Epidemiology of Alzheimer's disease and other forms of dementia in China, 1990–2010: a systematic review and analysis
ABSTRACT Background China is increasingly facing the challenge of control of the growing burden of non-communicable diseases. We assessed the epidemiology of Alzheimer's disease and other forms of dementia in China between 1990, and 2010, to improve estimates of the burden of disease, analyse time trends, and inform health policy decisions relevant to China's rapidly ageing population. Methods In our systematic review we searched for reports of Alzheimer's disease or dementia in China, published in Chinese and English between 1990 and 2010. We searched China National Knowledge Infrastructure, Wanfang, and PubMed databases. Two investigators independently assessed case defi nitions of Alzheimer's disease and dementia: we excluded studies that did not use internationally accepted case defi nitions. We also excluded reviews and viewpoints, studies with no numerical estimates, and studies not done in mainland China. We used Poisson regression and UN demographic data to estimate the prevalence (in nine age groups), incidence, and standardised mortality ratio of dementia and its subtypes in China in 1990, 2000, and 2010. Findings Our search returned 12 642 reports, of which 89 met the inclusion criteria (75 assessed prevalence, 13 incidence, and nine mortality). In total, the included studies had 340 247 participants, in which 6357 cases of Alzheimer's disease were recorded. 254 367 people were assessed for other forms of dementia, of whom 3543 had vascular dementia, frontotemporal dementia, or Lewy body dementia. In 1990 the prevalence of all forms of dementia was 1·8% (95% CI 0·0–44·4) at 65–69 years, and 42·1% (0·0–88·9) at age 95–99 years. In 2010 prevalence was 2·6% (0·0–28·2) at age 65–69 years and 60·5% (39·7–81·3) at age 95–99 years. The number of people with dementia in China was 3·68 million (95% CI 2·22–5·14) in 1990, 5·62 million (4·42–6·82) in 2000, and 9·19 million (5·92–12·48) in 2010. In the same period, the number of people with Alzheimer's disease was 1·93 million (1·15–2·71) in 1990, 3·71 million (2·84–4·58) people in 2000, and 5·69 million (3·85–7·53) in 2010. The incidence of dementia was 9·87 cases per 1000 person-years, that of Alzheimer's disease was 6·25 cases per 1000 person-years, that of vascular dementia was 2·42 cases per 1000 person-years, and that of other rare forms of dementia was 0·46 cases per 1000 person-years. We retrieved mortality data for 1032 people with dementia and 20 157 healthy controls, who were followed up for 3–7 years. The median standardised mortality ratio was 1·94:1 (IQR 1·74–2·45). Interpretation Our analysis suggests that previous estimates of dementia burden, based on smaller datasets, might have underestimated the burden of dementia in China. The burden of dementia seems to be increasing faster than is generally assumed by the international health community. Rapid and eff ective government responses are needed to tackle dementia in low-income and middle-income countries.
- SourceAvailable from: Shufeng Zhou[Show abstract] [Hide abstract]
ABSTRACT: There is an increasing prevalence of Alzheimer's disease (AD), which has become a public health issue. However, the underlying mechanisms for the pathogenesis of AD are not fully understood, and the current therapeutic drugs cannot produce acceptable efficacy in AD patients. Previous animal studies have shown that coffee (Coff), caffeine (Caff), and melatonin (Mel) have beneficial effects on AD. Disturbed circadian rhythms are observed in AD, and chronotherapy has shown promising effects on AD. In this study, we examined whether a combination of Coff or Caff plus Mel produced a synergistic/additive effect on amyloid-β (Aβ) generation in Neuro-2a (N2a)/amyloid precursor protein (APP) cells and the possible mechanisms involved. Cells were treated with Coff or Caff, with or without combined Mel, with three different chronological regimens. In regimen 1, cells were treated with Coff or Caff for 12 hours in the day, followed by Mel for 12 hours in the night. For regimen 2, cells were treated with Coff or Caff plus Mel for 24 hours, from 7 am to 7 am the next day. In regimen 3, cells were