Poststroke Cognitive Impairment:Cognitive Assessment And Risk Factors

Background and Purpose:Vascular cognitive impairment (VCI) affects two thirds stroke patients. To develop a consensus in neuropsychological evaluation of VCI. the National Institute of Neurological Disorders and Stroke and the Canadian Stroke Network (NINDS-CSN) recommended a neuropsychological battery of three protocols to diagnose VCI, and suggested generalization in different languages and cultures. Currently, Korean, Hong Kong, Singapore and France have validated these protocols in stroke or transient ischemic attack patients. However, there is no validation study for a Mandarin Chinese version. Hence, we developed a Mandarin adaption for the NINDS-CSN battery, and aimed to investigate the external validity and reliability of the Mandarin protocols. Besides, we evaluated the effect of different operational VCI definitions on measured incidences of post-stroke cognitive impairment, and validated the cognitive screening tests (face-to-face and telephone assessments) in post-stroke patients. Finally, we analyzed the risk factors related to poststroke cognitive impairment.Methods:The NINDS-CSN protocols were adapted into Mandarin Chinese, and the validity and reliability of the Mandarin version were determined. External validity, defined as the ability of the protocol summary scores to differentiate stroke patients from controls, was determined using the area under the curve (AUC) of the receiver operating characteristics curve. We also evaluated internal consistency and intra-rater reliability, by Cronbach’s a and intraclass correlation coefficients (ICC), respectively. Based on the validated Mandarin version, different operational definitions (>1,>1.5 and>2 standard deviations, SD) of control means were compared together with the use of single versus multiple tests to define domain impairment. Meanwhile, we validated the cognitive screeners, mini-mental state examination (MMSE) and Montreal cognitive assessment (MoCA) as face-to-face tests, and the 5 min protocol together with six item screener (SIS) as telephone tests, in screening cognitive impairment in stroke patients. Best cut-off values were chosen referring to the highest Youden index. Stroke patients with and without VCI were compared with respect to epidemiological, clinical, and neuroimaging data (number, size and location of acute infarcts and lacunes, severities of white matter hyperintensities and brain atrophy). Univariate and logistic regression analyses were utilized to determine risk factors of poststroke cognitive impairment.Results:The validation of the Chinese version was based on fifty mild stroke patients and 50 stroke-free normal controls. External validity evaluated by AUCs was 0.88 (95% confidence interval [CI],0.82-0.95),0.88 (95% CI,0.81-0.95), and 0.86 (95% CI, 0.79-0.93) for the 60-min,30-min and 5-min protocols, respectively. Cronbach’s alpha of the cognitive tests was 0.87 for all subjects. Intra-rater reliability was acceptable with intraclass correlation coefficients 0.90,0.83 and 0.75 for the 60-min, 30-min and 5-min protocols, respectively. For the validation of telephone tests, eighty-nine patients (age,62.9±8.6 years; male,65.2%) received a face-to-face assessment and 80 completed telephone tests at least one month later. Rates of cognitive impairment ranged from 46.3% at>2 SD cut-off to76.3% at>1 SD cut-off; while the amnestic single-domain impairment was relatively rare irrespective of various definitions. More stringent definitions resulted in lower incidence of cognitive impairment, and patients were more likely to be classified as single domain impairment. Screening tests of face-to-face evaluation and telephone evaluation all indicated good external validity (AUC>0.7) under different definitions. As face-to-face tests, MoCA showed better agreement with the comprehensive cognitive assessments than MMSE, and the optimal cut-off for MMSE was≤27 and for MoCA was≤19. The time required to administer telephone tests was 4.3±1.0 minute for the 5 min protocol and 57.3±17.7 seconds for SIS. Compared to the SIS, the 5 min protocol was better in agreement with the comprehensive cognitive assessments, and the optimal cut-off was<23 for the 5 min protocol and<4 for SIS. To explore the risk factors of poststroke cognitive impairment, sixty-eight consecutive patients (age,62.7 ±8.8 years; female,36.8%) were recruited at a median interval of 7 months after stroke onset, and 42 (61.8%) patients were diagnosed with cognitive impairment based on a validated 60-min neuropsychological battery. Cognitively impaired patients were less educated (P<0.001), more likely to be female (P=0.001), described higher apathy (P=0.008) and more old infarcts (P=0.046) than cognitively normal patients. Binary logistic regression showed that educational level (adjusted odds ratio [OR] 0.728,95% CI,0.575-0.922;P=0.008), female sex (adjusted OR 6.477,95% CI, 1.275-32.902;P=0.024), the apathy score (adjusted OR 0.905,95% CI,0.823-0.995, P=0.039), and global cortical atrophy (adjusted OR 6.131,95% CI,1.351-27.828, P=0.019) were factors independently associated with cognitive impairment in post-stroke patients.Conclusions:The adapted Chinese versions of three NINDS-CSN neuropsychological protocols were valid and reliable for assessing poststroke cognitive impairment in Chinese patients with mild stroke. Within established criteria, differences in operational methodology resulted in 1.6-fold variation of cognitive impairment estimation. Face-to-face tests of MMSE and MoCA, together with the 5 min protocol and SIS as telephone instruments, were all effective cognitive screening tools for stroke patients, and the practicable cutoffs of cognitive impairment were 27 19,23 and 4 points, accordingly. Lower educational level, female sex, apathy symptoms and global cortical atrophy were independent risk factors associated with cognitive impairment in stroke patients.