Hypertension linked to dementia in older women

Study adds to evidence that high blood pressure causes brain lesions

BRONX, 13 jan 2010— Older women with hypertension are at increased risk for developing brain lesions that cause dementia later in life, according to data from the Women's Health Initiative Memory Study (WHIMS). The findings were published in the December 2009 online issue of the Journal of Clinical Hypertension.

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. All the women in WHIMS were 65 or older.

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) at 14 U.S. academic centers in 2005 and 2006. All of these women were free of dementia when they enrolled. Examination of the data on these 1,403 women was led by Lewis H. Kuller, M.D., Dr.P.H., of the University of Pittsburgh, in conjunction with researchers at other WHI centers, including Dr. Sylvia Wassertheil-Smoller, Ph.D., professor of epidemiology and population health and the Dorothy and William Manealoff Foundation & Molly Rosen Chair in Social Medicine at Albert Einstein College of Medicine. Dr. Wassertheil-Smoller is also the principal investigator of Einstein's WHI and WHIMS studies.

The MRI studies revealed that women who, on entry to the WHIMS trial, had elevated blood pressure (defined as systolic blood pressure ≥140 mmHg, or diastolic blood pressure ≥ 90 mmHg, or being on antihypertensive drug therapy), had significantly higher amounts of white matter lesions (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. Wassertheil-Smoller.

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.

"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 Dr. 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." According to baseline data on more than 98,705 women ages 50-79 who enrolled in the WHI study, 37.8% had hypertension, which is defined as systolic blood pressure ≥140 mm Hg and/or diastolic blood pressure ≥90 mm Hg or being on medication for high blood pressure; 64.3% of the hypertensive women were treated with drugs, and blood pressure was controlled in only 36.1% of the hypertensive women, with lower rates of control in the oldest group.

Dr. 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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The study, "Relationship of Hypertension, Blood Pressure (BP) and BP Control with White Matter Abnormalities in the Women's Health Initiative Memory Study (WHIMS) MRI Study," was published in the December 16 online edition of the Journal of Clinical Hypertension. Other contributors include: Karen L. Margolis, M.D., Health Partners Research Foundation, Minneapolis, Minn.; Sarah A. Jaramillo, M.S. and Jeff Williamson, M.D., Wake Forest University School of Medicine, Winston-Salem, N.C.; Nick R. Bryan, M.D., University of Pennsylvania, Philadelphia, Penn.; Diana Kerwin, M.D., Froedtert & Medical College of Wisconsin, Milwaukee, Wis.; Marian Limacher, M.D., University of Florida, Gainesville, Fla.; and Jennifer G. Robinson, M.D., M.P.H., University of Iowa, Iowa City, Iowa.