Premature vascular aging in precipitous stroke in a middle-income country
Date
2020
Authors
Mabena, Philanathi
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Abstract
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
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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
Description
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