High blood pressure in middle age may play affect memory and thinking in old age, according to a recent study.

Researchers found that in people with a history of high blood pressure in middle age, lower diastolic blood pressure in older age was associated with smaller total brain and gray matter volumes.

"Our findings bring new insight into the relationship between a history of high blood pressure, blood pressure in old age, the effects of blood pressure on brain structure, and memory and thinking," Lenore J. Launer, study author and a member of the American Academy of Neurology, said in a statement.

For the study, scientists measured the blood pressure of more than 4,000 middle-aged adults free of dementia. When they were in late life (average age of 76 years old), researchers remeasured their blood pressure and participants underwent MRIs that looked at structure and damage to the small vessels in the brain. They also took tests that measured their memory and thinking ability.

Researchers found that the association of blood pressure in old age to brain measures depended on a history of blood pressure in middle age.

Based on their findings, people with a history of high blood pressure in middle age, lower diastolic blood pressure in older age was associated with smaller total brain and gray matter volumes. This finding was reflected in memory and thinking performance measures as well. In people with high blood pressure in middle age, lower diastolic blood pressure was associated with 10 percent lower memory scores.

"Older people with a history of high blood pressure but who currently have lower blood pressure might have more extensive organ damage and are at risk of brain shrinkage and memory and thinking problems," Launer said.

They also found that older people without a history of high blood pressure but who currently have high blood pressure "are at an increased risk for brain lesions, suggesting that lowering of blood pressure in these participants might be beneficial."

The findings were recently published in the online issue of Neurology, the medical journal of the American Academy of Neurology.