Sudden drops in blood pressure may increase risk of dementia

Dementia affects tens of millions of people in the United States. New research suggests that those who experience sudden blood pressure drops in their middle age may be more likely to develop dementia in old age.

Alzheimer's disease, the most common form of dementia, currently ranks as the sixth leading cause of death in the U.S. In fact, it is estimated that 1 in 3 U.S. elders dies with a form of dementia.

New research indicates that middle-aged people who experience sudden drops in their blood pressure (BP) may be at risk of developing dementia and serious cognitive decline when they reach old age.

The study was conducted by researchers from the Johns Hopkins Bloomberg School of Public Health in Baltimore, MD, and the findings were presented at the American Heart Association's Epidemiology and Prevention/Lifestyle 2017 Scientific Sessions in Portland, OR.

Chronically low BP may cause dizziness, fatigue, nausea, or fainting. Temporary, rapid drops in BP bear the name "orthostatic hypotension" (OP) and may cause serious damage; they stop the necessary blood flow from reaching the brain.

Previous studies have indicated a link between OP and cognitive impairment in seniors, but the new Johns Hopkins study - led by Andreea Rawlings, Ph.D., a post-doctoral researcher in the Department of Epidemiology at the Bloomberg School - is the first to examine the long-term correlations between the two.

The researchers examined clinical data from the Atherosclerosis Risk in Communities study, which collected information on 15,792 participants aged between 45 and 64 in 1987, the year of enrollment.

Patients with OP are 40 percent more likely to have dementia

For the new study, Rawlings and team isolated the data on 11,503 patients who had no history of heart disease and visited the hospital for the first time. Scientists took the patients' BP after they had lay down for 20 minutes.

The researchers defined OP as a rapid drop of 20 millimeters of mercury (mm Hg) or more in systolic BP, or 10 mm Hg or above in diastolic BP.

Approximately 6 percent of the participants, or 703 individuals, met these criteria.

The team clinically followed the participants for the following two decades or more.

They found that people with OP upon their first visit had a 40 higher risk of developing dementia than their OP-free counterparts. Patients with OP also had 15 percent more cognitive decline.

"Even though these episodes are fleeting, they may have impacts that are long lasting. We found that those people who suffered from orthostatic hypotension in middle age were 40 percent more likely to develop dementia than those who did not. It is a significant finding and we need to better understand just what is happening."

Andreea Rawlings, lead author

As this is an observational study, researchers cannot establish causality or explain whether OP is an indicator of another disease responsible for the cognitive decline. However, they speculate that the decrease in the blood flow to the brain may play a role.

The lead author of the study also acknowledges the study's limitation that arises from not knowing whether the patients had a singular episode of OP, or whether they had lived with the recurring symptoms over time.

"Identifying risk factors for cognitive decline and dementia is important for understanding disease progression, and being able to identify those most at risk gives us possible strategies for prevention and intervention," Rawlings says. "This is one of those factors worth more investigation."

Learn how high BP is linked to a lower risk of Alzheimer's.