Surveillance of stroke: a global perspective.
ABSTRACT For preventive strategies to be efficient, it is essential to have information on the pattern of disease and exposure to major risk factors that predict future diseases in the population. Basic epidemiological data such as mortality rates are reported for less than one-third of the world's population and are almost exclusively from developed countries. However, it is the developing countries, particularly those in rapid economic and demographic transition, which will experience a major rise in ageing-related diseases. The World Health Organization is intensifying the development and implementation of simple, sustainable surveillance systems that can be used in many different settings around the world. Unlike heart disease and cancer, stroke is a clinically defined disease, which makes it possible to identify trends in different countries irrespective of access to technological equipment. A stepwise approach to increasing detail in the data to be collected for surveillance of stroke is suggested. This will allow countries with different levels of resources and capacity in their health systems to collect useful information for policy.
- SourceAvailable from: PubMed Central[show abstract] [hide abstract]
ABSTRACT: Background. Stroke is an important cause of morbidity and mortality in young adults especially in developing countries. This two-centre prospective study aimed at reviewing the pattern, types, and case fatality of stroke in the young adults in Northwestern part of Nigeria. Methods. Consecutive patients aged 18-40 years admitted to the medical wards of two tertiary hospitals from June 2008 to August 2010 were recruited. Relevant clinical data were obtained from the patients.The survivors were followed up in neurology clinics for 6 months. Results. A total of 71 patients aged 18-40 yrs, (mean age was 31.9 ± 6) comprising 52(73%) males and 19(23%) females were enrolled. Forty two (59.1%) patients had infarctive stroke. The risk factors included hypertension (74.7%) patients, smoking (50.7%), hypercholesterolemia (9.9%), non-hypertensive cardiac diseases (8.5%), HIV (8.5%), diabetes mellitus (4.2%) cocaine and amphetamine (2.8%), and sickle cell disease (2.8%). Only twelve (17%) patients presented within the first 6 hours of onset of stroke. Seventeen (23.9 %) patients died, case fatality in the first 24 and 72 hrs was 4.2% and 19.7%, respectively. Conclusion. Our data suggests that stroke in young adults is not as uncommon as previously suggested. Hypertension, smoking, hypercholesterolemia, cardiac diseases and HIV are the most common risk factors.ISRN neurology. 01/2012; 2012:468706.
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ABSTRACT: Despite increasing burden of stroke in developing countries, population-based data are rare. Through the Trivandrum Stroke Registry, we intend to assess incidence, types, risk factors, and outcome of stroke among urban and rural dwellers of a South Indian community. We ascertained all first-ever strokes occurring among 741,000 urban and 185,000 rural inhabitants of Trivandrum, Kerala. In addition to Steps 1 and 2 of World Health Organization STEPS Stroke Manual, we used multiple supplementary methods to maximize ascertainment of nonfatal and nonhospitalized fatal stroke events in the community. During a 6-month period, 541 strokes were registered, 431 in the urban and 110 in the rural communities. Stroke occurred at a median age of 67 years; only 3.8% of patients were aged <or=40 years. Adjusted annual incidence rates per 100,000 were 135 (95% confidence interval 123 to 146) for total, 135 (122-148) for urban, and 138 (112-164) for rural populations, and 74.8 (66.3 to 83.2), 10.1 (7.0 to 13.2), and 4.2 (2.2 to 6.1) for ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage, respectively. There was more stroke of undetermined type in the rural community. One or more modifiable risk factors were identified in 90% patients. More rural male patients smoked tobacco. The 28th day case fatality rate was 24.5% for urban and 37.1% for rural populations (P=0.011). There are more similarities than differences between developing and developed countries in the epidemiology of stroke. Compared to urban stroke patients, rural ones are less likely to be optimally investigated and treated.Stroke 03/2009; 40(4):1212-8. · 6.16 Impact Factor
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ABSTRACT: Stroke in young adults is more common in India and Sri Lanka and the reasons for this are not well understood. The current study was conducted to elucidate the risk factors and radiologic features in young people (age < 45 years) with ischemic stroke. Sociodemographic data, stroke risk factor information, and laboratory investigations were recorded in 41 cases with first-ever ischemic stroke. Most common risk factors for stroke in the 15- to 45-year-old age group were: hypertension, 8 (21%); family history of stroke, 7 (18%); transient ischemic attack, 6 (16%); hyperlipidemia, 3 (8.0%); and diabetes, two (5%). Age group younger than 15 years included 3 girls and one had a mass attached to the posterior mitral valve leaflet. Our observations underscore the importance of the presence of hypertension, family history of stroke, and transient ischemic attack in young adults and thus to adopt preventative strategies.Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 01/2009; 18(4):304-8.
