P3–199: Systolic blood pressure and double product are associated with reduced hippocampal volume in the Alzheimer's Disease Neuroimaging (ADNI) study

A few longitudinal studies emphasized that high blood pressure in midlife promoted dementia in late life. Though the mechanisms for the effects remain poorly understood, systolic (SBP) and pulse pressure (PP) have been demonstrated to associate with medial temporal lobe atrophy (MTA), in one study. These reports support growing evidence that hypertension in midlife may catalyze dementia in late life, especially when co-existing with white matter changes. Because the optimal blood pressure (BP) for enhanced cognition remains poorly defined, there is now an urgent need to further delineate the role of BP in AD. We examined the relationship of BP to hippocampal volume in the ADNI data, yet the most robust longitudinal data to date. An exhaustive list of publications detailing the ADNI methods is currently available elsewhere. The DANI data used in this analysis were downloaded on October 10, 2012. Initially we used Univariate analysis to examine the data. Where appropriate, Proc GLM (General Linear Model), and Multiple Logistic Regression analyses were used to discern the relationships of BP to hippocampal volume, and the LSMeans in GLM to estimate mean values. All analyses were performed in the Statistical Analysis System (SAS), Research Triangle North Carolina. Of the 1210 subjects initially examined for these analyses, 558 and 240 subjects had complete data on important covariates at 2 and 4 years follow-up, respectively. In our final model that adjusted for age, gender education and ethnicity, increased double product (SBP * heart rate) a measure the heart's work load and SBP, related to reduced hippocampal volume at 24 months and 48 months, respectively (all P < 0.05). We concluded that SBP and double product were associated with reduced hippocampal volume in the ADNI study. Even if better control of BP translates into very small improvements in cognition, substantial gains might be realized given the total number of persons with hypertension in the United States.