New research shows that there may be a link between high blood pressure at night and dementia for older men.

Researchers are increasingly learning how hypertension or high blood pressure is linked to the risk of developing certain forms of dementia, including Alzheimer’s disease.

This week a new study published in the medical journal Hypertension found that older men who have higher blood pressure readings at night may be at higher risk for certain types of dementia.

“The link between hypertension and Alzheimer’s disease has been known for years and our study makes a further step by focusing on the circadian pattern of blood pressure and the risk of Alzheimer’s disease,” study author Xiao Tan, PhD, postdoctoral researcher at Uppsala University, told Healthline.

Blood pressure can vary throughout the day but the lowest point is traditionally at night. This drop in blood pressure at night is called dipping. However, for some people, this pattern is reversed and the nighttime blood pressure is higher than it is in the daytime, a phenomenon called reverse dipping.

“High blood pressure at night has been linked to a higher risk of cardiovascular disease events, like heart attack, stroke, hospitalization for heart failure, and cognitive dysfunction,” said Dr. Joshua A. Beckman, director of vascular medicine and co-director of the Vanderbilt Vascular Biology Center at the Vanderbilt Medical Center.

What the study found

Researchers at Uppsala University in Sweden conducted a study evaluating the association of nighttime hypertension and Alzheimer’s in about 1,000 Swedish men.

They used data from the Uppsala Longitudinal Study of Adult Men and measured the 24-hour blood pressure of men who were in their early 70s, and then again 7 years later.

Follow-up with these patients continued for up to 24 years until participants were in their 90s.

The researchers found that the risk of developing forms of dementia including Alzheimer’s was 1.64 times higher among men with reverse dipping compared to those who didn’t experience this phenomenon.

However, rates of vascular dementia, in which people experience a decline in cognitive skills, didn’t increase in men with reverse dipping.

Beckman said the duration of the study and the findings will help experts better understand the connection between high blood pressure and dementia risk.

“This recent work in the journal Hypertension extends our understanding of high blood pressure overnight,” he told Healthline. “It had a very long follow-up period of 24 years and more than one-third of the people being studied developed dementia, so there was a lot of data to work with.”

Beckman said the fact that reverse dipping was associated with increased forms of dementia including Alzheimer’s disease but not vascular dementia is “fascinating.”

“That suggests that high blood pressure is not just working through problems with blood vessels but through other mechanisms that we have to learn about,” he said.

While the study looked at men, Tan said it’s very possible this link between reverse dipping and dementia is also seen in women. Other recent research has shown how high blood pressure in both men and women may increase the risk of developing forms of dementia including Alzheimer’s disease.

“We think it is important to further investigate the link between blood pressure dipping and Alzheimer’s disease and women,” Tan told Healthline.

Why is reverse dipping a risk?

Nighttime is a critical period for brain health, and it’s a time when the brain can relax or even reset at night. A 2019 study published in Science found that the brain will “clear out” toxins at night, which otherwise could build up and affect neurons.

Experts have known there’s a link between brain health and blood pressure, and it’s believed that high blood pressure may interfere with some of the nighttime tasks of the brain.

Tan said that if a person has high blood pressure readings at night, it may mean their sleep is disrupted.

“Those with higher blood pressure at night may suffer from poor sleep quality,” Tan said. “Sleep is essential for the normal functioning of the glymphatic system.”

A buildup of this metabolic waste is believed to be a key issue for the onset of forms of dementia, specifically Alzheimer’s disease.

“One of the tasks of the brain overnight is the complete removal of waste products not cleared during the day,” Beckman said. “High blood pressure overnight may prevent the removal of these waste products leading to a brain trash buildup.”

Experts are also investigating if men with reverse dipping of blood pressure are at increased risk for sleep apnea, where breathing spontaneously starts and stops.

Blood pressure and overall health

Hypertension, or high blood pressure, occurs when the force of blood pushing against the walls of your blood vessels is too high. As blood pressure becomes chronic, arteries throughout the body develop buildup called atherosclerosis, which can lead to a host of health issues.

While some of these health issues are well known such as heart attacks and strokes, high blood pressure can also lead to other conditions that may be less well known such as vision loss and sexual dysfunction.

If you’re worried about high blood pressure or whether you could be at risk for reverse dipping, talk with your doctor. You may be able to wear an ambulatory blood pressure monitor that will measure your blood pressure over 24 hours.

If you have high blood pressure, it’s important to remember that taking preventive measures such as eating a balanced diet and staying active or taking medication can help keep high blood pressure and related conditions in check.

A 2019 study found that lowering one’s blood pressure can reduce a person’s risk of dementia and other brain dysfunction.

Studies have also shown that people who have high blood pressure and take their medications have less cognitive decline in comparison to those who don’t treat their blood pressure with medication.

Medical reference: Healthline