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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 ap-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 inTable 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 andp=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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This study showed that older adults in China had a high level of undetected dementia, especially among females (compared to males), rural residents (compared to urban), age <75 years (compared to other age groups), and illiterate people (compared to literate). The overall proportion of undetected dementia was 85.8%, which was much higher than the world average and some developed countries. Systematic research was conducted until October 2016 for studies reporting the proportion of undetected dementia in either the community or in residential care settings worldwide and found that the pooled rate of undetected dementia was 61.7% (10). Amjad et al. estimated that about 58.7% of older adults with probable dementia were undetected in the US (11). The World Health Organization’s (WHO)Global action plan on the public health response to dementia 2017–2025set out a target for countries: “in at least 50% of countries, as a minimum, 50% of the estimated number of people with dementia are diagnosed by 2025” (12).
This study showed progress in China toward this goal. According to a previous study with a sample of 7,072 participants aged ≥60 years in 6 PLADs during 2007–2011, a peak of 93.1% of dementia patients were undetected (2). An explanation for the recent decline to 85.8% found in this study may be due to general improvements of socioeconomic conditions and health services, such as medical insurance coverage, the establishment of memory clinics, and the increased education level of the public.
This study found that an increased risk of having undetected dementia was strongly associated with low socioeconomic factors such as residing in rural areas, having lower levels of education, and being windowed, which was consistent with previous studies (2,11) and may be due to the lack of healthcare, poor health awareness, and health insurance coverage. This study also found that women had a higher proportion of undetected dementia than men, which is consistent with a previous study in China but was different from the US (11). Gaps still existed in dementia diagnosis in rural and urban areas with 93.5% of patients being undetected in rural areas and 77.5% being undetected in urban. This might be due to rural elderly residents having lower awareness and worse medical conditions when compared to urban residents or due to the higher prevalence of dementia in rural areas than in urban areas (13). This study also found that in urban areas, the proportion of undetected dementia increased with age before 75 years but decreased with age after 75 years. People with dementia before the age of 75 may have mild symptoms, which is considered normal aging, or, because of stigma, they might not want a dementia diagnosis while they can live without help.
Detecting people living with dementia is crucial for necessary care and treatment. Early diagnosis allows for advanced-care planning and improves prognosis (2). However, there are many factors that affected the accurate diagnosis of dementia such as the following: a shortage of dementia specialists; the stigma associated with dementia; inconsistent versions or cutoff scores for neuropsychological tests; the costs of certain advanced techniques to assist with the diagnosis, such as positron emission tomography (PET), which are not fully covered by health insurance; the refusal by patients and their families of invasive diagnostic examinations such as lumbar puncture and brain pathological examinations; lack of regular screening programs in community settings; and an low awareness of dementia (1,14-15).
This study was subject to some limitations. First, the proportion of undetected dementia among community-dwelling older people might be overestimated because patients with dementia living in hospitals or private nursing institutions were not included in this study. Second, the data for undiagnosed dementia for each type cannot be distinguished in this study, because the types of dementia were not subdivided in the diagnostic stage. Furthermore, this study was conducted not for the purpose of identifying the knowledge, attitudes, and practice of screening and early diagnosis of dementia in primary care and cannot offer information for the examination of factors affecting accessibility to diagnosis.
In conclusion, this study represents the most up-to-date data with a relatively large sample size and standard diagnostic criteria to estimate the proportion of undetected dementia (85.8%) in China. Despite improved access to health services, inadequate diagnosis and management for dementia is still common, particularly in rural areas. Efforts should be made to increase the awareness of dementia in the public, to improve the capacity of early recognition of dementia by primary care physicians in community settings, and also to improve the local diagnostic capability of dementia.
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