treated with Coff or Caff plus Mel with regimen 1 or 2 for 5 consecutive days. The extracellular Aβ40/42 and Aβ oligomer levels were determined using enzyme-linked immunosorbent assay (ELISA) kits. The expression and/or phosphorylation levels of glycogen synthase kinase 3β (GSK3β), Erk1/2, PI3K, Akt, Tau, Wnt3α, β-catenin, and Nrf2 were detected by Western blot assay. The results showed that regimen 1 produced an additive antiamyloidogenic effect with significantly reduced extracellular levels of Aβ40/42 and Aβ42 oligomers. Regimen 2 did not result in remarkable effects, and regimen 3 showed a less antiamyloidogenic effect compared to regimen 1. Coff or Caff, plus Mel reduced oxidative stress in N2a/APP cells via the Nrf2 pathway. Coff or Caff, plus Mel inhibited GSK3β, Akt, PI3K p55, and Tau phosphorylation but enhanced PI3K p85 and Erk1/2 phosphorylation in N2a/APP cells. Coff or Caff, plus Mel downregulated Wnt3α expression but upregulated β-catenin. However, Coff or Caff plus Mel did not significantly alter the production of T helper cell (Th)1-related interleukin (IL)-12 and interferon (IFN)-γ and Th2-related IL-4 and IL-10 in N2a/APP cells. The autophagy of cells was not affected by the combinations. Taken together, combination of Caff or Coff, before treatment with Mel elicits an additive antiamyloidogenic effects in N2a/APP cells, probably through inhibition of Aβ oligomerization and modulation of the Akt/GSK3β/Tau signaling pathway.Drug Design, Development and Therapy 01/2015; 9:241-72. · 3.03 Impact Factor
- Journal of the American Geriatrics Society 09/2014; 62(9). · 4.22 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: There is a lack of validated tools for assessing Alzheimer's disease (AD) across Asia. This study evaluates the psychometric properties of the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), Disability Assessment for Dementia (DAD), and Neuropsychological Test Battery (NTB) in Asian participants. Participants with mild to moderate AD (n=251) and healthy controls (n=51) from Mainland China, Taiwan, Singapore, Hong Kong, and South Korea completed selected instruments at several time points. Test-retest reliability was better than 0.70 for all tests. AD participants performed significantly more poorly than controls on every score. Within the AD group, greater disease severity corresponded to significantly poorer performance. The AD group test performance worsened over time and there was a trend for worse performance in AD compared to healthy controls over time. The ADAS-Cog, DAD, and NTB are reliable, valid, and responsive measures in this population and could be used for clinical trials across Asian countries/regions.American journal of neurodegenerative disease. 01/2014; 3(3):158-69.
www.thelancet.com Vol 381 June 8, 2013
Epidemiology of Alzheimer’s disease and other forms
of dementia in China, 1990–2010: a systematic review
Kit Yee Chan, Wei Wang, Jing Jing Wu, Li Liu, Evropi Theodoratou, Josip Car, Lefk os Middleton, Tom C Russ, Ian J Deary, Harry Campbell*,
Wei Wang*, Igor Rudan*; on behalf of the Global Health Epidemiology Reference Group (GHERG)
Background China is increasingly facing the challenge of control of the growing burden of non-communicable
diseases. We assessed the epidemiology of Alzheimer’s disease and other forms of dementia in China between 1990,
and 2010, to improve estimates of the burden of disease, analyse time trends, and inform health policy decisions
relevant to China’s rapidly ageing population.
Methods In our systematic review we searched for reports of Alzheimer’s disease or dementia in China, published in
Chinese and English between 1990 and 2010. We searched China National Knowledge Infrastructure, Wanfang, and
PubMed databases. Two investigators independently assessed case defi nitions of Alzheimer’s disease and dementia:
we excluded studies that did not use internationally accepted case defi nitions. We also excluded reviews and
viewpoints, studies with no numerical estimates, and studies not done in mainland China. We used Poisson
regression and UN demographic data to estimate the prevalence (in nine age groups), incidence, and standardised
mortality ratio of dementia and its subtypes in China in 1990, 2000, and 2010.
