Prevalence of Stroke and Transient Ischemic Attack in Korean Elders
Findings From the Korean Longitudinal Study on Health and Aging (KLoSHA)
Background and Purpose— Studies on the epidemiology of stroke and transient ischemic attack (TIA) are very limited in Asian elderly populations. We investigate the prevalence, risk factors, and neuropsychiatric comorbidities of stroke and TIA in community-dwelling Korean elders.
Methods— Standardized face-to-face interviews, neurological examinations, and physical examinations were conducted in 714 randomly sampled community-dwelling Korean elders aged ≥65 years. Diagnoses of stroke and TIA were made according to the World Health Organization criteria.
Results— Age- and education-standardized prevalences of stroke, TIA, and cerebrovascular disorder (implying stroke or TIA) were estimated to be 10.1%, 8.9%, and 15.4%, respectively, in Korean elders. Hypertension and current smoking were associated with the risk of stroke, whereas atrial fibrillation, high diastolic blood pressure, high serum low-density lipoprotein cholesterol, and hypertension were associated with the risk of TIA. Cerebrovascular disorder was associated with the risk of major depressive disorder, vascular dementia, and nonamnestic mild cognitive impairment (P<0.05).
Conclusion— Prevalences of stroke and TIA in Korean elders were higher than in white elders. Stroke and TIA were associated with increased risk of depression and cognitive disorders.
Although the prevalence of stroke and transient ischemic attack (TIA) in Asians seems to be somewhat different from that in white populations, community-based epidemiological studies on stroke and TIA are very limited in Asian elders.1 In Korea, epidemiological studies on stroke and TIA, which specifically targeted an old population, have not been performed yet. In the present study, we estimated the prevalence of stroke and TIA in Korean elders aged ≥65 years and investigated their risk factors and associated neuropsychiatric disorders.
This study was a part of the Korean Longitudinal Study on Health and Aging.2 A simple random sample (N=1118) was drawn from the roster of 61730 Korean elderly individuals aged ≥65 years who were residents in Seongnam, Korea, on August 1, 2005. All cases were fully informed regarding study participation and provided written informed consent by themselves or by their legal guardians. The study protocol was approved by the Institutional Review Board of Seoul National University Bundang Hospital.
Standardized clinical interviews, neurological and physical examinations, and laboratory tests were conducted by geriatric neuropsychiatrists according to the standardized TIA/stroke form from the Atherosclerosis Risk in Communities Study,3 the protocol of the Korean Version of the Consortium to Establish a Registry for Alzheimer’s Disease clinical assessment battery,4 and the Mini International Neuropsychiatric Interview.5
Stroke and TIA were diagnosed according to the World Health Organization criteria.6 Major psychiatric disorders, including dementia, were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnostic criteria.7 Diagnosis of mild cognitive impairment (MCI) was made according to the consensus criteria from the International Working Group on MCI.8
Prevalence estimates of stroke and TIA with 95% CIs were derived using the exact methods. Standardized prevalence rates were estimated using the direct standardization method. Vascular risk factors among diagnostic groups were compared using analysis of variance and logistic regression analysis. All the statistical analyses were done using the SPSS 15.0 statistical package.
Seven hundred fourteen subjects participated and completed the present study (response rate, 63.9%; age, 71.9±5.7 years; women, 57.8%). The respondents were younger (Quartile 1, 67 years old; median, 71 years old; Quartile 3, 76 years old; χ2=47.579; df=1; P<0.001, Kruskal-Wallis test) and included fewer women (women, 70.8%; P<0.01; χ2 test) than the nonrespondents. Seventy-one met the criteria for stroke (men, 30; women, 41), 61 for TIA (men, 21; women, 40), and 24 for cerebrovascular disease (CVD; implying stroke or TIA; men, 9; women, 15).
Age- and education-standardized prevalence estimates for stroke, TIA, and CVD in Korean elders aged ≥65 years were 10.1% (95% CI, 7.9% to 12.4%), 8.9% (95% CI, 6.8% to 10.9%), and 15.4% (95% CI, 12.7% to 18.0%), respectively. The prevalence of CVD reached a peak at the age of 75 to 79 years old and then declined after age ≥80 years. Prevalence estimates for stroke, TIA, and CVD did not differ by gender (P>0.1; Table 1).
Hypertension (P=0.011) and current smoking (P=0.029) were statistically associated with stroke. Atrial fibrillation (P<0.001), hypertension (P=0.031), serum low-density lipoprotein cholesterol (P=0.046), and diastolic blood pressure (P=0.035) were statistically associated with TIA (Table 2).
CVD was associated with the risk of vascular dementia (P<0.001) and nonamnestic MCI (P=0.011), whereas it was not associated with that of Alzheimer disease or amnestic MCI (P>0.1). CVD was also associated with the risk of major depressive disorder (P=0.034; Table 3).
This is the first study on the prevalence of stroke and TIA in the Korean elderly population. Although direct international comparison of stroke prevalence is not easy, the prevalence of stroke and TIA in Asian elders seemed to be higher than those in white elders, which may be related to a combined effect of genetic and environmental factors.1
The prevalence estimates of stroke and TIA increased until 75 to 79 years old and then decreased thereafter, which was consistent with previous observations.9 Either low survival rate or selection bias due to stroke-related physical disabilities may contribute to the decrease of stroke and TIA prevalence in the oldest age group. Although stroke and TIA have been reported to be more prevalent in men than in women,1 such a gender difference was not found in our sample.
In the hospital-based Korean Stroke Registry, hypertension (65.4%) was the most common risk factor of acute stroke in Koreans followed by smoking (34.5%).10 Both hypertension and current smoking were also found to be significant risk factors for stroke in our elderly population. Atrial fibrillation was associated with TIA but not with stroke in our sample, which could be partly attributed to some age-dependent changes in the association of atrial fibrillation with stroke and TIA.11
Although CVD has been proposed as a precursor to Alzheimer disease in several studies,12 CVD was not associated with the risk of Alzheimer disease and amnestic MCI in the present study, which warrants further investigations on the role of CVD in the pathogenesis of Alzheimer disease.
A strength of this study was that all the participants were assessed by expert physicians and conformed to standardized and structured instruments. Also, combining stroke and TIA allowed for more generalizable results to patients with symptomatic CVD. However, subtypes of stroke were not specified, statistical power was limited due to small sample size, and the respondents were younger and had more men than the nonrespondent group.
Sources of Funding
This work was supported by an Independent Research Grant from Pfizer Global Pharmaceuticals (Grant No. 06-05-039) and a Grant for Developing Seongnam Health Promotion Program for the Elderly from Seongnam City Government in Korea (Grant No. 800-20050211).
- Received May 5, 2008.
- Revision received June 16, 2008.
- Accepted June 26, 2008.
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