International Journal of Epidemiology 2001;30:S11–S16
In 1999 stroke was the cause of death in 5.54 million people
worldwide, approximately 10% of all deaths.1Two-thirds of
these deaths occurred in people living in developing countries.2
In addition to it being the third leading cause of death, many
survivors of stroke have to adjust to a life with varying degrees
of disability. The Global Burden of Disease Study3,4described
a measure that integrates the sum of life-years lost due to pre-
mature mortality and years lived with disability adjusted for
severity, the so-called disability-adjusted life years (DALY). In
1999 cerebrovascular disease accounted for 50 million DALY
worldwide, representing 3.5% of all DALY.1Projections to year
2020 show that 61 million DALY are likely to be lost due to
cerebrovascular disease each year, and of these 52 million
(84%) will be in the developing countries.5
Life expectancy is increasing in most parts of the world,
largely because of lower childhood mortality as a result of better
control of previously lethal infectious diseases, but also because
of a decline in mortality in adults. This trend will have a major
impact on the demographic structure of populations in the near
future. The global population aged over 65 years is increasing by
9 million a year. By 2025 there will be more than 800 million
people over 65 years of age in the world;2two-thirds of them
will be living in developing countries. In China alone, there will
be more than 180 million people over the age of 65.6Increases
of up to 300% in the older population are expected in many
developing countries within the next 30 years, especially
in Latin America and Asia. With increasing age, the burden of
non-communicable diseases such as heart disease, stroke and
cancer increases. One of the biggest public health challenges for
many nations will be to prevent and postpone morbidity and
disability due to chronic diseases and to maintain the health,
independence and mobility of an ageing population.
While definitive diagnoses of heart disease and cancers rely
on access to laboratories and trained specialists, stroke is a clin-
ically defined disease, which makes it possible to identify trends
in different countries irrespective of access to technological
equipment. The World Health Organization (WHO) standard
definition of stroke is ‘a focal (or at times global) neurological
impairment of sudden onset, and lasting more than 24 hours
(or leading to death) and of presumed vascular origin’.7The
definition has been proved to be valid in many different settings
and, despite increased use of neuro-imaging, the clinical diag-
nosis remains the foundation of epidemiological studies of stroke.
Along with many chronic diseases stroke can be prevented.
For preventive strategies to be planned and evaluated, it is
essential to have information on the pattern of disease and
exposure to risk factors in the population. Basic epidemiological
data such as mortality rates are reported for approximately 30%
of the world’s population, almost exclusively from developed
countries. However, it is the developing countries, especially
those in rapid demographic transition, which will experience a
major rise in the burden of diseases of an ageing population.
The WHO is recommending simple sustainable surveillance
systems that can be used in sentinel surveillance sites in many
different settings around the world to improve health planning
and to measure the impact of preventive programmes. A step-
wise approach with increasing demands related to the amount
and detail of data is suggested in order that countries with
different levels of resources and sophistication in their health
systems can contribute with data on stroke and its risk factors.
