What's the science?

Hypertension is known to be associated with stroke, however, it’s still unclear how blood pressure is related to stroke and brain infarcts (tissue injury occurring as a result of stroke). Brain infarcts are common in aging and often go undetected. Evidence for the association between blood pressure and infarcts is mixed, and further, no one has investigated whether blood pressure in late life is associated with neurodegenerative diseases like Alzheimer’s disease. Recently in Neurology, Arvanitakis and colleagues test whether blood pressure in late life is associated with brain infarcts and Alzheimer’s disease.

How did they do it?

1288 elderly adults completed a longitudinal study of aging (8-year follow-up). Systolic and diastolic blood pressure were recorded at baseline and annually throughout the study. The authors measured the mean blood pressure as well as the rate of change in blood pressure over time. History of medications and diseases were collected. Brains were assessed for neuropathology post-mortem (after autopsy). This assessment identified cerebrovascular disease (infarcts) using gross examination, microinfarcts with staining, atherosclerosis with vessel examination and arteriosclerosis with tissue staining. They also examined neurodegenerative pathology, including amyloid-beta plaques and neurofibrillary tangles.

What did they find?

Risk of having one or more brain infarcts was higher in individuals with a higher systolic blood pressure (46% increased risk of one or more infarcts on average for an individual who was 1 standard deviation above the mean systolic blood pressure). Higher mean systolic blood pressure was associated with a greater risk of gross infarcts and micro-infarcts. The more rapid the decline in blood pressure over time, the greater the risk of developing one or more infarcts was. Individuals with a higher mean systolic blood pressure also had higher degrees severity of atherosclerosis and arteriosclerosis. Mean diastolic blood pressure was associated with brain infarcts, however the rate of decline was not. Using a linear regression model, they found that higher systolic blood pressure was associated with a higher number of neurofibrillary tangles (Alzheimer’s disease pathology), but was not associated with changes in amyloid plaque pathology. There was no relationship between rate on decline in systolic blood pressure and Alzheimer’s disease pathology.