Abstract
BackgroundStroke incidence is increased in Black individuals but the reasons for this are poorly understood. Exploring the differences in aetiological stroke subtypes, and the extent to which they are explained by conventional and novel risk factors, is an important step in elucidating the underlying mechanisms for this increased stroke risk.MethodsBetween 1999 and 2010, 1200 black and 1200 white stroke patients were prospectively recruited from a contiguous geographical area in South London in the UK. The Trial of Org 10172 (TOAST) classification was used to classify stroke subtype. Age- and sex-adjusted comparisons of socio-demographics, traditional vascular risk factors and stroke subtypes were performed between black and white stroke patients and between Black Caribbean and Black African stroke patients using age-, sex-, and social deprivation-adjusted univariable and multivariable logistic regression analyses.ResultsBlack stroke patients were younger than white stroke patients (mean (SD) 65.1 (13.7) vs. 74.8 (13.7) years). There were significant differences in the distribution of stroke subtypes. Small vessel disease stroke was increased in black patients versus white patients (27 % vs. 12 %; OR, 2.74; 95 % CI, 2.19–3.44), whereas large vessel and cardioembolic stroke was less frequent in black patients (OR, 0.59; 95 % CI, 0.45–0.78 and OR, 0.61; 95 % CI, 0.50–0.74, respectively). These associations remained after controlling for traditional vascular risk factors and socio-demographics. Black Caribbean patients appeared to have an intermediate risk factor and stroke subtype profile between that found in Black African and white stroke patients. Cardioembolic stroke was more strongly associated with Black Caribbean ethnicity versus Black African ethnicity (OR, 1.48; 95 % CI, 1.04–2.10), whereas intracranial large vessel disease was less frequent in Black Caribbean patients versus Black African subjects (OR, 0.44; 95 % CI, 0.24–0.83).ConclusionsClear differences exist in stroke subtype distribution between black and white stroke patients, with a marked increase in small vessel stroke. These could not be explained by differences in the assessed traditional risk factors. Possible explanations for these differences might include variations in genetic susceptibility, differing rates of control of vascular risk factors, or as yet undetermined environmental risk factors.
Highlights
Stroke incidence is increased in Black individuals but the reasons for this are poorly understood
Stroke in black individuals remains a important public health concern as temporal analyses in both the USA and UK suggest that, while stroke incidence is declining in white populations, a similar decline is not occurring in black populations [2, 6]
Age- and sex-adjusted analyses showed that black patients were more likely to have hypertension, diabetes, increased body mass index (BMI) and increased levels of socioeconomic deprivation compared to white patients, but were less likely to have hypercholesterolaemia, ischaemic heart disease, peripheral vascular disease or atrial fibrillation and were less likely to be smoking (Table 3)
Summary
Stroke incidence is increased in Black individuals but the reasons for this are poorly understood. Stroke incidence is increased in European and US black individuals compared to white individuals [2, 3]; age-adjusted incidence has been estimated to be between 2.2 and 2.4 times higher compared with white individuals, with differences being marked at younger ages [2]. The reasons for this increase remain incompletely explained. Stroke in black individuals remains a important public health concern as temporal analyses in both the USA and UK suggest that, while stroke incidence is declining in white populations, a similar decline is not occurring in black populations [2, 6]
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