© International Epidemiological Association 2001Printed in Great Britain
Surveillance of stroke: a global perspective
Thomas Truelsen, Ruth Bonita and Konrad J amrozik
For preventive strategies to be efficient, it is essential to have information on the
pattern of disease and exposure to major risk factors that predict future diseases
in the population. Basic epidemiological data such as mortality rates are reported
for less than one-third of the world’s population and are almost exclusively from
developed countries. However, it is the developing countries, particularly those
in rapid economic and demographic transition, which will experience a major
rise in ageing-related diseases.
The World Health Organization is intensifying the development and imple-
mentation of simple, sustainable surveillance systems that can be used in many
different settings around the world. Unlike heart disease and cancer, stroke is a
clinically defined disease, which makes it possible to identify trends in different
countries irrespective of access to technological equipment. A stepwise approach
to increasing detail in the data to be collected for surveillance of stroke is suggested.
This will allow countries with different levels of resources and capacity in their
health systems to collect useful information for policy.
14 March 2001 Accepted
Correspondence: Thomas Truelsen, World Health Organization, Cross-cluster
Surveillance, Noncommunicable Diseases and Mental Health, 20 Avenue
Appia, CH-1211 Geneva 27, Switzerland. E-mail: firstname.lastname@example.org
Surveillance, the ongoing systematic collection, analysis, inter-
pretation and dissemination of health information, is essential
in measuring the impact of efforts to prevent stroke. At the 21st
World Health Assembly in 1968, the WHO held technical dis-
cussions on the national and global surveillance of communicable
disease and identified three main features of surveillance: the
systematic collection of pertinent data; the orderly consolidation
and evaluation of these data; and the prompt dissemination of
the results to those who need to know, particularly those who
are in a position to take action.8Subsequently, the applications
of surveillance concepts have broadened to include a wider range
of health data—risk factors, disability, and health practices—as
well as diseases.9
The primary purpose of establishing and maintaining a system
of surveillance is to provide health workers and policy makers
with a reliable tool to plan cost-effective strategies to meet the
demands for health care and prevention in the population.
Surveillance should be focused on diseases that are or are
likely to become public health problems.10Also, surveillance
programmes are more likely to be sustained if they address
diseases for which effective control or prevention measures
Above all, a surveillance system should include not only a
capacity for collection and analysis of data, and dissemination of
information, but also direct links to public health programmes.
An example where this has been done successfully is in
California, US, where public campaigns against tobacco have
been associated with decreasing mortality rates of lung cancer.11
The challenge of stroke surveillance
Stroke meets many of the criteria that warrant the establish-
ment of a surveillance system: it is a major public health
problem, it is largely preventable and it is a disease that has
a major impact in all countries. Reports of incidence rates for
stroke mostly come from communities in developed countries
and, even there, in communities with well-established epidemio-
logical traditions, there is a shortage of studies that are able to
provide data on temporal trends in the incidence of stroke.12
Different methodological approaches hamper the comparison of
rates over time and between populations. The WHO MONICA
Project (MONItoring trends and determinants in CArdio-
vascular disease), initiated in the early-1980s, was an attempt
to overcome some of these difficulties and to understand the
reasons for the trends in cardiovascular mortality.13It has
yielded substantial information about the burden of ischaemic
heart disease and stroke in the communities of the participating
centres, although many only included subjects aged up to 65
years and the remainder only those aged up to 75 years, thereby
omitting the age groups where the burden of stroke is
greatest.14–16Strict definitions and tight control of the quality
of the data collection have permitted detailed analyses of trends
over time and comparisons between the populations studied.17,18
Such a system is, nevertheless, not appropriate in countries
with limited resources, including those that have no access to
information about cause of death. WHO has recognised that if
ongoing surveillance of stroke is to become a reality, there is a
need to develop simple, sustainable systems that can be used
widely to provide further within-country comparisons as well as
allow a measure of between-country differences.
