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Dementia is a leading cause of disability in people older than 65 years old worldwide, and dementia patients in China account for approximately 25% of all patients with dementia worldwide (1). According to a previous study, 93.1% of dementia was undetected (2). In order to understand the latest proportion of undetected dementia in China, data from the Prevention and Intervention on Neurodegenerative Disease for Elderly in China (PINDEC) study was analyzed, and the proportion of undetected dementia was estimated using questionnaire-based interviews and a standard procedure of dementia screening and diagnosis. The differences of undetected dementia between demographic and geographic subgroups were analyzed via chi-squared test. This study reported that the proportion of undetected dementia declined from the past but remained at a high level among the elderly in China, especially among those whom were female (compared to male), resided in rural areas (compared to urban), were aged <75 years (compared to other age groups), and were illiterate (compared to literate). Awareness of dementia should be increased in the general public to improve the capacity of early recognition of dementia by primary medical doctors in the community setting and also to improve the local diagnostic capability of dementia.
Dementia is a chronic disease with progressive deterioration in activities of daily living (ADLs), cognition, and behavior leading to severe disability and ultimately death (3). Globally, dementia is one of the most prevalent neurological disorders and accounts for the fourth largest loss of disability-adjusted life years (DALYs) and the second largest proportion of deaths among all neurological disorders (4). A recent meta-analysis reported an overall prevalence of dementia of 5.30% for the Chinese population aged 60 years and above in 2018 (5); this would be an estimated 10 million elderly people affected by dementia in 2019 based on the number of elderly people in China. In recent years, measures including policy initiatives, health education, and training programs were conducted to improve dementia screening and diagnosis, but little is known about the latest proportion of undetected dementia, especially differences between residents of urban and rural areas.
All patients were from the PINDEC study that was initiated in 2015 aiming to understand the epidemiology of neurodegenerative diseases and associated risk factors among the population aged 60 years and above in China. We used multistage clustered sampling to select the study sample based on geographic location, population size, and level of economic development. The selected provincial-level administrative divisions (PLADs) included Beijing, Shanghai, Hubei, Sichuan, Guangxi, and Yunnan. Within each PLAD, one urban district and one rural county were randomly selected as study sites (counties/districts). Within each site, one subdistrict in urban areas and one township in rural areas were selected with probability proportional to size. Within each subdistrict or township, four to eight neighborhood communities or administrative villages were selected with probability proportional to size. Within each neighborhood community or administrative village, 100 to 200 households with people aged 60 years and above were randomly selected as study households. In the final stage, all family members aged 60 years and above who have a registered Hukou (household registration) and lived in the household for more than one year were selected as study participants. A total of 26,164 people were selected and 24,117 participated in the survey. In 2015–2016, 24,117 community residents participated in questionnaire-based interviews and a procedure of dementia screening and diagnosis. The study was approved by the Ethical Committee of the National Center for Chronic and Non-Communicable Disease Control and Prevention, China CDC. All participants provided written informed consent.
Dementia was assessed using a three-stage approach. All participants were first screened with a Chinese version of the Ascertain Dementia 8 (AD8) (6). Participants with AD8 score ≥2 were then assessed with the Mini-Mental State Examination (MMSE) and cognitive impairment was defined as MMSE ≤17 for illiterate participants, ≤20 for those with primary school education and below, and ≤24 for those with junior high school education and above (7–8). In the final stage, all participants with cognitive impairment underwent a thorough clinical examination by neurologists. Dementia was diagnosed based on the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (9).
Descriptive statistical analyses of different undetected dementia were performed for gender, age, and area type (urban/rural) by using software SAS (version 9.4; SAS Institute, Inc. Cary, NC, USA). Chi-squared tests were adopted to analyze the differences of undetected dementia between subgroups, with a p-value of <0.05 considered statistically significant. Patients with undetected dementia were defined as those who were diagnosed in the survey but did not have doctor-diagnosed dementia before.
The characteristics of study participants were presented in Table 1. Among the 24,117 participants in the survey aged 60 years and above, 44.5% were men, 53.7% resided in urban areas, 22.8% were widowed, and 11.7% were living alone. Among 24,117 participants, we diagnosed 740 (3.1%) as having dementia. Among those detected, there were 105 (14.2%) patients who had doctor-diagnosed dementia before. The overall proportion of undetected dementia was 85.8% (95% CI: 83.3%–88.3%), 75.0% (95% CI: 69.2%–80.8%) in men, and 90.4% (95% CI: 87.8%–92.9%) in women. The proportion of undetected dementia was higher in the group aged 70–74 years than the other age groups, higher in widowed participants than non-widowed, higher in people living alone than living with families (Table 2).
