Cognitive Impairment Evaluated With Vascular Cognitive Impairment Harmonization Standards in a Multicenter Prospective Stroke Cohort in Korea
Background and Purpose—Since the Vascular Cognitive Impairment Harmonization Standards (VCIHS) neuropsychological test protocol was proposed by the National Institute of Neurological Disorders and Stroke and Canadian Stroke Network, no studies have applied this neuropsychological protocol to poststroke survivors in a large-scale, multicenter stroke cohort. We determined the frequency of vascular cognitive impairment (VCI) and investigated the feasibility of using the Korean version of the VCIHS neuropsychological protocol in a multicenter, hospital-based stroke cohort in Korea.
Methods—We prospectively enrolled 620 subjects with ischemic stroke within 7 days of symptom onset among 899 patients who were consecutively admitted to 12 university hospitals in Korea. Neuropsychological assessments using the 60-minute Korean VCIHS neuropsychological protocol were administered at 3 months after stroke.
Results—Of the 620 patients, 506 were followed up at 3 months after stroke. Of these, 353 (69.8%) were evaluated for cognitive function using the 60-minute Korean VCIHS neuropsychological protocol. The frequency of VCI at 3 months was 62.6%: VCI with no dementia in 49.9% and vascular dementia in 12.7%. Old age (P=0.014), poor functional outcomes at 3 months (P=0.029), and stroke subtypes other than small vessel disease (P=0.004) were independent risk factors of VCI.
Conclusions—VCI, evaluated using the Korean VCIHS neuropsychological protocol, is substantial at 3 months after ischemic stroke in Korea. The use of the 60-minute Korean VCIHS neuropsychological protocol was feasible in large-scale multicenter studies.
Several studies have elucidated the frequency and characteristics of cognitive dysfunction in stroke patient cohorts. However, most studies of poststroke cognitive impairment have focused on dementia.1–4 In 2006, the National Institute of Neurological Disorders and Stroke and Canadian Stroke Network proposed the Vascular Cognitive Impairment Harmonization Standards (VCIHS), which could be used to evaluate cognitive dysfunction in potential patients with vascular cognitive impairment (VCI) in multicenter studies.5,6 However, no study has applied this neuropsychological test protocol to poststroke survivors in a large-scale, multicenter stroke cohort. The purpose of this study was to determine the frequency of VCI and to investigate the usefulness of the Korean version of the VCIHS neuropsychological (K-VCIHS-NP) protocol in a multicenter, hospital-based stroke cohort study in Korea.
From October 2007 to August 2008, we screened 899 ischemic stroke patients among who consecutively enrolled to the hospital-based stroke registers of 12 university hospitals in South Korea.7 The ischemic stroke was confirmed by magnetic resonance imaging within 7 days of symptom onset.
Of these patients, a total of 620 were enrolled within 2 weeks after stroke for baseline evaluations. At 3 months after stroke, 506 patients underwent a follow-up evaluation, and 353 patients completed the 60-minute K-VCIHS-NP protocol proposed by the National Institute of Neurological Disorders and Stroke and Canadian Stroke Network (Figure). Korean Mini-Mental Status Examination for evaluating global cognitive dysfunctions and the Informant Questionnaire of Cognitive Decline in the Elderly (IQCODE) for the premorbid history of cognitive dysfunctions were also included. The tests and scales that compose the K-VCIHS-NP protocol were validated and standardized for Korean subjects (online-only Data Supplement Table I).
Dementia was diagnosed with reference to Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, criteria based on cognitive functions that were categorized as impaired when a score was below the 10th percentile for an individual domain and social functioning status as assessed by the Instrumental Activities of Daily Living scale. Patients were classified as having vascular dementia (VaD), VCI with no dementia, and normal cognition. The detailed methodology is described in the online-only Data Supplement.
Of 620 patients enrolled in baseline evaluation, 267 missed the cognitive assessment follow-up at 3 months, as depicted in the Figure. Patients who were lost to follow-up were older, less educated women, and had more hypertension, previous stroke, severe stroke symptoms when admitted, and worse prestroke functional and cognitive status (online-only Data Supplement Table II).
