High blood pressure, or hypertension, appears to be associated with an increased risk for mild cognitive impairment according to Christiane Reitz, M.D., Ph.D., and colleagues at the Columbia University Medical Center, New York.

Researchers followed 918 Medicare recipients with an average age of 76.3-years. None of the participants showed signs of cognitive impairment at the beginning of the study. All participants underwent an initial interview and physical examination, along with test of cognitive function, and then were examined again approximately every 19 months for an average of 4.7 years.

During the follow-up period 36% of the participants developed mild cognitive impairment, which breaks down to 17% of cases involving amnestic mild cognitive impairment (that means low scores on the memory portions of the neuropsychological tests) and 19% of non-amnestic mild cognitive impairment. High blood pressure was associated with an increased risk of all types of mild cognitive impairment that was mostly driven by an increased risk of non-amnestic mild cognitive impairment; hypertension was not associated with amnestic mild cognitive impairment, nor with the change over time in memory and language abilities.

The mechanisms by which blood pressure affects the risk of cognitive impairment or dementia remain unclear. Possible reasons suggested by the researchers include:

• Hypertension may cause cognitive impairment through cerebrovascular disease.
• Hypertension is a risk factor for subcortical white matter lesions found commonly in Alzheimer’s disease.
• Hypertension may also contribute to a blood-brain barrier dysfunction, which has been suggested to be involved in the cause of Alzheimer’s disease.
• Other possible explanations for the association are shared risk factors, including the formation of cell-damaging compounds known as free radicals.

Researchers believe their findings support the hypothesis that hypertension increases the risk of incident mild cognitive impairment, especially non-amnestic mild cognitive impairment and that preventing and treating hypertension may have an important impact in lowering the risk of cognitive impairment.