The framework for a stroke surveillance
A stroke surveillance system includes many different aspects of
stroke in the community. Measures of incidence, case-fatality,
and mortality are essential for the planning and evaluation of
preventive strategies and allocation of health resources. More
elaborate information includes mode of treatment, functional
level before and after stroke, and subtype of stroke (ischaemic
stroke, primary intracerebral haemorrhage, or subarachnoid
For this reason, a stepwise approach to surveillance of stroke
is suggested (Figure 1). There are three different groups of
stroke patients: those admitted to hospital (or other health
facilities), fatal events occurring out of hospital, and non-fatal
events managed outside of a hospital facility. Stroke patients
in hospital are the easiest to identify, and non-fatal non-
hospitalized cases the most difficult to identify. It is through the
completion of each of the three steps that the system provides
basic epidemiological estimates. Step 1 gives frequency of hos-
pital admission due to stroke, inclusion of step 2 would enable
calculation of mortality rates, whereas completion of step 3
would provide incidence rates and the case-fatality.
Stroke patients admitted to hospital
Within the framework of surveillance, data on patients admitted
to hospital include age, sex, identification of whether it is a
first-time or recurrent stroke, and vital status (dead or alive) at
discharge from hospital, the core data. Although patients with
stroke admitted to hospital may constitute a highly selected
group of all cases in the community, the information will never-
theless give basic estimates of costs, need for rehabilitation pro-
grammes, and severity of stroke for a given community. It will
also act as a marker at a local level for increases in stroke burden
if admission practices are taken into consideration.
Case-fatality is often expressed according to vital status
28 days after stroke onset, but this usually requires follow-up
after discharge and may be difficult to accomplish in countries
where the infra-structure and the communication technologies
are only scarcely developed. A shorter observation period of
10 days is therefore suggested for the core data set as it is easier
to ensure completeness of data collection.
Countries with greater resources might prefer to expand
measures to include vital status at 28 days, some measure of
functional level, information on prevalence of risk factors,
and medical treatment given during the stay in hospital and
prescribed at discharge; this constitutes the expanded version of
the hospital data (Figure 1). The information obtained at this
level is thus more complex than the ‘core’ data. Until this point
of the stepwise approach, access to expensive technological
facilities is not required. Classification of the stroke as either
ischaemic or haemorrhagic requires advanced technical equip-
ment, and constitutes the most sophisticated level of data
collection, the comprehensive hospital data. Such information is
of interest as the proportions of haemorrhagic and ischaemic
strokes vary considerably between countries and may have an
impact on strategies for prevention and management. Technical
INTERNATIONAL J OURNAL OF EPIDEMIOLOGY
investigations also provide information on the prevalence of
other conditions, for example infectious diseases, that may mimic
Fatal stroke events in the community
Fatal events that occur in the community, that is without
contact with a hospital, or clinic, constitute the next element in
the stepwise approach to stroke surveillance. Expanding case
ascertainment to include fatal stroke events is warranted to
define the numerator for calculating the mortality rate in the
community. Two methods can be used, namely case identification
from death certificates or verbal autopsy.
Reports from developed countries indicate that a large
proportion of fatal stroke events occur without admission to
health facilities.16In these settings access to a registry of death
certificates can be a key method for ascertaining fatal cases. In
many developed countries physicians are responsible for issuing
death certificates, and although there are differences between
coding practices between regions, death registrations are the
major source of routine data and have been shown to be useful
for measuring trends in mortality. The quality may be further
increased by scrutinizing patient files, records, and interviews
with carers in order to ensure that the symptoms before death
were consistent with the definition of stroke. While this source
of information should be used whenever possible, in many
countries death certificates are either not routinely issued or
their validity is doubtful.
Verbal autopsies are increasingly being used to monitor the
distribution of death by cause in places where medical certi-
fication of cause of death is uncommon. The method involves
interviewing close relatives or caretakers of the deceased and
classifying causes of death on the basis of the interview.20To
date most studies employing verbal autopsies have described
infant and maternal causes of mortality but the method has
recently been extended to a study of mortality from stroke in
a developing country21(Reddy KS—personal communication).
Validation studies, using hospital events as the reference category,
have demonstrated that verbal autopsy could be an important
way to obtain information on adult cause of death22until better
systems can be established.
