Women who developed high blood pressure in mid-adulthood (40s) were 73 percent more likely to develop dementia than women who had stable, normal blood pressure throughout early- and mid-adulthood (30s and 40s), according to a Kaiser Permanente study published online today in Neurology. There was no evidence of this increased risk in the men studied.
"Despite the fact that the men in our study were more likely to have high blood pressure at all ages, developing high blood pressure in mid-adulthood was a risk factor for dementia only in the women," said senior author Rachel A. Whitmer, PhD, research scientists with the Kaiser Permanente Division of Research in Oakland, Calif.
Hypertension in midlife is a known risk factor for dementia, the study authors noted, but possible sex differences in the link between hypertension throughout early and mid-adulthood and dementia have not been evaluated.
The researchers studied 5,646 health plan members who had participated in Kaiser Permanente's world-renowned multiphasic examination, an optional checkup provided to members in San Francisco and Oakland, Calif., from the 1960s to 1980s. The checkup participants all had blood pressure and other tests from 1964 to 1973, when they were an average age of 33; and 1978 to 1985, when when they were an average age of 44.
Between 1996 and October 2015, 532 people (9.4 percent) in the cohort developed dementia; 298 were men, and 234 were women.
Hypertension and pre-hypertension in early-adulthood were not associated with elevated dementia risk in both men and women. But for women who developed hypertension in mid-adulthood, the risk of dementia was significantly higher (73 percent) than women who had stable, normal blood pressure throughout early- and mid-adulthood.
The results were the same when researchers adjusted for other factors that could affect risk of dementia, such as smoking, diabetes and body mass index.
"Our results show the importance of delineating the timing of risk factors in both sexes," said lead author Paola Gilsanz, ScD, research fellow with the Kaiser Permanente Division of Research. "In future studies, we'll be looking at how risk factors may have different impacts at different times in life for women compared to men."
This study is part of Whitmer's ongoing body of research at Kaiser Permanente to better understand dementia and cognitive aging. Whitmer has used the multiphasic data, paired with comprehensive data from Kaiser Permanente's electronic health record, to identify risk factors such as smoking, hypertension, depression, cholesterol, diabetes, obesity and others in more than 20 studies. With over $30 million in funding from the National Institute on Aging, Whitmer has launched the KHANDLE (Kaiser Healthy Aging and Diverse Life Experience) study, the Kaiser STAR (Study of Healthy Aging in African-Americans), and Life After 90 studies. These studies are matching multiphasic data with cognitive information and brain imaging scans to evaluate how risk factors over the life course affect brain health.
The study was supported by the National Institute on Aging.
In addition to Whitmer and Gilsanz, co-authors were Charles Quesenberry, PhD, of the Kaiser Permanente Division of Research; Elizabeth Rose Mayeda, PhD, and M. Maria Glymour, ScD, of the University of California, San Francisco; and Dan M. Mungas, PhD, and Charles DeCarli, MD, of the University of California, Davis.