Onset of high blood pressure later in life, especially at age 80 or beyond, is associated with lower dementia risk after 90, according to a new study, PTI reported.
High blood pressure and other heart health risk factors were generally thought to up risk of dementia.
Researchers at the University of California, Irvine in the US followed 559 people to study the relationship between dementia, age of hypertension onset and blood pressure measurements. The study was conducted over 2.8 years.
All participants were from ongoing, long-term study of people aged 90 and older known as 'The 90+ Study'. Participants did not have dementia at enrolment and were 93 years old on average and 69 per cent female.
The participants were assessed every six months for dementia during the study period and during the follow up period, 224 (40 per cent) of the participants were diagnosed with dementia.
The researchers found that participants who reported hypertension onset at age 80 to 89 were 42 per cent less likely to develop dementia after age 90 as against those who reported no history of high blood pressure.
In middle age, high blood pressure - also called hypertension increased dementia risk later in life, said study lead researcher Maria Corrada. It also raises one's risk for heart attack and stroke.
However, the onset of hypertension in the eighth or ninth decade of life was linked to lower risk of mental decline in one's 90s, the team found.
"Hypertension in the very old is not detrimental for mental health," said Corrada, a professor of neurology and epidemiology at the University of California, Irvine, PTI reported.
According to Corrada several factors might help explain the apparent association between late-life high blood pressure and lower dementia risk.
For one, as people aged, blood pressure might increase to keep blood flowing to the brain for normal functioning.
"It's a matter of creating enough pressure to get blood to oxygenate the brain adequately," Corrada said.