Findings Our search returned 12 642 reports, of which 89 met the inclusion criteria (75 assessed prevalence,
13 incidence, and nine mortality). In total, the included studies had 340 247 participants, in which 6357 cases of
Alzheimer’s disease were recorded. 254 367 people were assessed for other forms of dementia, of whom 3543 had
vascular dementia, frontotemporal dementia, or Lewy body dementia. In 1990 the prevalence of all forms of dementia
was 1·8% (95% CI 0·0–44·4) at 65–69 years, and 42·1% (0·0–88·9) at age 95–99 years. In 2010 prevalence was 2·6%
(0·0–28·2) at age 65–69 years and 60·5% (39·7–81·3) at age 95–99 years. The number of people with dementia in
China was 3·68 million (95% CI 2·22–5·14) in 1990, 5·62 million (4·42–6·82) in 2000, and 9·19 million (5·92–12·48)
in 2010. In the same period, the number of people with Alzheimer’s disease was 1·93 million (1·15–2·71) in 1990,
3·71 million (2·84–4·58) people in 2000, and 5·69 million (3·85–7·53) in 2010. The incidence of dementia was
9·87 cases per 1000 person-years, that of Alzheimer’s disease was 6·25 cases per 1000 person-years, that of vascular
dementia was 2·42 cases per 1000 person-years, and that of other rare forms of dementia was 0·46 cases per
1000 person-years. We retrieved mortality data for 1032 people with dementia and 20 157 healthy controls, who were
followed up for 3–7 years. The median standardised mortality ratio was 1·94:1 (IQR 1·74–2·45).
Interpretation Our analysis suggests that previous estimates of dementia burden, based on smaller datasets, might
have underestimated the burden of dementia in China. The burden of dementia seems to be increasing faster than is
generally assumed by the international health community. Rapid and eff ective government responses are needed to
tackle dementia in low-income and middle-income countries.
Funding Nossal Institute of Global Health (University of Melbourne, Australia), the National 12th Five-Year Major Projects
of China, National Health and Medical Research Council Australia–China Exchange Fellowship, Importation and
Development of High-Calibre Talents Project of Beijing Municipal Institutions, and the Bill & Melinda Gates Foundation.
Chronic non-communicable diseases have become the
leading cause of morbidity and mortality in low-income
and middle-income countries.1 Over the next decade,
the burden of non-communicable diseases will grow
rapidly, driven mainly by increased life expectancy in
large low-income and middle-income countries such as
China, India, Brazil, and South Africa.2–6 Unless eff ec-
tive means to prevent and control non-communicable
diseases are implemented, the economic development
of these countries will be hindered.7 Of the many non-
communicable diseases that need attention, dementia
is predicted to have the greatest economic and social
eff ect. The World Alzheimer Report 2010 8 estimated that
ageing of the global population will make the economic
eff ect of dementia greater than that of cancer, heart
disease, and stroke combined. In China, the problem of
dementia might become exacerbated by the one-child
policy and large internal migration, with fewer adults of
working age available to provide continuing care to
the millions of people with dementia, particularly in
Lancet 2013; 381: 2016–23
See Comment page 1967
Nossal Institute for Global
Health, University of Melbourne,
Australia (K Y Chan PhD); Beijing
Municipal Key Laboratory of
Clinical Epidemiology, School of
Public Health, Capital Medical
University, Beijing, China
(W Wang  MPH, J J Wu MPH,
Prof W Wang  PhD); Johns
Hopkins School of Public Health,
Baltimore, MD, USA (L Liu PhD);
Centre for Population Health
Sciences, The University of
Edinburgh Medical School
(E Theodoratou PhD,
Prof H Campbell MD,
Prof I Rudan PhD, K Y Chan),
Centre for Cognitive Ageing and
Department of Psychology
(T C Russ MTCPsych,
Prof I J Deary FRSE), Alzheimer
Scotland Dementia Research
Centre, Department of
Psychology (T C Russ,
Prof I J Deary), The University of
Edinburgh, Edinburgh, UK;
Neuroepidemiology and Ageing
Research Unit, School of Public
Health, Faculty of Medicine,
Imperial College London,
London, UK (J Car PhD,
Prof L Middleton MD); Scottish
Dementia Clinical Research
Network, NHS Scotland,
Edinburgh, UK (T C Russ); and
School of Medical Sciences, Edith
Cowan University, Perth,
Australia (Prof W Wang )
Prof Igor Rudan, Chair in
International Health and
Molecular Medicine, Centre for
Population Health Sciences, The
University of Edinburgh Medical
School, Teviot Place,
Edinburgh EH8 9AG, UK
Prof Wei Wang, Postgraduate
Medicine, School of Medical
Sciences, Edith Cowan University,
Perth, WA 6027, Australia
www.thelancet.com Vol 381 June 8, 2013 2017
Population surveillance data are crucial for the
development of eff ective policies and programmes for
prevention and management of dementia, but such data
are inadequate in most low-income and middle-income
countries.11,12 For this reason, the fi rst estimates of the
worldwide burden of dementia have been based on a
combination of a few reports and expert opinion.13,14
Alzheimer’s Disease International developed the fi rst
data-driven estimate in 2009.15 Their report had reason-
able coverage for only 11 of 21 regions worldwide, it was
restricted to patients aged 60 years or older, and the
estimate for China was low compared with other low-
income and middle-income regions.15,16 Estimation of the
burden in China relied on a review of 25 studies done
between 1980, and 2004, by Chinese investigators.16
Alzheimer’s Disease International complemented these
sources with a search of other publicly available databases
for more recent studies, but acknowledged that their
inability to do a fully systematic review of Chinese work
might be a substantial shortcoming, making their esti-
mates for east Asia provisional at best.15 The 2012 WHO
report17 on dementia adopted the estimates of Alzheimer’s
Disease International, but acknowledged their limitations
and called for further epidemiological studies in low-
income and middle-income countries.
