Feeling dizzy after you stand up may be a predictor of dementia in later life, a study has claimed.
The complaint is caused by orthostatic hypotension, a form of low blood pressure that happens when you stand up.
Researchers at the University of California found people who suffered the problem were up to 40 per cent more likely to develop disease.
But the risk was only higher for people who had drops in systolic blood pressure, not diastolic.
The experts followed more than 2,000 people over the age of 70 for 12 years to see how the condition affected the risk of dementia.
Researchers suggested the temporary lack of blood flow to the brain can cause cognitive function to decline over time.
Blood pressure is written as two numbers; The first number is the systolic pressure. This is the pressure in the arteries when the heart beats and fills them with blood.
The second number is the diastolic pressure, which is the pressure in the arteries when the heart rests between beats.
When a person stands up from sitting or lying down, the body must work to adjust to that change in position.
If the body fails to push blood upward and supply the brain with oxygen, blood pressure falls and a person may feel lightheaded or even pass out.
Orthostatic hypotension (OH) — also called postural hypotension — is the term used to describe this.
As people get older, their major arteries get stiffer, which can means blood circulation isn’t as optimum as it once was. It’s thought this may be why problems like OH tend to be more common in the elderly.
The problem is thought to affect around five per cent of people younger than 50. But up to 20 per cent of people ages 70.
Only around two per cent of those affected suffer serious symptoms, such as dizziness, blurry vision and nausea.
The study by the University of California enrolled people of an average age of 73 who did not already have dementia.
Their blood pressure was measured when they were sitting down and then again after they stood up three times over the course of five years.
According to the American Academy of Neurology, the formal diagnosis of OH requires a 20mm Hg drop in systolic blood pressure or a 10mm Hg drop in diastolic blood pressure within three minutes of standing.
In this study, OH was defined as a fall of more than 15mm in systolic or more than 7mm in diastolic blood pressure because the participants were older.
A total of 15 per cent had orthostatic hypotension – when both types of blood pressure fell – on at least one of the visits.
Nine per cent had systolic orthostatic hypotension and 6.2 per cent had diastolic orthostatic hypotension on at least one of the visits.
Over 12 years, the participants were evaluated to see if anyone developed dementia.
A total of 462 people, or 22 per cent, developed the memory-robbing disease that affects an estimated 850,000 people in the UK and 5.7million in the US.
The people with systolic OH were 37 per cent more likely to develop dementia than those who did not have the condition, after adjusting for other factors that could affect their risk, such as diabetes, smoking and alcohol use.
Diastolic OH was not significantly linked with increased risk of dementia, however.
People with systolic OH were also divided into three groups based on how much their readings changed over time.
The findings, published in the journal of the American Academy, Neurology, show those whose readings changed the most were more likely to get dementia.
A total of 24 per cent of people in the group with the most fluctuation in systolic readings later developed dementia, compared to 19 per cent of the people in the group with the least fluctuation.
It means those in the highest group were 35 per cent more likely to develop dementia than those in the lowest group, after adjusting for other dementia risk factors.
The study author Dr Laure Rouch said: ‘People’s blood pressure when they move from sitting to standing should be monitored.
‘It’s possible that controlling these blood pressure drops could be a promising way to help preserve people’s thinking and memory skills as they age.’
The causes of dementia are not well understood, but it is known that factors like blood pressure, blood flow to the brain and cardiovascular health are linked to the risk of dementia – particularly vascular dementia.
In people with vascular dementia, brain scans often show up small areas of stroke where the brain has been starved of oxygen.
The latest study adds more weight to the theory that in order to maintain a healthy brain, it needs constant blood flow to supply cells with crucial oxygen.
But it did not make any distinctions between the type of dementia participants were diagnosed with, either Alzheimer’s disease or vascular dementia.
And the research was only observational, which means it cannot prove that feeling dizzy is linked with getting dementia.
Only a link between the two conditions was found – but it is not the first time it has been made.
Researchers in Holland also found link between blood pressure drops on standing and the chances of getting dementia. However, only 13 per cent with the condition said they suffered dizziness.
Orthostatic hypotension has also been recognised as a red flag for heart disease.
Researchers led by Harvard found that people with OH had a higher risk of future heart attack, heart failure, and stroke than those without the condition after tracking more than 9,000 middle-aged adults for two decades.