Getting high blood pressure under control could potentially help prevent memory troubles, U.S. researchers say.

People aged 45 and older with high diastolic blood pressure — high readings on the bottom number of the blood pressure reading — were more likely to have problems with their memory and thinking skills than those with normal readings, the team reported in Tuesday's issue of the journal Neurology. 

'It's possible that by preventing or treating high blood pressure, we could potentially prevent cognitive impairment, which can be a precursor to dementia.'— Dr. Georgios Tsivgoulis

Every 10-point increase in the reading was associated with  seven per cent higher odds of cognitive impairment, which can be a precursor to dementia, the researchers said.

"Higher diastolic blood pressure was cross-sectionally and independently associated with impaired cognitive status in this large, geographically dispersed, race- and sex-balanced sample of stroke-free individuals," the researchers concluded in the study.

The finding held after researchers accounted for other factors that could affect thinking skills, such as age, education level, smoking and other illnesses such as diabetes.

"It's possible that by preventing or treating high blood pressure, we could potentially prevent cognitive impairment, which can be a precursor to dementia," Dr. Georgios Tsivgoulis of the University of Alabama at Birmingham, who led the study, said in a statement.

Damage to brain's blood vessels

It's not known why diastolic pressure, which is taken while the heart is relaxing, seems to be linked to mental ability.

The researchers hypothesized it could be because diastolic pressure speeds up damage from hardening of arteries in the brain and changes in the force applied when blood spreads through vessels in the brain.

Further study will be needed to understand whether higher blood pressure may be a risk factor for cognitive decline, said Dr. Walter Koroshetz, deputy director of the National Institute of Neurological Disorders and Stroke, which funded the study.

Previous studies probing the link looked at different ages, and races and defined cognitive impairment and blood pressure cutoffs in different ways, which may explain why the association hasn't been observed before, the researchers said.

This study looked at nearly 20,000 people age 45 and older across the U.S. who had never had a stroke or mini-stroke.  It aimed to determine why blacks are more likely to die of strokes than other Americans.

The National Institutes of Health is organizing a large clinical trial to test whether aggressive blood pressure lowering offers health benefits, including staving off cognitive decline, Koroshetz said.

Some of the study's authors reported receiving research support or working as consultants for several pharmaceutical companies.