China’s academic databases are a valuable and largely
unexplored resource for understanding the epidemiology
of dementia and many other non-communicable dis-
eases.18–21 We did a systematic review of epidemiological
studies of dementia and its subtypes—particularly
Alzheimer’s disease and vascular demen tia—in both
Chinese and English. We estimated the prevalence,
incidence, and mortality associated with Alzheimer’s
disease, vascular dementia, and other forms of dementia
in China, assessing size and time trends between
1990 and 2010. We also investigated the diff erences in
prevalence by age and sex and between rural and urban
regions, to inform policy and priority setting.
Search strategy and exclusion criteria
We searched China National Knowledge Infrastructure,
Wanfang, and PubMed. Searches were done in parallel
by WW (1) and JJW. The search was limited to studies
published between 1990, and 2010. The appendix shows
the search terms. We excluded duplicates within and
between the databases, studies with no numerical
estimates, studies of Chinese populations done outside
of mainland China, reviews, and viewpoints (appendix).
We excluded studies of animals, studies with no
clear denominator or inappropriate standardised rates,
studies that assessed dementia only, men only, military
personnel only, or were set in nursing homes, and
studies that did not have adequate controls. We also
excluded studies that did not adopt internationally
recognised defi nitions of Alzheimer’s disease and other
dementia (Diagnostic and Statistical Manual of Mental
Disorders or International Classifi cation of Diseases
criteria for dementia, National Institute of Neurological
and Communicative Disorders and Stroke and the
Alzheimer’s Disease and Related Disorders Association
criteria for Alzheimer’s disease, and National Institute
of Neurological Disorders and Stroke and Association
Internationale pour la Recherché et l’Enseignement en
Neurosciences criteria for vascular dementia).22–26
Procedures and statistical analyses
Consistent methods and criteria for each study are crucial
to the accuracy and precision of our estimates.27 Two
researchers with expertise in psychiatry, dementia, and
cognitive ageing (TCR and IJD) independently reviewed
all eligible studies to assess the quality of the case
defi nitions used. They used the following ratings:
3=reported Diagnostic and Statistical Manual of Mental
Disorders or International Classifi cation of Diseases
criteria or a similarly acceptable standard; 2=other criteria,
but less widely accepted; 1=only basic screening for
dementia (eg, Mini Mental State Examination);
0=insuffi cient information or no report of dementia
criteria. We estimated age-specifi c prevalences of demen-
tia in China by Poisson regression (appendix). Prevalence
for each 5-year age group—estimated for 1990, 2000, and
2010—was multiplied by the corresponding 5-year
population subgroups in China, available from the UN’s
Population Division,28 to estimate the total number of
people with dementia, Alzheimer’s disease, vascular
For the China National
Knowledge Infrastructure see
For Wanfang see http://www.
See Online for appendix
Figure 1: Study selection
Four studies provided information on both incidence and prevalence, three on both incidence and mortality, and
one on both prevalence and mortality. *Internet searches and monographs. †Did not provide original, numerical
estimates of prevalence, incidence, or mortality.
12 642 reports identified through
7 records identified from
8477 abstracts screened8302 excluded†
175 full-text articles assessed
13 provided incidence data9 provided mortality data75 provided prevalence data
89 studies included
1 non-human study
15 no clear denominator
2 incorrect standardised rates
18 assessed dementia only
3 assessed men or military
3 nursing home studies
18 duplicate publications
12 inadequate case definitions
14 no adequate controls for
www.thelancet.com Vol 381 June 8, 2013
dementia, and other dementia in those three years. We
then extracted information on age-specifi c prevalence by
sex and rural versus urban population when possible. We
made a database containing: mean age for each age group
reported in the study; number of participants in each age
group; and proportion of participants diagnosed with
Alzheimer’s disease, other forms of dementia (if available),
and any form of dementia.
