When some people stand up from sitting or lying down, they may feel dizzy or even faint because of a sudden drop in blood pressure. That phenomenon, which becomes more common in older adults, is called orthostatic hypotension.
Previous research has suggested a link between orthostatic hypotension, or OH, and dementia, though scientists don't understand why. But a new study published Monday in the American Heart Association journal Hypertension refines that connection, concluding that the blood pressure drop in the first minute after standing up is most strongly associated with developing dementia.
"What is new in this study is the early drop in blood pressure and the relevance of this to risk of dementia," said Dr. Yuan Ma, an assistant professor of epidemiology at Harvard's T.H. Chan School of Public Health in Boston and lead author of the study.
The researchers drew on data collected since the late 1980s in the landmark and ongoing Atherosclerosis Risk in Communities Study, known as ARIC. During the first visit, participants had their blood pressure checked while lying down, then five times in the first two minutes after standing up.
Among 11,644 participants, who were 55 years old on average at the start of the study, about 1 in 5 had developed dementia a median of 26 years later.
Compared to those who didn't experience dizziness, participants who felt dizzy upon standing had much larger drops in systolic blood pressure (the top number in a blood pressure measurement) during the first minute after standing up. Those whose systolic blood pressure declined by 20 mmHg or more in the first 30 seconds after standing had a 22% higher risk of dementia compared to those whose blood pressure remained stable. Drops in blood pressure after the first minute had much less impact.
"These early drops in blood pressure usually are not checked when patients go to their doctors," Ma said. "This study suggests that doctors need to pay more attention to these early abrupt drops in blood pressure because they could be a sign that someone is at a higher risk of developing dementia." Even so, she cautioned that because of the study's design, "we cannot draw any causal conclusion. We don't know if the early drop in blood pressure leads to dementia, or the other way around."
In subsequent research, she said, scientists hope to figure out what is happening in the brain that leads to this rapid drop in blood pressure upon standing.
"A healthy individual has a system that can maintain blood pressure relatively stable," Ma said. "The blood pressure will still drop when we change our position from lying down to standing up, but it shouldn't be a large, rapid drop. We don't know exactly why a large, rapid drop happens, but it's something we're working to understand. It increases with age, and that's a bad thing."
Dr. Costantino Iadecola, a neurologist and director of the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine in New York City, said the study underscores the need for health care professionals to check for orthostatic hypotension in their patients.
"This is a refinement of what has been established previously," said Iadecola, who was not involved in the new study. "If the patient says, 'Look, I feel a little dizzy,' the doctor should check the changes in blood pressure produced by standing. If there is a severe drop within one minute of standing, that should be an alarm bell that we've got to take care of this and maybe do some treatment that will minimize the change."
For older people already with cognitive deficiency or balance issues, both doctors said orthostatic hypotension adds to the risk of falls, broken bones and death. "People should be mindful of their surroundings and their environment," Ma said.
To help prevent falls, the National Institute on Aging suggests strategies such as doing strength and balance exercises, installing night lights around the house and grab bars in the bathroom, and using a cane or walker if necessary. For people with orthostatic hypotension, a 2022 scientific statement from the AHA offers suggestions such as wearing compression stockings, pumping the legs when standing, and working with their doctor to adjust any medications they take that are causing or worsening the condition.
Ma said changes in the brain that can develop into Alzheimer's disease or other types of dementia can take place years before any symptoms appear. That makes it even more important, she said, to minimize cardiovascular risk factors throughout life.
Those include not smoking, staying physically active, maintaining a healthy weight and a healthy diet, getting enough sleep, and keeping blood sugar, cholesterol and blood pressure under control.
"Controlling the factors of cardiovascular disease at least potentially reduces the risk of Alzheimer's disease and dementia as well," Ma said. "The benefits are likely to be larger if you start early in life.
"What's good for the heart," she said, "is good for the brain."