2011 John Wiley & Sons A ⁄ S
Acta Neurol Scand 2011: 124: 361–367 DOI: 10.1111/j.1600-0404.2010.01484.x
ACTA NEUROLOGICA SCANDINAVICA
Cognitive impairment using education-based cutoff points for CMMSE scores in elderly Chinese people of agricultural and rural Shanghai China Cui G-H, Yao Y-H, Xu R-F, Tang H-D, Jiang G-X, Wang Y, Wang G, Chen S-D, Cheng Q. Cognitive impairment using education-based cutoff points for CMMSE scores in elderly Chinese people of agricultural and rural Shanghai China. Acta Neurol Scand: 2011: 124: 361–367. 2011 John Wiley & Sons A ⁄ S. Objectives – To evaluate cognitive impairment (CI) in rural China using the Chinese version of the Mini-Mental Status Examination (CMMSE) and compare the prevalence of CI using two different cutoff points. Materials & methods – A population-based survey was conducted of 2809 people aged 60 years and above in a community of two towns (Huaxin and Xujing) in the Qingpu district, located in the western suburb of Shanghai. Face-to-face interviews were carried out to collect relevant information with questionnaires. The Chinese version of the Mini-Mental State Examination with either a 23 ⁄ 24 cutoff point or a cutoff point varying according to education level (AEL) was used to screen subjects for CI. Results – Among these subjects, the mean age was 70.6 years (SD = 6.6) and ranged from 60 to 92 years and included 1010 (36.0%) men and 1799 (64.0%) women. The mean age was 70.7 years (SD = 6.4) for men and 70.5 years (SD = 6.7) for women. Of the 2809 subjects, 2010 (71.5%) had no formal education, 607 (21.6%) completed 1–6 years of education, and 173 (6.2%) completed more than 6 years of school education. The prevalence of CI was 35.6% (95% CI: 33.8–37.4) for both genders when the cutoff point of 23 ⁄ 24 was used. However, when the cutoff point was altered with respect to different education levels, the prevalence of CI was 7.0%. For each item of the CMMSE, increased years of education correlated with a higher item score, with the exception of the ÔNamingÕ item score. Conclusions – This study demonstrates that screening of CI using the AEL cutoff scores is feasible in a low-education population. Determining whether the 23 ⁄ 24 cutoff point is suitable for the Chinese people requires future prospective studies in a large Chinese population.
Introduction
Dementia, cognitive impairment (CI), and normal aging represent a continuum of cognitive states encountered in the elderly (1). The assessment of CI plays a major role in the early detection of dementia, and early treatment is useful for slowing patientsÕ deterioration. The Mini-Mental State Examination (MMSE) has been widely used in
G.-H. Cui1,2, Y.-H. Yao1,2, R.-F. Xu3, H.-D. Tang1, G.-X. Jiang2,4, Y. Wang1, G. Wang1, S.-D.Chen1, Q. Cheng1,2 1 Department of Neurology, Ruijin Hospital Affiliated with the School of Medicine, Shanghai Jiao Tong University; 2School of Public Health, Shanghai Jiao Tong University; 3Qingpu District Center for Disease Control and Prevention, Shanghai, China; 4Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden
Key words: Chinese version of the Mini-Mental State Examination; cognitive impairment; cutoff point; prevalence Q. Cheng and S.-D. Chen Department of Neurology, Ruijin Hospital affiliated with the School of Medicine, Shanghai Jiao Tong University, 197 Ruijin No. 2 Road, Shanghai, 200025, China Tel. ⁄ Fax: +86 21 53061167 e-mail:
[email protected] Accepted for publication December 16, 2010
clinical and epidemiological studies as a standardized screen for CI (2). It consists of 30 items of dichotomous questions that test performance in seven cognitive domains including orientation to time (5 points), orientation to place (5 points), registration (3 points), attention and calculation (5 points), recall (3 points), language (8 points), and visual construction (1 point). The cutoff point for the MMSE is 24, with a score of 23 or less 361
Cui et al. indicating the presence of cognitive disturbance. The MMSE has been translated into Chinese [Chinese version of the Mini-Mental Status Examination (CMMSE)], with small modifications based on the sociocultural differences of the Chinese population, and has been utilized as a dementiascreening instrument for epidemiological studies (3, 4). For example, according to regional divisions of China, test items for orientation to place were adapted as to ÔProvince, district, street, place, floorÕ to replace the phrase ÔCountry, town, street, place, floor.Õ An alliteration in Chinese Ôforty-four stone lionsÕ replaced the phrase ÔNo, ifs ands or buts,Õ which has no suitable Chinese counterpart for the repetition phrase. Earlier studies have found that education is strongly associated with MMSE performance (5). In developing countries, illiteracy is still widely prevalent, particularly among the elderly population (6). Therefore, studies in China adapted the cutoff points according to the educational level (AEL) of respondents: 17 ⁄ 18 for those without formal education, 20 ⁄ 21 for those with 1–6 years of education (primary school), and 24 ⁄ 25 for participants with more than 6 years of education (middle school or higher) (3). The sensitivity and specificity of the CMMSE were reported to be 85.2% and 92.7% in a study of dementia in Shanghai (3). The present study was aimed to compare the prevalence of CI with these two different cutoff point strategies in rural China by the MMSE and evaluate the scores of the CMMSE items in this population.