We estimated incidence from prospective studies
that enrolled healthy cohorts and then assessed the
cohorts for development of Alzheimer’s disease,
vascular dementia, other types of dementia, and all
dementia. We recorded the number of new cases in
people aged 60 years or older at the beginning of the
study, to make the estimates com parable. We then
added the number of new cases and person-years across
studies and expressed the incidence as the number of
new cases per 1000 person-years. We also estimated the
increase in mortality of patients with dementia com-
pared with healthy controls. We adjusted mortality rate
ratios in the studies for the baseline diff erence in
expected mortality and estimated standardised mortality
ratio. The appendix provides further details of modelling
and statistical analyses.
Sample size (n)
Main case defi nition*
Additional diagnostic tests used to establish case defi nition*
Mini-Mental State Examination
Hachinski Ischemic Score
Activities of daily living
Health status or disease history
Physical examination (height, weight, blood pressure,
(Continues in next column)
(Continued from previous column)
Fuld Object Memory Evaluation
Pfeiff er Function Activity questionnaire
Wechsler Adult Intelligence Scale digit span
Basic demographic information
Wechsler Adult Intelligence Scale block design
Rapid Vocabulary Retrieve
Hamilton Depression Rating Scale
CT or MRI
Hastgawa Dementia Scale
Clinical Dementia Rating Scale
Verbal Fluency Test
Center for Epidemiologic Studies Depression Scale
Key informant survey (for those who are alive but have
severe dementia, are deaf, have symptoms, or whose
health status prevents interview)
Crichton Royal Behavioural Scale
Key informant survey (for those who died)
Global Deterioration Scale
Clock Drawing Test
Wechsler Adult Intelligence Scale
Multidisciplinary team of psychiatrists, neurologists, and
other medical specialties, with or without trained fi eld staff
Psychiatrists with trained fi eld staff
Neurologists with trained fi eld staff
Not specifi ed
We included 75 cross-sectional studies. CCMD=Chinese classifi cation of mental
disorders. ICD=International classifi cation of diseases. NINDS-AIREN=National
Institute of Neurological and Communicative Disorders and Stroke and
Association Internationale pour la Recherche et I’Enseignement en Neurosciences.
NINCDS-ADRDA=National Institute of Neurological and Communicative
Disorders and Stroke and the Alzheimer’s Disease and Related Disorders
Association. DSM=Diagnostic and Statistical Manual of Mental Disorders. *Several
tests were typically used in each study. The tests listed here were used in at least
fi ve studies, the appendix shows a full list of tests used in each study.
Table 1: Characteristics of the cross-sectional studies
www.thelancet.com Vol 381 June 8, 2013 2019
Role of the funding source
The sponsor of the study had no role in study design,
data collection, data analysis, data interpretation, or
writing of the report. The corresponding author had full
access to all the data in the study and had fi nal
responsibility for the decision to submit for publication.
Our initial screen returned 8490 results from
China National Knowledge Infrastructure, 4142 from
Wanfang, and ten from PubMed. 89 studies met all the
inclusion criteria (fi gure 1). The appendix shows a full
list of studies included, table 1 shows details of the
75 cross-sectional studies. The cross-sectional studies
were mainly large, published in the past decade, and
were led by multi disciplinary teams of specialists. They
included patients from nearly all of the mainland
Chinese provinces, with the exception of two sparsely
populated provinces and three autonomous regions
(appendix). The appendix lists all the diagnostic tests
and criteria used in each study and we discuss diff erent
case defi nitions of dementia.22–26 The appendix also
shows interobserver agreement,
32 studies (median κ 0·88, IQR 0·82–0·92).
Most studies (75 of 89; 84%) provided estimates of
the prevalence of Alzheimer’s disease and dementia
(fi gure 2), rather than of incidence or mortality, probably
because cross-sectional studies are much cheaper and
easier to do than are longitudinal studies. 340 247 par-
ticipants were included in our analysis representing
6357 cases of Alzheimer’s disease. 254 367 partici pants
were included in our analysis of dementia, includ ing
Figure 2: Prevalence of Alzheimer’s disease and any dementia in 75 studies
The size of each bubble is proportional to sample size. Data are presented for Alzheimer’s disease in 1990 (A), 2000 (B), and 2010 (C), and for any dementia in 1990 (D),
2000 (E), and 2010 (F).
