Contributions of Cerebral Blood Flow to Associations Between Blood Pressure Levels and Cognition The Age, Gene/Environment Susceptibility-Reykjavik Study

Cerebral hypoperfusion leads to adverse sequalae including dementia. Midlife higher blood pressure (BP) can lead to low cerebral blood flow (CBF), but older persons may need higher BP to maintain cerebral perfusion. We investigated the associations among late-life BP, CBF, and cognition. Data are from 2498 participants with a mean age of 79.8 (SD, 4.7) years of the second exam of the AGES (Age, Gene/Environment Susceptibility)-Reykjavik Study. BP was measured, and phase-contrast (PC) magnetic resonance imaging was acquired to estimate total brain CBFPC. Cognitive outcomes included verbal and working memory, processing speed, mild cognitive impairment, and all-cause dementia. Relationships among late-life BP, CBFPC, and cognition were assessed with regression models, controlling for socio-demographics, BP level at midlife (at a mean age of 49.6 [SD, 5.9] years), cardiovascular factors, and total brain volume. In fully adjusted models, each mm Hg increase in late-life diastolic BP was associated with a -0.082 mL/min per 100 mL (95% CI -0.123 to -0.041) lower CBFPC. In contrast, each mm Hg increase in late-life systolic BP or pulse pressure was associated with a 0.027 mL/min per 100 mL (95% CI, 0.0065-0.048) and 0.061 mL/min per 100 mL (95% CI, 0.038-0.084) higher late-life CBFPC, respectively. Higher CBFPC was significantly related to higher cognitive scores for psychomotor speed, verbal, and working memory and to a lower odd of mild cognitive impairment or dementia, irrespective of late-life BP level. Higher late-life diastolic BP and systolic BP were differentially associated with CBFPC. Our findings suggest CBF is an important correlate of late-life cognition, independent of BP level.

Automated summary

Late-life diastolic blood pressure was negatively associated with cerebral blood flow, while late-life systolic blood pressure and pulse pressure were positively associated. Higher cerebral blood flow was related to better cognitive performance and lower risk of mild cognitive impairment or dementia.