Untreated high blood pressure may raise Alzheimer’s disease risk

• Previous research shows several health concerns can increase a person’s risk of developing Alzheimer’s disease, including high blood pressure.
• Researchers estimate 46% of adults worldwide do not know they have hypertension.
• Researchers from the University of New South Wales have found people with untreated high blood pressure may have an increased risk of developing Alzheimer’s disease compared to people who have been or are being treated for hypertension.

Previous research shows there are a number of health concerns that can increase a person’s risk of developing a type of dementia called Alzheimer’s disease , including type 2 diabetes , obesity , high cholesterol , and stroke .

High blood pressure is also a known risk factor for Alzheimer’s disease — a condition for which there is currently no cure.

A new study has found that people with untreated high blood pressure may have an increased risk of developing Alzheimer’s disease compared to people who have been or are being treated for hypertension.

“There are many preventable risk factors for dementia but hypertension remains the most prevalent — affecting 1.3 billion people worldwide,” Matthew J. Lennon, MD, PhD , lead author of the study, and post-doctoral researcher at the Centre for Healthy Brain Ageing at the University of New South Wales and psychiatric Registrar at Royal North Shore Hospital in Australia, told Medical News Today .

“Given how much progress we have to make with regards to hypertension we thought that understanding its exact relationship to dementia was a crucially important public health question,” he said.

The study is published in Neurology , the medical journal of the American Academy of Neurology.

Untreated hypertension linked to 42% higher Alzheimer’s risk

For this study, Lennon and his team analyzed data from more than 31,000 people with an average age of 72 who were enrolled in 14 studies measuring cognitive change and dementia diagnosis from 14 countries, including Australia, the U.S., Spain, and Japan.

When reviewing blood pressure data for all participants, researchers found that 9% had untreated high blood pressure, 51% were currently taking hypertension medications, 36% did not have high blood pressure, and 4% were noted as uncertain.

“Hypertension may [be] the most underdiagnosed and poorly controlled [risk factor for dementia]. An estimated 46% of adults worldwide with hypertension do not know that they have it and of those with hypertension only around one in five (21%) have it adequately controlled,” Lennon said.

After adjusting for factors such as gender, age, and education level, Lennon and his team found the study participants with untreated high blood pressure had a 36% increased risk of developing Alzheimer’s disease when compared to people without high blood pressure.

When compared to people with hypertension who were taking blood pressure medications, the researchers found that those with untreated high blood pressure had a 42% heightened Alzheimer’s disease risk.

Lennon said they were surprised by the study’s findings.

“When we had covered the literature thoroughly there were few other studies that had found such a large difference in Alzheimer’s dementia risk between those with treated versus untreated hypertension,” he explained. “It really emphasized the importance of blood pressure management even in late life.”

“While our results seem to indicate that those with treated hypertension seem to have a lower risk of Alzheimer’s dementia than those with no history of hypertension at all, this should be interpreted carefully as the risk difference between these two groups was not statistically significant.”
— Matthew J. Lennon, MD, PhD

Greater hypertension vigilance needed

Lennon and his team hope their findings will stress to doctors the importance of discussing high blood pressure treatment to their patients.

“Particularly as people age, their own and their doctors’ views of managing their chronic illnesses such as hypertension can become less vigilant,” Lennon said. “This is particularly true of hypertension because in the moment it is almost universally asymptomatic — a silent killer. Doctors need to give their patients accurate, reliable information about the risks of not taking effective antihypertensive medications , as well as the risks and side effects of taking medication.”

“Our findings will help give older persons more data, more information on whether taking antihypertensives will be the right decision for them, with a greater weight on the protective cognitive effects of antihypertensives.”
— Matthew J. Lennon, MD, PhD

“While we have looked at cognition and dementia as a singular, binary concept in this paper (i.e. you have dementia or you do not have dementia) in our ongoing research we are breaking down cognition into subdomains and examining whether blood pressure and antihypertensives affects different cognitive functions in different ways. We have had some exciting and interesting preliminary findings which should hopefully be coming out in the near future!” he added.

Treating hypertension may help lower dementia risk

MNT also spoke with Cheng-Han Chen, MD , a board certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, about this study.

“Hypertension is a known significant risk factor for cardiovascular and cerebrovascular disease,” Chen said.

“While it was also known as a risk factor for developing vascular dementia , this meta-analysis also revealed an association between untreated hypertension and Alzheimer’s dementia. This finding further highlights the importance of treating hypertension and demonstrates the impact of elevated blood pressure on the many different organ systems in our body.”
— Cheng-Han Chen, MD

Chen said it is not entirely clear how untreated high blood pressure is associated with increased risk of Alzheimer’s dementia.

“It is possible that there is overlap between the diagnoses of Alzheimer’s and vascular dementia,” he continued. “It is also possible that the direction of the relationship is in reverse, i.e. that patients with Alzheimer’s are less likely to make regular doctor’s visits, and thus have elevated blood pressures at home that remain untreated.”

“These findings further demonstrate the significance of hypertension as a modifiable risk factor in so many different disease states,” Chen added. “Future research should investigate the longer-term relationship between hypertension and Alzheimer’s, extending back into middle age.”