Epidemiology of stroke and its subtypes in Chinese populations
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Background: Chinese populations have been reported to have a higher stroke incidence as well as different stroke epidemiology compared with white populations. However, reliable comparisons have been precluded by a lack of methodologically robust studies. I aimed to systematically evaluate the incidence of stroke, the distribution of its main types/subtypes, and risk factor distributions among stroke types/subtypes in Chinese, and to compare these with data from white populations. Methods: I performed a series of systematic reviews and meta-analyses of studies conducted since 1990 which had data on (1) incidence of stroke, (2) pathological types of stroke or ischaemic stroke subtypes, and (3) frequency of risk factors among pathological types of stroke or ischaemic stroke (IS) subtypes in Chinese populations, and in white populations for comparison. I calculated age-standardized stroke incidence and the proportions of each pathological type and ischaemic subtype. For each risk factor, I calculated study-specific and pooled odds ratios (ORs) using a random effects model for intracerebral haemorrhage (ICH) versus IS, for each IS subtype versus other subtypes, and for overall IS patients, comparing findings for Chinese versus Whites. In addition, I conducted individual patient analyses of data from the National Taiwan University Hospital (NTUH) Stroke Registry, which consecutively recruited 6675 acute stroke patients from 2006-2011, comparing risk factor profiles among stroke types and subtypes and using logistic regression to adjust for potential confounding factors. Results: From my systematic reviews, I found a younger onset of stroke, a slightly higher overall stroke incidence and higher proportion of ICH in Chinese versus white populations. Although the overall proportion of lacunar infarct appeared higher in Chinese from hospital-based studies than white populations, confirming the different distributions of ischaemic subtypes will need further comparable population-based studies. In my meta-analyses comparing risk factors for ICH versus IS, in Chinese - but not Whites – hypertension (HTN) and alcohol intake were significantly more frequent, while mean age was lower in ICH than IS. In IS, the overall prevalence of hypertension, diabetes, smoking, and alcohol intake were similar between Chinese and white IS patients, whereas hypercholesterolaemia, ischaemic heart disease (IHD) and atrial fibrillation (AF) were less common in Chinese IS patients. As for IS subtypes, the relative frequencies of risk factors were mostly qualitatively similar (although different in size) in Chinese and white populations. Compared with other ischaemic subtypes: large artery atherosclerosis (LAA) strokes were associated with diabetes; cardioembolic (CE) strokes were associated with AF and IHD; small vessel disease (SVD) strokes or lacunar strokes were associated with hypertension and diabetes. Analyses of NTUH individual patient data showed that HTN and alcohol intake were independent risk factors for ICH versus IS in a Chinese population in Taiwan, regardless of age, sex, or other risk factors. The results were consistent with my previous risk factor meta-analyses for ICH versus IS. In IS analyses, the prevalence of hypertension, diabetes, AF, and hyperlipidaemia in overall IS patients based in Taiwan were higher than the pooled results in my risk factor meta-analysis for IS for all Chinese populations including mainland China. In terms of risk factor associations with IS subtypes, the findings after controlling for potential confounders were mostly close to my previous meta-analysis results with the exception of stronger associations of hypertension and diabetes with SVD (lacunar) strokes. Conclusion: I have shown a younger onset of stroke, a higher overall stroke incidence, an around twofold higher proportion of ICH and different distribution of IS subtypes, as well as some differences in risk factor distributions among pathological types of stroke and IS subtypes in Chinese compared with white populations. My results help to inform us of different stroke mechanisms in different populations, to guide further well-designed research in this area, and to direct better strategies for stroke prevention in Chinese populations.