Characteristics Number of participants (n=24,117) Proportion
(%)Location Urban 12,950 53.7 Rural 11,167 46.3 Sex Men 10,722 44.5 Women 13,395 55.5 Age group (years old) 60–64 5,346 22.2 65–69 7,033 29.2 70–74 5,076 21.0 75–79 3,639 15.1 ≥80 3,023 12.5 Marital status Non-widowed 18,613 77.2 Widowed 5,504 22.8 Education Illiterate 9,376 38.9 Primary school 7,652 31.7 Junior high school and above 7,089 29.4 Living status Alone 2,824 11.7 With family 21,293 88.3 Abbreviation: n=number. Table 1. General characteristics of the study sample from the Prevention and Intervention on Neurodegenerative Disease for Elderly in China (PINDEC) conducted in 6 provincial-level administrative divisions, 2015–2016.
Characteristics n (%) Overall Urban Rural Number Proportion (%)
(95% CI)p-value Number Proportion (%)
(95% CI)p-value Number Proportion (%)
(95% CI)p-value Sex <0.001 0.004 <0.001 Men 220(29.7) 165 75.0(69.2−80.8) 93 69.4(61.5−77.3) 72 83.7(75.8−91.7) Women 520(70.3) 470 90.4(87.8−92.9) 183 82.4(77.4−87.5) 287 96.3(94.2−98.5) Age group
(years old)0.030 0.011 0.332 60–64 73(9.9) 61 83.6(74.9−92.3) 22 78.6(62.4−94.8) 39 86.7(76.3−97.0) 65–69 129(17.4) 115 89.1(83.7−94.6) 56 84.8(76−93.7) 59 93.7(87.5−99.8) 70–74 130(17.6) 122 93.8(89.7−98.0) 53 91.4(83.9−98.8) 69 95.8(91.1−100.6) 75–79 188(25.4) 158 84.0(78.8−89.3) 66 71.7(62.4−81.1) 92 95.8(91.8−99.9) ≥80 220(29.7) 179 81.4(76.2−86.5) 79 70.5(62.0−79.1) 100 92.6(87.6−97.6) Marital status <0.001 <0.001 0.068 Non-widowed 485(65.5) 393 81.0(77.5−84.5) 187 71.9(66.4−77.4) 206 91.6(87.9−95.2) Widowed 255(34.5) 242 94.9(92.2−97.6) 89 92.7(87.4−98.0) 153 96.2(93.2−99.2) Education <0.001 <0.001 0.001 Illiterate 454(61.4) 430 94.7(92.6−96.8) 138 92.0(87.6−96.4) 292 96.1(93.9−98.3) Primary school 157(21.2) 115 73.2(66.2−80.2) 66 68.0(58.6−77.5) 49 81.7(71.6−91.7) Junior high school and above 129(17.4) 90 69.8(61.7−77.8) 72 66.1(57.0−75.1) 18 90.0(75.6−104.4) Living status 0.043 0.116 0.815 Alone 129(17.4) 118 91.5(86.6−96.4) 39 86.7(76.3−97.0) 79 94.0(88.9−99.2) With family 611(82.6) 517 84.6(81.7−87.5) 237 76.2(71.4−81.0) 280 93.3(90.5−96.2) Overall 740(100.0) 635 85.8(83.3−88.3) 276 77.5(73.2−81.9) 359 93.5(91.0−96.0) Abbreviation: CI=confidence interval. Table 2. Numbers and proportions of undetected dementia by basic characteristics among the elderly (aged ≥60 years) from the Prevention and Intervention on Neurodegenerative Disease for the Elderly in China (PINDEC) conducted in 6 provincial-level administrative divisions, 2015–2016.
The proportion of undetected dementia in rural populations was significantly higher than that in urban populations (93.5% vs. 77.5%, p<0.001). In urban areas, the proportion of undetected dementia increased with age before 75 years but decreased with age after 75 years (p=0.011) and was higher in widowed participants than non-widowed (p<0.001). However, no age group and marital status differences were found among rural residents (p=0.332 and p=0.068, respectively). In addition, both in rural and urban areas, the proportion of undetected dementia was higher in illiterate groups than literate groups. (Table 2).
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