The number of subjects with VCI at 3 months after stroke was 221 (62.6%) of the 353 poststroke survivors who completed the K-VCIHS-NP protocol; VCI with no dementia was apparent in 176 (49.9%), and VaD was apparent in 45 (12.7%). As defined by the Korean Mini-Mental Status Examination scores, the frequencies of VCI with no dementia and VaD were 9.9% (35/353) and 16.4% (58/353), consecutively. The proportion of patients with recurrent stroke who experienced VaD was twice that of first-ever stroke patients (21.5% vs 10.8%; Table). The frequency of prestroke cognitive decline evaluated using Korean-IQCODE at the time of admission was 7.2% (25/346) among patients who completed the 3-month follow-up. The frequency of VaD among patients who had experienced prestroke cognitive decline was 40% (10 of 25), which was ≈4-times higher than the frequency among patients who did not have prestroke cognitive decline (10.3%; 33/321). Old age (P=0.014), poor functional outcomes at 3 months poststroke (P=0.029), and stroke subtypes other than small vessel disease (P=0.004) were independent risk factors of VCI (Online Table III).
To the best of our knowledge, this is the first large-scale, multicenter study to evaluate the frequency of VCI using the 60-minute K-VCIHS-NP protocol proposed by the National Institute of Neurological Disorders and Stroke and Canadian Stroke Network.
A substantial percentage of patients in the prospective acute stroke cohort were unable to undergo cognitive assessment because of death, worsening of neurological or medical conditions, or failure to follow-up. In this study, of the 506 patients who were followed-up at 3 months after stroke, 353 patients (69.8%) were evaluated using the K-VCIHS-NP protocol (Figure). This coverage rate of cognitive assessment was slightly lower than the rates from previous studies, which were reported to be 74.0% to 76.5%.3,4,8 However, the previous cohort studies were not conducted in a multicenter setting, and they applied individual neuropsychological tests, such as the IQCODE or the Mini-Mental Status Examination.2,5–7
A higher frequency of VCI at 3 months (62.6% in poststroke survivors) was observed in this study. When the poststroke cognitive impairments were defined using the Mini-Mental Status Examination, the frequency of VCI was 37.1% (161/434) in a previous cohort study in China8 and 26.4% (93/353) in this study. In another study, ≤55% of the patients showed abnormalities in ≥1 cognitive domain in a complementary neuropsychological battery.9 This disparity might be explained by the differences in study setting and in the extensiveness of the neuropsychological protocols used.2
In this study, of the 346 patients who completed the K-IQCODE at the time of admission, only 25 (7.2%) had experienced cognitive dysfunctions before stroke. Because prestroke cognitive decline had to be retrospectively evaluated using the K-IQCODE in this hospital-based study setting, the prevalence of prestroke dementia could be underestimated. However, the progression of patients from prestroke cognitive decline to VaD observed in this study was similar to that of a previous cohort study.3
In conclusion, the 60-minute K-VCIHS-NP protocol might be useful for evaluating cognitive impairments in poststroke survivors in multicenter cohort studies.
Korean VCIHS study group members include Hee-Jun Bae, Jae-Kwan Cha, Ki-Hyun Cho, Soo-Jin Cho, San Jung, Yeonwook Kang, Dong-Eog Kim, Hahn-Young Kim, Oeun-Kyu Kim, Yong-Jae Kim, Im-Suck Koh, Sun-Uck Kwon, Ju-Hun Lee, Seung- Hoon Lee, Soo-Ju Lee, Mi Sun Oh, Jong-Moo Park, Joon-Hyun Shin, Kyung-Ho Yu and Byung-Chul Lee.
Sources of Funding
This study was supported by a grant from the Korea Healthcare Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (A102065), and Eisai Korea.
The online-only Data Supplement is available at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.112.668343/-/DC1.
- Received June 18, 2012.
- Accepted October 18, 2012.
- © 2013 American Heart Association, Inc.
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