Kara Jo Swafford, MD
Poststroke cognitive impairment (PSCI) is common, having a prevalence between 24% and 58% at 3 months following the acute event. Symptoms can range from mild cognitive impairment to severe dementia and is associated with higher morbidity and mortality. Patient demographics, vascular risk factors and stroke subtypes may help predict development of PSCI.
Hypertension is an important factor that increases the risk for PSCI by causing cerebrovascular dysautoregulation, leading to impaired cortical function. Hypotension can also worsen prognosis, leading to impairment of cognition by reducing cerebral blood flow. This suggests a U-shaped relationship between blood pressure and stroke outcome. Regulation of blood pressure is vital for cerebral perfusion and preventing further neuronal injury. This is why identifying the optimal blood pressure range becomes important in the early phase after ischemic stroke. There is, however, no clear consensus on optimal blood pressure levels to reduce the risk of PSCI. There are also little data on how stroke subtypes relate to PSCI.
He et al provide an enlightening article investigating the relationships between early poststroke blood pressure control and stroke subtype and the risk of developing PSCI. Their single-center prospective cohort study included patients presenting within 24 hours of a first-ever acute ischemic stroke who had a systolic blood pressure (SBP) ≥ 140 mmHg and diastolic blood pressure (DBP) ≥ 90 mmHg. Patients who had a decreased level of consciousness, modified Rankin Scale score > 1 prior to stroke onset, severe mental disorder or dementia and aphasia were excluded.
Blood pressure measurements were assessed over the first 7 days after stroke onset, defined as the early phase. Blood pressure was treated according to the 2013 American Heart Association/American Stroke Association guidelines and the 2013 European Society of Hypertension/European Society of Cardiology guidelines. Acute ischemic stroke was categorized into five subtypes based on the Trial of ORG 10172 in Acute Stroke Treatment classification (large artery atherosclerosis (LA), cardioembolism, small artery occlusion (SA), other determined cause and undetermined cause) and into four subtypes according to the Oxfordshire Community Stroke Project classification (lacunar infarct, total anterior circulation infarct (TACI), partial anterior circulation infarct and posterior circulation infarct).
Cognitive assessments were completed by a trained neurologist using the Montreal Cognitive Assessment (MoCA). Patients were considered to have cognitive impairment with MoCA scores < 26 with ≥ 12 years of education and < 27 with < 12 years of education. The Hamilton Depression Scale-24 was used to help exclude the influence of poststroke depression on cognitive impairment. Participants were followed up at 14 days, 3 months, 6 months and 12 months poststroke.
Patients were divided into quintiles (Q1-Q5) based on blood pressure in the early phase. No significant differences were found regarding demographics, vascular risk factors, family history and stroke features. MoCA scores were not different among quintiles after admission and at 14 days based on blood pressure in the early phase. MoCA scores in Q3 (SBP 143-158 mmHg or DBP 93-102 mmHg) were highest at 3 and 6 months, but not at 12 months. Q1 patients (SBP 102-127 mmHg or DBP 66-82 mmHg) and Q5 (SBP 171-215 mmHg or DBP 110-138 mmHg) had the highest risk of PSCI at 3 months.
LA and TACI subtypes were associated with elevated risk of PSCI after 2 weeks, peaked at 3 months and cognitive function gradually recovered until 12 months. These subtypes are most commonly caused by occlusion of the middle cerebral or anterior cerebral artery and lead to large infarcts in the frontal, parieto-occipital and temporal areas. It can be concluded that large stroke volumes in these cortical regions are associated with increased risk of PSCI. In the SA subtype, visuo-executive function, attention and delayed recall were particularly reduced at 3 months.
This study showed that extremes of blood pressure are associated with increased risk of PSCI at 3 months, and maintaining SBP/DBP 143-158/93-102 mmHg may reduce this risk. It also suggested that larger cortical infarcts increase the risk of PSCI. Limitations include the single center design, small sample size and short follow-up period. Antihypertensive treatments varied among patients due to blood pressure levels and comorbid conditions. A proportion of patients could not complete the MoCA score, and some were lost to follow-up, which may have contributed to selection bias.