Blood pressure reduction for vascular risk: is there a price to be paid?
The importance of lowering blood pressure (BP) in hypertensive subjects is well-known and recent studies suggest that lowering of BP in patients who may already be in the normotensive range further reduces the risk of vascular events, particularly stroke. Epidemiological data have also shown that lower BP and antihypertensive treatment may be associated with cognitive impairment once cerebrovascular disease is established. However, the relationship between hypertension and cerebrovascular disease is more complex than suggested by epidemiological or intervention studies. Cerebral imaging studies have shown that cerebral blood flow (CBF) is reduced in areas of small-vessel disease (SVD) and the degree of hypoperfusion correlates with disease severity. Furthermore, impaired neuropsychological performance has been found to correlate with cerebral hypoperfusion in patients with established SVD. These findings raise questions surrounding the desirability of lowering of BP beyond a certain level in such patients. It is conceivable that indiscriminate BP reduction may compromise cerebral perfusion and function in these patients, increasing the risk of cognitive decline and cerebrovascular disease progression. Randomized clinical trials addressing the relationship between antihypertensive treatment and vascular cognitive impairment are lacking. Further studies are therefore needed to assess the cognitive consequences of BP reduction in people with established cerebrovascular disease. This will help to direct appropriate protective strategies and treatments in a vulnerable group of people, many of whom have hypertension and cerebrovascular disease at the same time.