Longitudinal systolic blood pressure characteristics and integrity of white matter tracts in a cohort of very old black and white adults

Background: We sought to determine which systolic blood pressure (SBP) characteristics are associated with reduced brain integrity and whether these associations are stronger for white or gray matter. We hypothesized that exposure to higher and variable SBP will be associated with lower structural integrity of both gray and white matter.

Methods: Neuroimaging, SBP, and cognition were obtained in 311 community-dwelling adults in 2006-2008 (average age = 83 years; 58% women; 40% black). Antihypertensive medications, SBP, and health-related factors were collected from 1997 to 1998 to time of neuroimaging. SBP values obtained from 1997 to 1998 to time of neuroimaging were used to compute mean; pulse pressure; coefficient of variation; and peak, load, and group-based trajectories.

Results: Higher mean SBP was associated with lower white matter integrity in uncinate and superior lateral fasciculi bilaterally, independent of age, stroke history, antihypertensive medication use (odds ratio of having white matter hyperintensities greater than or equal to the median for 10mm Hg of SBP = 10.4, 95% confidence interval = 10.2-10.6, P = 0.0001; standardized beta for fractional anisotropy = -13.54, SE = 4.58, P = 0.003). These neuroimaging markers attenuated the association between higher SBP and lower digit symbol substitution test. Results were similar for trajectories of SBP and stronger for those with previously higher and variable SBP even if SBP was normal at neuroimaging. Results were similar for those without stroke. Associations with gray matter measures were not significant.

Conclusions: If confirmed, these data suggest a history of higher and variable SBP for very old adults may be useful to alert clinicians to potential lower integrity in selected tracts, whereas cross-sectional SBP measurements may obscure the risk of underlying white matter hyperintensities. Whether lowering and/or stabilizing SBP levels in very old adults without a remarkable cardiovascular history would have neuroprotective effects and reduce dementia risk needs further study.