Brain atrophy is promoted by both high and low blood pressure

Brain atrophy, with progressive cognitive impairment, can include among causal factors neuronal loss due to diminished oxygen perfusion. Earlier posts have documented the importance of not over-medicating hypertension. A study just published in JAMA Neurology provides evidence that brain atrophy is promoted by low diastolic blood pressure in addition to hypertension. The authors note that...

"Studies have shown that both high and low blood pressure (BP) may play a role in the etiology of brain atrophy. High BP in midlife has been associated with more brain atrophy later in life, whereas studies in older populations have shown a relation between low BP and more brain atrophy. Yet, prospective evidence is limited, and the relation remains unclear in patients with manifest arterial disease."

So they investigated the associations of baseline blood pressure changes in BP over time with the progression of brain atrophy by examining data for 663 patients over almost four years. In addition to blood pressure their measurements included brain parenchymal fraction, cortical gray matter fraction, and brain ventricular fraction as metrics for the progression of global, cortical, and subcortical brain atrophy. Clinicians who manage blood pressure should take note of their findings:

"Multivariable adjusted regression analysis showed that patients with lower baseline diastolic BP (DBP) or mean arterial pressure had more progression of subcortical atrophy... Furthermore, in patients with higher baseline BP (DBP, mean arterial pressure, or systolic BP), those with declining BP levels over time had less progression of subcortical atrophy compared with those with rising BP levels."

How should we make practical use of these results? As the authors state in their conclusion, hypertension should be managed appropriately but caution must be taken in lowering blood pressure when the diastolic measurement is already on the low side:

"In patients with manifest arterial disease, low baseline DBP was associated with more progression of subcortical atrophy, irrespective of the BP course during follow-up. Furthermore, in patients with higher baseline BP, declining BP levels over time were associated with less progression of subcortical atrophy. This could imply that BP lowering is beneficial in patients with higher BP levels, but caution should be taken with further BP lowering in patients who already have a low DBP."