0 50556065 7075 8085 90 95100
Mean age (years)
050 5560657075 808590 95100
Mean age (years)
www.thelancet.com Vol 381 June 8, 2013
3543 cases of vascular dementia, frontotemporal demen-
tia, or Lewy body dementia. The appendix shows the
proportion of dementias that were Alzheimer’s disease
within each 5-year age group.
Table 2 shows the age-specifi c prevalence of Alz-
heimer’s disease and dementia in 1990, 2000, and 2010.
In 1990, the prevalence of Alzheimer’s disease ranged
from 0·1% in people aged 55–59 years to 28·8% for those
aged 95–99 years. The prevalence of all forms of dementia
in 1990 ranged from 0·5% in people aged 55–59 years to
42·1% in people aged 95–99 years. In 2010, the prevalence
of Alzheimer’s disease was 0·2% (95% CI 0·0–72·3) in
people aged 55–59 years and 48·2% (19·0–77·4) for those
aged 95–99 years, with the prevalence of all forms of
dementia ranging between 0·7% (0·0–54·5) and 60·5%
(39·7–81·3; table 2).
The number of people with some form of dementia in
China was 3·68 million (95% CI 2·22–5·14) in 1990,
5·62 million (4·42–6·82) in 2000, and 9·19 million
(5·92–12·48) in 2010. The number of people with
Alzheimer’s disease was 1·93 million (1·15–2·71) in
1990, 3·71 million (2·84–4·58) people in 2000, and 5·69
million (3·85–7·53) in 2010. Throughout this period,
the proportion of Alzheimer’s disease in all forms of
dementia did not change substantially (fi gure 3). In
people aged 55–59 years, roughly a third of patients
with dementia met the criteria for Alzheimer’s disease
compared with four fi fths of patients aged 95–99 years
(appendix). Most cases of dementia in China in all three
periods were in people aged 70–84 years (fi gure 3).
47 of the 75 prevalence studies reported the prevalence
of dementia attributable to vascular dementia and other
forms of dementia (eg, frontotemporal dementia, Lewy
body dementia). The median proportion of vascular
dementia in all forms of dementia was 24·2%
(IQR 17·4–32·7). Rare forms of dementia (excluding
Alz heimer’s disease and vascular dementia) constituted
7·5% (IQR 2·7–10·7) of all dementias, which accords
with our estimates of incidence estimates and previously
Adjusted forStudies included in
anaylsis (n; participants)
Prevalence ratiop value
Women vs men
Age, period of
study, urban or
Age, period of
32 (123 024 participants) 2·37 (95% CI 1·90–2·96)<0·0001
Urban dwellers vs rural
32 (123 024 participants) 1·34 (95% CI 0·93–1·94)0·1150
Women vs men
Age, period of
study, urban or
Age, period of
23 (79 080 participants)1·65 (95% CI 1·51–1·81)<0·0001
Urban dwellers vs rural
23 (79 080 participants)1·54 (95% CI 0·85–2·78)0·1510
Table 3: The eff ects of sex and urban or rural environment on the prevalence of Alzheimer’s disease and
dementia in China
1990 2000 2010
Alzheimer’s diseaseDementia Alzheimer’s disease DementiaAlzheimer’s diseaseDementia
Data are prevalence (95% CI).
Table 2: Estimates of the age-specifi c prevalence of Alzheimer’s disease and all forms of dementia in China in 1990, 2000, and 2010
Figure 3: Predicted numbers of people with any form of dementia and Alzheimer’s disease in China by year
and age group
1 000 000
2 000 000
3 000 000
4 000 000
5 000 000
6 000 000
7 000 000
8 000 000
9 000 000
10 000 000
People with disease (n)
www.thelancet.com Vol 381 June 8, 2013 2021
We investigated whether age-specifi c prevalence was
higher in women than in men, and in rural regions than
in urban regions (table 3). The prevalence of dementia
controlled for age is higher for women than for men but
did not diff er signifi cantly between urban residents and
rural residents (table 3, appendix). The same patterns
hold for Alzheimer’s disease (table 3, appendix).
