Cerebrovascular Reactivity and Autoregulation Impairment as a Mechanism of Cognitive Decline in Adults with Uncontrolled Hypertension in Kano, North West Nigeria

Background: Hypertension is the dominant risk factor for stroke and vascular cognitive impairment in Nigeria. Impaired cerebrovascular autoregulation and reduced cerebrovascular reactivity to carbon dioxide represent physiological mechanisms linking chronic elevated blood pressure to white matter disease and cognitive decline. These mechanisms have never been directly measured in Nigerian hypertensive adults. Objectives: This study aims to use transcranial Doppler ultrasonography to characterise cerebrovascular autoregulation using the thigh-cuff deflation method and cerebrovascular reactivity to hypercapnia in adults with uncontrolled hypertension versus well-controlled hypertensive and normotensive comparators at Aminu Kano Teaching Hospital, and to model their relationships with white matter hyperintensity burden and cognitive performance. Methods: Forty uncontrolled hypertensives, forty well-controlled hypertensives, and twenty normotensive controls will be recruited. Transcranial Doppler cerebrovascular autoregulation and reactivity measurements will be performed using validated protocols. Cognitive function will be assessed by the Montreal Cognitive Assessment and digit span tests. Brain magnetic resonance imaging will quantify white matter hyperintensity volume. Multivariate regression and mediation analysis will model pathways from blood pressure control through cerebrovascular physiology to cognition. Expected Outcomes: Uncontrolled hypertensives are hypothesised to exhibit significantly impaired autoregulation indices and reduced cerebrovascular reactivity, with these physiological deficits partially mediating the relationship between uncontrolled hypertension and cognitive impairment. Conclusion: This study will contribute original cerebrovascular physiology evidence to guide hypertension control policies aimed at preventing vascular dementia in Nigeria. Keywords: cerebrovascular autoregulation, hypertension, cognitive decline, transcranial Doppler, Kano.