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High Blood Pressure Linked to Dementia in Women

Older women with high blood pressure are at an increased risk of developing dementia, which might be slowed through aggressive anti-hypertensive therapy, researchers report.

According to a report in the Journal of Clinical Hypertension, high blood pressure – or hypertension – can actually cause the brain lesions that trigger dementia. Researchers drew their conclusions from data in the Women’s Health Initiative Memory Study (WHIMS) of women age 65 and older.

 

The research was conducted as part of the Women’s Health Initiative (WHI), the largest multi-site longitudinal study looking at health risks among postmenopausal women. WHIMS, which involves a subgroup of the women enrolled in WHI, looks at the influence of hormone therapy on thinking and memory.

 

Upon enrolling in the trial and annually during their participation in it, the women had their blood pressure measured and underwent tests to measure their cognitive ability. Some of the WHIMS participants -- 1,403 of them -- also underwent magnetic resonance imaging (MRI) in 2005 and 2006. All of these women were free of dementia when they enrolled, said the researchers who represented various academic facilities.

 

The MRI studies revealed that women who, on entry to the WHIMS trial, had elevated blood pressure (defined as systolic blood pressure reseedings over 140, or diastolic blood pressure over 90, or being on antihypertensive drug therapy), also had significantly higher amounts of white matter lesions (so-called WMLs) when they underwent MRIs eight years later. Normal blood pressure is defined as a systolic blood pressure of 120 or less and a diastolic pressure of 80 or less.

 

“Based on our findings, we would encourage women to maintain their blood pressure at normal levels, which may reduce their risk of dementia,” says study co-author Dr. Sylvia Wassertheil-Smoller, professor of epidemiology and population health at Albert Einstein College of Medicine at Yeshiva University in New York.

 

The small blood vessels in the brain are especially susceptible to damage from even moderately elevated blood pressure-- resulting in damage to the white matter served by those vessels. The brain’s white matter is composed of whitish myelin-coated axons (nerve cell appendages) that allow nerve cells to communicate with each other and help the regions of the brain work together. Several studies have found that damage to white matter, as indicated by the presence of WMLs, seems to be an independent risk factor for dementia.

 

The current study reinforces earlier research showing that hypertension plays a role in causing dementia, suggesting that preventing hypertension from developing -- through weight loss, exercise or other lifestyle changes-- would be beneficial, the research team reported.

 

“However, we don’t know whether hypertension treatment will prevent WMLs from developing, or how much blood pressure should be lowered so that these brain lesions won’t occur,” says Wassertheil-Smoller. “We do have suggestive evidence that the progression of WMLs can be slowed by anti-hypertensive therapy.”

 

“Nonetheless,” she adds, “it would be prudent for women to keep their blood pressure low, and the earlier in life they start doing so, the better. At present, keeping blood pressure at normal levels is probably the most effective way we know of to prevent dementia from occurring.”

 

Wassertheil-Smoller notes that high blood pressure is also a major risk factor for stroke, “so it is certainly not good for the brain.” She says that further clinical trials are needed to better establish whether anti-hypertensive therapy can prevent or slow WMLs, and, if so, to find the specific drug therapies that work best.

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