We used data from 13 prospective studies to estimate
incidence. The number of person-years of follow-up
diff ered between studies of Alzheimer’s disease, vascular
dementia, other dementia, and all dementia (appendix). A
mean of 30 770 people, aged 60 years or older, were
assessed for all four diseases. They were followed up for
an average of 71 518 person-years. Based on 32 116 people
from these prospective studies, the incidence of dementia
in people aged 60 years or older (90 840 person-years of
follow-up), was 9·87 cases per 1000 person-years. The
incidence of Alzheimer’s disease was 6·25 cases per
1000 person-years, for vascular dementia it was 2·42 cases
per 1000 person-years, and for rare forms of dementia
(eg, frontotemporal dementia, Lewy body dementia) it
was 0·46 cases per 1000 person-years (appendix). These
incidences accord with previous reports.13,17,22,29
Nine studies provided information on mortality rate
ratios between patients with dementia and unaff ected
people. 1032 people with dementia and 20 157 healthy
controls were followed up for 3–7 years. Median mortality
was 132 deaths per 1000 person-years (IQR 130–190) in
patients with dementia and 38 deaths per 1000 person-
years in healthy controls. The median mortality rate ratio
was 4·6 (IQR 2·42–5·71), but no adjustment was made
for the diff erence in the mean age; healthy controls were
likely to be older and have higher expected baseline
mortality than participants with dementia. The median
standardised mortality ratio was 1·94 (IQR 1·74–2·45),
which is similar to an estimate of 2·77 by Prince
This study is, to our knowledge, the fi rst large-scale
systematic analysis of the epidemiology of Alzheimer’s
disease and other forms of dementia in a low-income or
middle-income setting. It aims to address a major gap in
policy-relevant health information and sets an example
for further similar analyses.30 The information available
in the Chinese scientifi c literature was suffi cient to
generate reasonably precise estimates of the prevalence
and incidence of Alzheimer’s disease and other forms of
dementia in China over the past two decades. The
prevalence of Alzheimer’s and dementia increased
substantially between 1990 and 2010. The prevalences
also diff er signifi cantly by sex. These fi ndings have
important policy implications because women in China
have a considerably longer life expectancy than do men
and constitute up to 75% of the population of people
aged 85 years and older.28 Furthermore, migration of
young adults from rural to urban regions within China
will result in large numbers of elderly people, especially
women, in rural regions living alone. Those who develop
any form of dementia will be at an increased risk of
becoming vulnerable and isolated, requiring community
support and being dependent on government-supported
programmes of care.
China had more cases of Alzheimer’s disease in
2010 than any other country in the world.15 Our data
suggest that the most recent Alzheimer’s Disease
International estimates15 for China and east Asia, which
relied on an earlier review16 of the Chinese scientifi c
literature and were adopted by WHO,17 might
underestimate the true burden of disease in China by
double. Our study alone suggests that global estimates of
Alzheimer’s disease might need to be revised upwards by
at least 5 million cases, or almost 20%. For a direct
comparison with the World Alzheimer Report, in which all
estimates apply only to people aged 60 years or older, the
cases in patients younger than 60 years in our study
should be removed, reducing this diff erence slightly.
Nevertheless, the absolute numbers of 5·69 million cases
of Alzheimer’s disease and 9·19 million cases of any
dementia in China in 2010 might pose the single largest
challenge to health and social care systems in terms of
fi nding appropriate and aff ordable responses. Future
research in China should give more attention to
quantifying the burden of disease in specifi c ethnic and
cultural groups and exploring reasons for, and con-
sidering the policy implications of, any diff erences.
Although we have aimed to provide the best possible
estimate of the prevalence of dementia in China, our
study has some important limitations. First, although we
selected studies of suffi cient quality done in nearly all
provinces in China, our sample is small for a country of
1·4 billion people. Thus, the overall data on dementia in
China are still insuffi cient: many studies did not provide
prevalence data disaggregated by sex, urban or rural
residence, and subtype of dementia. Second, no studies
have been done in the less developed provinces and
autonomous regions of western China (Gansu, Qinghai,
Inner Mongolia, Tibet, and Ningxia), although these
regions are relatively sparsely populated compared with
the rest of China (appendix). Methods did not vary much
between studies; most studies were either cross-sectional
or had a cross-sectional follow-up within a cohort study.
