New research suggests that hypertension status in middle age may influence how the condition later affects memory and thinking in older age, with earlier blood pressure affecting two courses of mental decline.

Among 4,000 Americans followed over a quarter-century, those with no history of hypertension in middle age who developed the condition later were 50 percent more likely to have brain lesions. However, those who had high blood pressure earlier but experienced lower levels of diastolic levels later in life were more likely to have lower brain volumes and less grey matter.

Either way, changes in blood pressure status through life said much about differing risk profiles for mental decline in advanced age, according to investigator Lenore J. Launer of the National Institute on Aging. "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," she said in a press statement.

Study participants were measured for blood pressure at middle age and then allowed to age; later undergoing blood pressure testing again, along with a modern brain scan using functional-magnetic resonance imaging technology. Tests measuring memory and thinking ability were also administered to assess mental ability.

"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,” Launer said. “On the other hand, 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.”

Among those who only developed hypertension in older age, the condition was associated with a 10 percent decline in memory and thinking ability. “In this large population-based cohort, late-life blood pressure differentially affects brain pathology and cognitive performance, depending on the history of midlife hypertension," Launer and her colleagues wrote in the study. “Our study suggests history of hypertension is critical to understand how late-life blood pressure affects brain structure and function."

The study was published Wednesday in the journal Neurology.

Source: Launer L, Muller M, Sigurdsson S. Joint effect of mid- and late-life blood pressure on the brain. Neurology. 2014.