Hospital affiliated with the School of Medicine, Shanghai Jiao Tong University, between August 2005 and April 2008. Interviewers explained the study and obtained written informed consent prior to beginning each interview. Consent was indicated by thumbprint by those participants who were illiterate. For the severely demented, consent was signed by the legal guardian accompanying them to the interview. Subjects
There are eight towns in the Qingpu district, located in the western suburb of Shanghai. With the consideration of feasibility for the study, two towns (Huaxin and Xujing) were selected as the study area. All residents aged 60 years and over with permanent residence in the two towns were eligible for our study. According to the latest local census, the number of people aged ‡60 in 2005 was 3829, and 2867 respondents (74.9%) completed the interview. Reasons for not participating were unwillingness or inability to come to the investigation. Of the 2867 subjects, 58 of those completing the interview did not fulfill the CMMSE because of hearing impairment (23), speech problems (26), diagnosed dementia (2), refusal to cooperate (6), and psychosis (1). Thus, a total of 2809 subjects who had completed the interview and fulfilled the CMMSE were included in the present analysis. Of the 2809 subjects, 1799 were women and 1010 were men, women were over-represented because more men than women were not participating in our study because of different reasons.
Materials and methods Study design
Measurement
A prospective population-based cohort study of two towns in the Qingpu district of a Shanghai suburb was conducted in 2005 as part of a study on common mechanisms between dementia and diabetes. An investigational questionnaire titled ÔThe common mechanism between dementia and diabetes epidemiologic questionnaireÕ was designed, and the main contents included: (i) Socio-demographic data: name, gender, age, nationality, marital status, and occupation; (ii) Previous history of disease: hypertension, AlzheimerÕs disease, diabetes mellitus, and head injury; (iii) Putative associated factors: smoking, drinking, physical activity, and diet; and (iv) Physical examination: weight, height, waist, hip, systolic blood pressure, and diastolic blood pressure. Face-to-face interviews were carried out by teams of trained clinical interviewers from Ruijin
The Chinese version of the MMSE was used to assess the cognitive function of the populations. The CMMSE assessment took about 15–20 min. Interviews were conducted in a private room to minimize distractions and disturbances.
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Cutoff points
We compared two different cutoff points: one of 23 ⁄ 24, which is widely used in Western countries, and one according to the education level of the respondent (AEL): 17 ⁄ 18 for those without formal education, 20 ⁄ 21 for those with 1–6 years of education (primary school), and 24 ⁄ 25 for participants with more than 6 years of education (middle school or higher). Subjects who screened positive by the different cutoff points were categorized as CI CMMSE23 ⁄ 24 or CMMSEAEL.
Education-based cutoff points for CMMSE scores Statistical analysis
Overall and gender-specific prevalences of CI were estimated. A t-test or one-way analysis of variance was used for the comparison of measurement data, and the chi-square test was used for the comparison of categorical data. All statistical analyses were performed with SPSS 13.0 Statistical Software (SPSS Inc., Chicago, IL, USA). Results Preliminary analysis
There were 2809 subjects aged 60 years and over that were included in the study. Among these subjects, the mean age was 70.6 years (SD = 6.6), ranging from 60 to 92 years. The subjects included 1010 (36.0%) men and 1799 (64.0%) women. The mean age was 70.7 years (SD = 6.4) for men and 70.5 years (SD = 6.7) for women. Of the 2809 subjects, 2010 (71.5%) had no formal education, 607 (21.6%) completed 1–6 years of education, and 173 (6.2%) had more than 6 years of school education. The total score of the MMSE ranged from 5 to 30 with a mean of 24.4 and SD of 4.2. There was a significant difference on the CMMSE between men (25.9 3.6) and women (23.5 4.2; P < 0.01). In addition, there were significant group differences of total CMMSE scores based on the subjectsÕ education levels: 23.25 4.10 for those who had no formal education; 26.93 2.81 for those with 1–6 years of education; and 28.31 2.07 for those with more than 6 years of education (P < 0.01). Only 7.3% of subjects (n = 206) answered all questions correctly and earned a total score of 30, whereas 35.6% of subjects (n = 1001) scored 23 or lower. The correct response rate for each item ranged from 26.5% (visual construction) to 99% (naming). Prevalence of CI
The prevalence of CI under the two cutoff points is shown in Table 1. Among the 2809 study subjects, 1001 people (190 men and 811 women) screened positive for CI according to the cutoff point of 23 ⁄ 24. Using this cutoff point, the prevalence of CI was 35.6% (95% CI: 33.8–37.4) for both genders, 18.8% (95% CI: 16.4–21.2) for men and 45.1% (95% CI: 43.0–47.0) for women. When the AEL cutoff point was used to account for differences in education, only 198 people (42 men and 156 women) screened positive. The prevalence of CI in the study population using the AEL criteria was 7.0% (95% CI: 6.1–7.9) for both genders, 4.2% (95% CI: 3.6–4.8) for men and 8.7% (95% CI: 8.0–
Table 1 Prevalence of cognitive impairment by age, sex, and educational level using two cutoff points
CMMSE23 ⁄ 24 Female Male All Education level No formal education Primary school Middle school or higher Age (years) 60–69 70–79 80+ Female 60–69 70–79 80+ Male 60–69 70–79 80+ CMMSEAEL Female Male All Educational level No formal education Primary school Middle school or higher Age (years) 60–69 70–79 80+ Female 60–69 70–79 80+ Male 60–69 70–79 80+
n
Prevalence (95% CI)
P
811 ⁄ 1799 190 ⁄ 1010 1001 ⁄ 2809
45.1 (43.0–47.0) 18.8 (16.4–21.2) 35.6 (33.8–37.4)
