Hypertension's Role in Cognitive Decline

Patients who have hypertension may be at increased risk for cognitive decline and dementia. According to a study published in the October 2014 issue of JAMA Neurology, researchers have been trying to elucidate the timing and mechanism by which elevated blood pressure robs patients’ thinking abilities. Since hypertension is treatable, better information about its role in cognition could help public health advisors and clinicians promote early treatment.

Studies suggested that midlife (45-55 years of age) hypertension may be a stronger risk factor for cognitive decline than late-life hypertension. Researchers involved in the Atherosclerosis Risk in Communities cohort (1990-1992 through 2011-2013) used their data to evaluate the association between midlife hypertension and 20-year change in cognitive performance.

This study enrolled 13,476 participants who underwent baseline cognitive assessment. At 20 years, 58% of participants were available for cognitive follow-up. Participants lived near centers in Maryland, North Carolina, Mississippi, and Minnesota suburbs.

Baseline hypertension was associated with cognitive decline of greater magnitude than that experienced in participants who did not have baseline hypertension.

Participants who had JNC-8—specified indications for initiating antihypertensive treatment at baseline experienced greater 20-year declines than those who did not.

Untreated hypertension was associated with the highest risk for cognitive decline. When the researchers compared untreated hypertension’s effect to that of aging alone on cognitive decline, they found that its contribution was relatively modest (6.5% more decline after 20 years) but notable.

Participants who had hypertension and used antihypertensives had less cognitive decline during the 20 years than those who were untreated. Evidence of definitive benefit of antihypertensive treatment would need to be confirmed in randomized clinical trials.

Each 20 mm Hg increment at baseline was associated with an additional decline of 0.048 points in global cognitive z-score in whites but not in African Americans. The authors proposed that bias due to attrition was a primary reason for the relative lack of an observed association between hypertension and cognitive decline in African American participants. Systolic BP at the end of follow-up was not associated with the preceding 20 years of cognitive change in either group.

Evaluating cognitive change instead over time reduced the influence of confounding factors like cultural factors or inherited cognitive ability. Midlife hypertension and elevated midlife (but not late-life) systolic BP was associated with more cognitive decline during the 20 years of the study. Greater decline was found with higher midlife BP in whites than in African Americans.