effects of race or sex, suggesting that effective treatments for one group are likely to be similarly effective for others.
Our studies have some clear limitations but the most challenging is the fact that they are observational in nature and are therefore likely to be confounded by non-random differences between the treated and untreated groups. Notwithstanding this challenge, our results are consistent with recent clinical trial results and systematic reviews. A 2022 meta-analysis of 5 randomised control trials of late-life participants found that antihypertensive use resulted in a 13% reduced risk of dementia and the 2024 Lancet commission report found that hypertension increases dementia risk by 20%.
Considered as a whole, the evidence strongly indicates that ongoing antihypertensive use in late-life is a critical part of dementia prevention in Australia and around the world.
The path forward: informing the public of risk and improving rates of blood pressure control
In a recent survey of Australians attending an outpatient clinic, dementia was the second most feared disease, having been listed as the primary worry for 29.3% of respondents, compared to only 7.3% and 3.7% who replied with “coronary heart disease” and “cerebrovascular disease” respectively. The now strong evidence base connecting high blood pressure and dementia will change the way that patients see blood pressure and may modify the way they think about risk of non-detection and non-compliance with treatment.
However, accurate communication between clinicians and patients of the cardiovascular, cerebrovascular, renal and neurodegenerative risks of hypertension will be only one part of the wider solution.
Improved monitoring and increasing awareness and detection of high blood pressure is being taken beyond GP clinics in Australia, including places like Bunnings Warehouse outlets in the latest Shop-to-Stop public health campaign. Novel developments in wearable devices may also be a game-changer on how the population can detect and monitor blood pressure in the future.
More intensive treatment is being recommended following trials including the SPRINT-MIND trial that found better outcomes for conservative blood pressure targets of less than 120/80 mmHg, even in older persons.
Lifestyle interventions including exercise prescriptions and potassium-enriched salt substitutes are increasingly recognised and included in guidelines as effective interventions to reduce blood pressure.
Ultimately, through these public health strategies, we hope to see that rates of blood pressure control in Australia improve from 32% to at least 70%. Fundamentally, the challenge that faces us is translating numbers on the digital readout of the sphygmomanometer into the real and devastating risk to individuals’ kidneys, hearts, brains and — with the new evidence on dementia — their minds and very identities.
Dr Matthew Lennon MD, PhD is a conjoint lecturer at the University of New South Wales.
Professor Aletta E Schutte PhD is a professor of cardiovascular medicine at the George Institute for Global Health and School of Population Health at University of New South Wales.
Ruth Peters PhD is an associate professor at the George Institute for Global Health Australia, School of Public Health at the Imperial College, London and at Neuroscience Research Australia, University of New South Wales.
Professor Perminder S. Sachdev MD, PhD is a scientia professor of neuropsychiatry at the University of New South Wales.
Dr Matthew Lennon acknowledges the Avant Foundation for providing funding for the Early Career Medical Researcher part-time scholarship.
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
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