Cheap pills that help to lower blood pressure could also prevent Alzheimer's disease, according to new research.
A study of almost 11,000 people found those taking the drugs for high blood pressure had slower rates of mental decline, 7NEWS.com.au reports.
Their brain power was found to be as good as peers free of high blood pressure, which is known to increase the risk of dementia.
Lead author Doctor Shumin Rui, a public health statistician at Columbia University in New York, said: "We think efforts should be made to expand high blood pressure screenings, especially for at-risk populations.
"So many people are not aware that they have high blood pressure that should be treated."
Rui said the finding presented at an American Heart Association (AHA) meeting in New Orleans is important.
It was based on an analysis of data from a retirement survey of over 55s in China between 2011 and 2015. Overall, cognition problems increased over the four years.
But those who had high blood pressure, or hypertension, that was not being treated showed a more rapid rate of decline.
This was compared to participants receiving therapy for it - and those who did not have the disorder. In fact, the mental faculties of these two groups were similar.
"High blood pressure, or hypertension, and cognitive decline are two of the most common conditions linked to ageing. More people are living longer worldwide," Rui said.
"We need to better understand how high blood pressure treatments may protect against cognitive decline and look at how high blood pressure and cognitive decline are occurring together."