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Higher Diastolic, Not Systolic, Blood Pressure Linked to Impaired Cognition

Higher diastolic blood pressure (DBP) levels, but not systolic blood pressure (SBP) levels, can impair cognitive status in individuals without prior history of stroke or transient ischemic attack, according to the results of a large study. So being more aggressive in the treatment of hypertension can possibly prevent dementia.

Georgios Tsivgoulis, M.D., from the Comprehensive Stroke Center at the University of Alabama in Birmingham, writes, “Although both higher [pulse pressure] and SBP values were related to cognitive impairment in unadjusted analyses, these associations were no longer significant after accounting for demographics, health behaviors, and vascular risk factors.”

“The present study indicates that elevated [DBP] levels are linearly and cross-sectionally associated with a higher likelihood of impaired cognitive status. If this association is causally established in future longitudinal studies, than reducing elevated BP levels may result in reducing the incidence of dementia,” Dr. Tsivgoulis told Medscape Neurology.

The study authors write that the prevalence of dementia is estimated at approximately 8% and the prevalence of hypertension approximately 65% among individuals aged 65 years or older. Although the relationship among BP, cognitive function, and dementia has received a lot of attention in recent years, the findings have varied greatly.

In this study, the investigators sought to evaluate the cross-sectional relationship of BP components (SBP, DBP, and pulse pressure) with cognitive impairment after adjusting for potential confounders.

Dr. Tsivgoulis looked at data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a national, population-based, longitudinal cohort study evaluating stroke risk in 30,228 black and white men and women aged 45 years or older.

From REGARDS, the investigators selected 19,836 participants (mean age, 64.6 years; 57.7% white, 60.8% female), who were enrolled from December 2003 to March 2007, had no prior history of stroke or transient ischemic attack, and completed baseline home physical evaluations.

During the in-home visit, BP measurements were taken as the average of 2 measurements using a standard aneroid sphygmomanometer.

At the end of the study, results showed that higher DBP levels were associated with impaired cognitive status after adjusting for demographic and environmental characteristics, risk factors, depressive symptoms, and antihypertensive medications. An increment of 10 mm Hg in DBP was associated with 7% (95% confidence interval [CI], 1% – 14%; P = .0275) higher odds of cognitive impairment.

However, no independent association was identified between impaired cognitive status and SBP (odds ratio [OR], 1.02; 95% CI, 0.99 – 1.06) or pulse pressure (OR, 0.99; 95% CI, 0.95 – 1.04).

Dr. Tsivgoulis stated that, “We were surprised by the fact that DBP and not SBP or [pulse pressure] was related to cognitive impairment after adjusting for potential confounders…. We attributed these intriguing findings to a potential association between diastolic hypertension and accelerated stiffening of cerebral small vessels that are profoundly affected by DBP.”

“These vascular changes…result in a reduction of luminal diameter, which in turn causes increased resistance to flow and decline in cerebral perfusion. Such hypoperfusion may produce discrete regions of small cerebral infarctions and diffuse ischemic changes in the periventricular and deep white matter (leukoaraiosis), causing vascular cognitive impairment and also contributing to the pathogenesis of Alzheimer’s disease by destabilizing neurons and synapses,” the authors write.

The results showed no evidence of nonlinear relationships between any of the BP components and impaired cognitive status and no interaction between age and the relationship of impaired cognitive status with SBP (P = .827), DBP (P = .1333), or pulse pressure (P = .827) levels. Also, no interaction was identified between race and the relationship of impaired cognitive status with SBP (P = .899), DBP (P = .966), or pulse pressure (P = .858) levels. 

“Our study showed that higher DBP levels were independently related to a higher likelihood of impaired cognitive status in a large national sample that was nearly balanced with respect to race and gender,” said Dr. Tsivgoulis. However, he added, the linear, cross-sectional association needs to be confirmed in a longitudinal analysis. 

Neurology. August 25,2009;73:589–595.