Information on cause of death is also available through necropsy
reports. However, in many countries the necropsy rates are
decreasing, and in several places they are not done because of
traditional, religious or other reasons. It is therefore insufficient
to base an estimate of mortality on this fraction of stroke deaths
alone, but the information should be added where it is available.
Non-fatal stroke events in the community
The final level in the surveillance system includes stroke patients
who are cared for entirely within the community. Identifying
these cases is often difficult but is important as they may
constitute a large fraction of relevant events.23For example, the
proportion of non-fatal stroke cases diagnosed and treated out
of the hospital was up to 16% in the MONICA study.16Further-
more, it is only when these cases are included that the incidence
rate and case-fatality for stroke can be calculated accurately.
Three different methods are suggested for obtaining these
data. The first involves contact with general practitioners,
a well-known approach already used in several community-
based stroke studies in developed countries.23,24If all general
practitioners in the study area cannot be included, a random
sample can be used.25It is then possible to derive an estimate of
how many affected patients have not been admitted to hospital
once allowance is made for the sampling and response fractions.
This approach is valid, although it requires that the study
population has easy access to medical practitioners or primary
care practitioners, which may not be the case in developing
SURVEILLANCE OF STROKE
Figure 1 A step-wise approach to stroke surveillance
Alternative methods for obtaining information on the
number of non-fatal events treated out of health facilities are
therefore required, and the capture-recapture method may be a
suitable approach.26Participants in a population survey would
be asked a screening question about recent medical diagnoses
of stroke, and the corresponding register of cases managed
in hospital during the same period is then checked. The final
estimate for non-fatal cases occurring in the whole population
is derived by adjusting for the mismatch and allowing for
the response fraction in the population survey. This method is
feasible when integrated with other survey activities, for example,
a population census or a risk factor survey, to decrease the ex-
pense of administering the questionnaire. While this technique
is promising, only a few investigators have used the capture-
recapture technique for stroke,27and there remain uncertainties
about independence of data sources and correct identification of
A third approach to determine the number of patients with
stroke managed in the community is to estimate the number
of people with hemiplegia/hemiparesis and the time since the
onset. Sudden onset of hemiplegia or hemiparesis in adults is, to
a great extent, limited to stroke and head injury and these are
easily distinguished. Studies from different developing countries
have already provided information on the prevalence of
hemiplegia following stroke.29–31If the incidence of residual
hemiplegia following stroke and the time course of survival of
affected patients are constant within a given community, trends
in the prevalence of hemiplegia will reflect trends in the in-
cidence of stroke. It should be noted that the rates are likely to
be an underestimate as some minor strokes are likely to be missed.
Nevertheless, when combined with the rest of the stroke sur-
veillance system, it will provide data to improve estimates of the
Calculations of epidemiological estimates are based on the num-
ber of events occurring in the study population, but this may be
difficult to obtain if a reliable estimate of the source population
(the denominator) is not available. It should be noted that in
communities where it is not possible to get information on the
size of the population, the hospital step of the stroke surveillance
system may still be used. However, the remaining two steps
assume the availability of an estimate of the size of the source
One of the first issues in setting up surveillance studies is
therefore to specify and describe the population in which the
study is to take place. The selection criteria are of paramount
importance as the data and interpretation of the results will
depend on what part of the population is included. To provide a
reliable estimate of the occurrence of stroke, community-based
programmes are recommended. Inclusion of the entire popu-
lation in a country is usually not possible, and it may therefore
be better to identify different regions in the country for the
survey. Often there are differences between urban and rural
districts with respect to exposure to risk factors, treatment of
predisposing diseases, for example hypertension, and access
to health facilities. An ideal surveillance programme therefore
should include a random, representative sample of the total
population, including both urban and rural areas.
