Led by Rachel A. Whitmer, PhD, of Kaiser Permanente Division of Research in Oakland, California, the research looked at 7,238 men and women who were part of the Kaiser Permanente Northern California health care system.
The participants all had blood pressure checks and other tests from 1964 to 1973 when they were an average age of 33, and then again when they were an average age of 44.
Around 22 percent of the participants had high blood pressure in their 30s (31 percent of men and 14 percent of women) and around 22 percent also had high blood pressure in their 40s, however by this time the figure for men had decreased to 25 percent, while the number of women had increased to 18 percent.
Next, the team followed participants for 15 years to see who went on to develop dementia.
The results showed that high blood pressure in early adulthood or during the 30s was not associated with increased risk of dementia.
However, women who developed high blood pressure in their 40s were 73 percent more likely to develop dementia than women who had stable, normal blood pressure throughout their 30s and 40s.
The team also found that for women who made it to age 60 without developing dementia, the cumulative 25-year risk of developing the condition was 21 percent for those who had high blood pressure in their 30s, compared to 18 percent for those who had normal blood pressure in their 30s.
The results still held true even after the researchers had taken into account other factors that could affect risk of dementia, such as smoking, diabetes and body mass index.
“High blood pressure in midlife is a known risk factor for dementia, but these results may help us better understand when this association starts, how changes in blood pressure affect the risk of dementia and what the differences are between men and women,” said Whitmer, commenting on the findings.
“Even though high blood pressure was more common in men, there was no evidence that having high blood pressure in one’s 30s or 40s increased the risk of dementia for men,” Whitmer said. “More research is needed to identify the possible sex-specific pathways through which the elevated blood pressure accelerates brain aging.”