All incidences and mortalities were calculated with a
cohort study design and used person-years of follow-up,
enabling direct comparison. All included studies were
community-based, to avoid the many biases present in
facility-based studies or in other studies relevant only to
specifi c population subgroups. Nevertheless, the validity
of the data is heavily reliant on the sensitivity and
specifi city of the screening methods and diagnostic
criteria, and standardisation of these methods is im-
portant to reduce observational bias.
Diagnoses of dementia, Alzheimer’s disease, and
vascular dementia were based on internationally accepted
www.thelancet.com Vol 381 June 8, 2013
defi nitions and were similar across studies. The large
overlap in case defi nitions between studies suggests that
the data are generally comparable. Between 1990, and
2010, no major revisions of the diagnostic criteria of
Alzheimer’s disease and dementia occurred that would
invalidate the analysis of time trends (appendix),
although we cannot exclude the possibility that recent
studies have used more rigorous methods and quality
control. Awareness of the disease has increased, which
might have increased diagnosis of milder and earlier
cases compared with 20 years ago. The eff ects of several
other possible biases, such as publication bias, sex-
specifi c diff erences in survival in China, the possible
eff ect of inadequately applied multiphase designs,
misclassifi cation bias, and time lag between study and
publication are discussed further in the appendix.31–34
Our data suggest that the prevalence of dementia in
low-income and middle-income countries is higher than
that previously estimated.31,35,36 Traditionally, research and
media attention in China have often focused on diseases
with higher case-fatality rates—eg, cardio vascular
diseases and cancer. The general lack of awareness of
dementia has important consequences; people do not
seek medical help as frequently as do patients in high-
income countries, and little training is given for the
recognition and management of dementia at all levels of
the health service.37 These factors create a multifaceted
burden on the individual, their family, and society, which
has personal, emotional, fi nancial, and social aspects.8
Because of the substantial care needed by people with
dementia, family and friends become an important
support network, but the reliability and universality of
family care systems in low-income and middle-income
countries are often overestimated.37 With a growing
middle class, this situation is likely to change as family
structures become more like those in high-income
countries and family support becomes less available.38,39
However, a response purely from strained health services
is unlikely to be suffi cient, and wider societal action and
innovative solutions will be needed.
Policy makers in China and other low-income and
middle-income countries face several additional chal-
lenges. Mental and neurological disorders are generally
low priorities in such countries, but our analysis shows
that dementia prevalence in China already matches that
of high-income countries, and will continue to accelerate.
Adequate resources should be provided at the national,
local, family, and individual levels to tackle this rapidly
growing problem, including specialised care to ensure
timely and appropriate prevention, diagnosis, and treat-
ment.40,41 Public awareness campaigns should be used to
counteract common misconceptions about dementia—
eg, that it is not very common in the Chinese population,
that it is a normal part of ageing, or that it is better not to
know about it because nothing can be done to help.30
Peoples’ cultures and beliefs should be considered when
developing campaigns to raise awareness. Healthcare
workers should be well trained in management of
dementia, with the ability to assess, diagnose, treat or
refer, and educate patients and their caregivers.42,43
Moreover, concern is growing that governmental homes
for the elderly have an unfair advantage over non-
governmental homes, which might hinder the develop-
ment of an elderly home industry in a free-market system
and generate a widening gap between wealthy and poor
elderly people in their access to care.44 A key policy
priority should therefore be to plan for the long-term care
of people with dementia and assess models of delivery of
community-based care.45 Additionally, more research
should be done to improve understanding of the diff erent
social and environmental risk factors for dementia.46–48
KYC had the idea for the study, supervised the literature review,
constructed the database, wrote the report, and oversaw the design,
writing, and revision of the report. WW (1) and JJW reviewed the
published work and wrote the report. LL and ET analysed data and
revised the report. JC helped to construct the database and wrote the
report. LM designed the study, interpreted data, and reviewed the report.
TCR and IJD analysed data and wrote the report. HC, WW (2), and IR
oversaw the study design and analysis. HC and WW (2) wrote and
revised the report. IR wrote and revised the report.
Confl icts of interest
We declare that we have no confl icts of interest.
This study was supported by research grants from the Nossal Institute of
Global Health (University of Melbourne, Australia) and the National 12th
Five-Year Major Projects of China (grant number 2012BAI37B03). KYC
was supported by an National Health and Medical Research Council
Australia–China Exchange Fellowship. WW (2) was supported by the
Importation and Development of High-Calibre Talents Project of Beijing
Municipal Institutions. HC and IR were supported by a grant from
Bill & Melinda Gates Foundation.
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