Premature vascular aging in precipitous stroke in a middle-income country

Mabena, Philanathi
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Stroke often occurs over a younger adult age range in low to middle-income countries. As standard risk prediction strongly depends on age, the ability to detect the risk of stroke over this younger adult age using this approach alone may therefore be limited. Although the assessment of carotid intima media thickness (IMT) or plaque presence may add to risk prediction, the efficacy of these assessments in detecting stroke risk at a younger adult age is unknown. In the present study, I compared carotid IMT and plaque (B-mode ultrasound employing a linear array 7.5MHZ probe) in 164 patients of African ancestry (age ≥18 years) with a new stroke to that in 430 age-and-sex matched-controls (age ≥16 years) of African ancestry from a community sample. 96 (58.5%) of the stroke sample were of an age where the event would be considered as premature (<55 years in women and <50 years in men). Although hypertension and a decreased HDL cholesterol concentration were associated with stroke at a younger adult age, more than 50% of participants with stroke at this age had either no risk factor or a single risk factor. As compared to at an older age, a lower prevalence of small-vessel disease, higher prevalence of stroke of other determined aetiology and lack of detection of atherosclerotic strokes was noted at a younger age. Cardioembolic stroke accounted for 20% of all strokes with a similar prevalence in both young and old age categories. In unadjusted or multivariate adjusted models, carotid IMT was increased over most of the adult lifespan in those with stroke as compared to controls at the same age. However, in stepwise regression models, carotid IMT was independently associated with stroke at an older (p<0.0001) but not younger (p=0.17) age, whereas plaque was independently associated with stroke at both a younger (p<0.0001) and older (p<0.0001) age. Moreover, in the same regression model, plaque (p<0.0001) but not IMT (p=0.82), was independently associated with stroke at a younger age while IMT (p<0.0001) and plaque (p=0.004) were both independently associated with stroke at an older age. Moreover, plaque showed a greater performance than IMT for stroke detection over a younger age range. In conclusion, stroke is frequently premature in groups of African ix ancestry in South Africa and this is often associated with an unremarkable conventional risk factor score. While non-invasive assessments of carotid artery plaque are strongly and independently associated with stroke over the young adult age range, IMT is not. The assessment of carotid plaque may be an essential tool for predicting the risk of premature stroke in Africa
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Medicine to the Faculty of Health Sciences, School of Physiology, University of the Witwatersrand, Johannesburg, 2020