Women and Dementia: What Role Does Blood Pressure Play?

Elevated systolic blood pressure (SBP) in older women predicted their risk of mild cognitive impairment and cognitive loss, data from the Women's Health Initiative Memory Study (WHIMS) cohort showed.

Higher SBP was tied to a rising risk of mild cognitive impairment and cognitive loss (tests for trends across blood pressure categories P<0.01) , reported Longjian Liu, MD, of Drexel University in Philadelphia, and co-authors in Lancet Healthy Longevity. The relationship was not significant for probable dementia.

Older women with hypertension with controlled SBP lower than 120 mm Hg, however, were not at increased risk of mild cognitive impairment (HR 1.33, 95% CI 0.98-1.82, P=0.071) or cognitive loss (HR 1.09, 95% CI 0.82-1.44, P=0.57) compared with women who had normal blood pressure.

Women on anti-hypertensive treatment whose pulse pressure (PP; systolic minus diastolic blood pressure) was less than 50 mm Hg also did not have a significantly higher risk of mild cognitive impairment (HR 1.26, 95% CI 0.98-1.62, P=0.07) or cognitive loss (HR 1.17, 95% CI 0.94-1.46, P=0.16).

"These results add new evidence that decreased SBP and PP levels might have a pivotal role in preserving cognitive health in older women," Liu and colleagues wrote.

Epidemiological studies have shown that higher midlife blood pressure predicts later cognitive impairment, noted Philip Gorelick, MD, MPH, and Farzaneh Sorond, MD, PhD, both of Northwestern University in Chicago, in an accompanying editorial.

"However, the association of elevated BP as a predictor of dementia is less clear in older people," Gorelick and Sorond pointed out.

"A major guideline on BP control from the American College of Cardiology, American Heart Association, and other expert groups concludes that it is reasonable to lower BP in people with hypertension to prevent cognitive decline and dementia, but the guidance does not set a firm target for BP lowering," they wrote.

The SPRINT MIND substudy of the SPRINT trial "allayed some clinical concerns" by showing that targeting SBP to less than 120 mm Hg was relatively safe and showed benefits on mild cognitive impairment, though it did not meet its primary outcome of reducing probable dementia, Gorelick and Sorond observed. The ongoing SPRINT MIND 2.0 trial, a 2-year continuation of SPRINT MIND, may clarify the role of blood pressure in dementia risk.

"There remain subgroups of study participants, such as older women, who have not been well represented in randomized controlled trials or observational studies of BP and cognition," they noted.

Liu and co-authors evaluated 7,207 women ages 65 to 79 in the WHIMS cohort recruited from May 1996 through December 1999 at 39 U.S. clinical centers and followed until December 2019. Blood pressure was measured at baseline and cognitive function was assessed annually. Hypertension was defined using the American Heart Association 2017 guideline for high blood pressure.

Median follow-up was 9 years. Outcomes were mild cognitive impairment, probable dementia, and cognitive loss (a combined endpoint of either mild cognitive impairment or probable dementia, or both).

Over the follow-up period, 15.7% of participants were classified as having mild cognitive impairment, 10.3% were classified as having probable dementia, and 21.3% met criteria for cognitive loss.

Incidence rates per 1,000 person-years were 15.3 cases for mild cognitive impairment, 9.7 cases for probable dementia, and 20.3 cases for cognitive loss. There were no significant associations between hypertension, SBP, or PP with probable dementia.

"Evidence on whether controlled SBP at less than 120 mm Hg or PP at less than 50 mm Hg are associated with risk reduction of probable dementia remains uncertain," Liu and co-authors wrote. "This lack of evidence is probably due to a small sample size of those with diagnosed probable dementia."

"However, the significant associations of hypertension, elevated SBP, and PP with risk of mild cognitive impairment and cognitive loss support that intensive control of hypertension, SBP, and PP levels can preserve cognitive health in older women," they added.

The study had several limitations, the researchers acknowledged. Blood pressure was assessed late in life and no corresponding data on midlife blood pressure were collected. In addition, participants were mainly white; results may not apply to other racial and ethnic groups.

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