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Study Links High Blood Pressure With Early Cognitive Impairment

Mary Caffrey

Despite taking medication, patients who had high blood pressure alongside blood vessel damage in the brain’s white matter showed early signs of cognitive impairment, according to a  study appearing today in the journal Hypertension. The journal is published by the American Heart Association (AHA).

The findings may offer new clues about detecting who is at risk for early-stage dementia. High blood pressure is a known risk factor for stroke, vascular dementia, and possibly Alzheimer disease, but this study explored the more subtle loss of cognitive functioning that may start long before dementia occurs.

Rates of dementia and Alzheimer disease are rising as more people live longer with high blood pressure and diabetes, which are linked to microvascular issues that lead to cognitive decline. Last year, the AHA announced that 103 million adults in the United States have high blood pressures. In November 2017, the AHA and American College of Cardiology jointly announced a lower threshold for defining high blood pressure; the guidelines created a Stage 1 at 130/80 mmHg and Stage 2 at 140/ mmHg, with different treatment recommendations for each level.

In this new study from Spain, researchers used magnetic resonance imaging (MRI) to track what was happening in the patients’ brains, and specifically in the periventricular white matter in the center of the brain. This is the system of blood vessels that serves as a circuitry connecting the distant portions of the brain to each other; if damage occurs, this can affect cognitive function.

In the study,  345 patients, average age 65, were screened with an MRI and given a cognitive screening test and cognitive diagnosis to determine if they were experiencing normal aging or had mild cognitive impairment. Patients were screened at baseline and at follow up, and they were followed for an average of 4 years. Patients’ average blood pressure at follow up was 144.5/76.5 mmHg.

Researchers evaluated incident lacunar infarcts, which are tiny strokes deep in the white matter of the brain, and cerebral microbleeds. Over the study period, 9.1% of the patients developed mild cognitive impairment, and researchers found a measurable link between changes in the periventricular white matter and impairment.

Researchers qualitatively classified changes in the periventricular and deep white matter hyperintensities (WMH) as none, minor, or marked. The researchers noted, “Considering the progression of cerebral small vessel disease, the prevalence of incident infarcts was 6.1% and that of incident cerebral microbleeds was 5.5%; progression of periventricular WMH was 22% and that of deep WMH was 48%.”

Those with marked progression showed a significant decrease in global cognition, compared with patients without progression (adjusted mean [SE], −0.519 [0.176] vs 0.057 [0.044], respectively; P = .004) and a higher risk of incident mild cognitive impairment (OR, 6.184; 95% CI, 1.506–25.370; P = .011).

Thus, the researchers found, “Our results indicate that hypertensive patients with progression of periventricular WMH have higher odds of cognitive impairment, even in the early stages of cognitive decline.”

In most cases, this kind of mild decline would go unnoticed. However, if left untreated, more severe forms of cognitive could emerge, and the authors say more work is needed to understand how these comparatively mild levels of decline trigger severe forms of dementia.

“The brain is an organ expose to a high volume of blood flow and it is very vulnerable to sustained high blood pressure levels, and this might be happening silently or with mild symptos, but that doesn’t mean there aren’t consequences,” lead author Joan Jimenez Balado, who is a PhD candidate in neuroscience at the Institute de Recerca Hospital Vall d’Hebron in Barcelona, Spain, said in a statement. “High blood pressure and its consequences are really covert disease that tend to progress if not well managed.”

Reference
Jimenez-Balado J, Riba-Llena I, Abril O, et al. Cognitive impact of cerebral small vessel disease changes in patients with hypertension. [published online January 4, 2019]. Hypertension. doi: 10.1161/HYPERTENSIONAHA.118.12090.
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