The precision of the calculated rates and proportions is in-
versely related to the size of the study population, and the num-
ber of events. In contrast, expenses of the study are positively
correlated to the total size of the source population in which
the surveillance is to take place. It is feasible to restrict the
programme to age groups where stroke starts to occur. Strokes
occur in developing countries at a much earlier age than in
developed countries.21Even so, most strokes happen in people
aged more than 45 years, and this may be set as the lower age
limit. Elderly people often have multiple co-morbidities, which
increase the uncertainty of assigning one specific disease as the
primary cause of death.32It may therefore be feasible to set the
upper age limit to 85 years.
Evaluation of preventive interventions
Many non-communicable diseases, including stroke, are the
end result of exposure to risk factors that may have been present
for several decades. However, in contrast to the long latency
period (time from exposure to development of disease), there
may be a relatively rapid reverse in incidence once exposure
to risk factors is reduced. Several clinical trials and numerous
epidemiological studies have shown that stroke is, to a large
extent, preventable.33Level of blood pressure, diabetes and
smoking have been associated with the lifestyle of developed
countries, but these risk factors already have an immense
impact on health in developing countries.34,35Epidemiological
studies have demonstrated that the risk of stroke decreases
rapidly in smokers who quit smoking.36,37Blood pressure is
another important risk factor for stroke that is amenable to
control and where adequate intervention is known to reduce
the incidence of stroke.38Changes in the exposure of these risk
factors are therefore likely to be reflected in changes in the
stroke occurrence rate. This suggests that a surveillance system
for stroke can become a valuable tool in evaluating preventive
interventions aimed at tobacco and blood pressure.39
Surveillance of risk factors for stroke
While information from a disease register indicates the mag-
nitude of the problem at present and provides data for health
policy makers, the prevalence and extent of exposure to risk
factors in the population is the strongest indicator of the future
burden of disease. Therefore, wherever possible the develop-
ment of a stroke surveillance system should be accompanied by
the creation of a similar system for measuring key risk factors in
the same population.
As the level of economic development, and hence available
financial and human resources varies between countries, a
system that can be adapted to local needs and resources is
necessary. Surveillance of major risk factors for stroke, like that
of stroke itself, can be approached in a stepwise fashion. The
recommended surveillance measures are categorized according
to the degree of difficulty in obtaining them; self-reported or
verbal responses provide the core level, followed by physical
examinations requiring basic field studies, and finally, inclusion
of measures that require access to laboratories.
Many risk factors for non-communicable diseases have been
described. The focus in the risk factor surveillance system should
be on those that are modifiable and which are known to result
INTERNATIONAL J OURNAL OF EPIDEMIOLOGY
in changes in the occurrence of the disease. The basic package
of measures should include demographic data, smoking, physical
activity, alcohol consumption, simple questions on nutrition
based on self-report. However, many countries will be able to
incorporate physical examination which can be accomplished at
the next step of the stepwise approach of risk factor surveil-
lance. At this level, information on demographic data, smoking,
physical activity, alcohol consumption and nutrition would
be repeated and in addition weight and height are estimated
using a balance beam and tape or stadiometer. Furthermore,
data on girth and blood pressure are measured. The final step
would include estimates based on laboratory examinations.
At this level of surveillance data on demography, smoking,
physical activity, alcohol, nutrition, weight, girth, and blood
pressure may be identical to that collected for the physical
examination level. However, more sophisticated measures may
also be included such as high density lipoprotein (HDL) choles-
terol and serum triglycerides, together with more elaborate
measures of smoking, alcohol consumption, blood cholesterol
and blood glucose as options.
One of the goals with both surveillance systems is to enable
comparisons within and between regions. It is known from
the MONICA study that the quality of data varies between
countries,16and a system that is to be set up in developed as
well as developing countries is likely to face the same problem.
In the stroke surveillance system the validity of the diagnosis
may differ. In some countries infectious diseases such as HIV/
AIDS, syphilis and tuberculosis may be relatively common causes
of neurological symptoms that mimic those of cerebrovascular
disease.40Patients admitted to a hospital with signs of stroke are
likely to undergo clinical and paraclinical examinations which
will increase the accuracy of the data, whereas only few patients
managed in the community may be thoroughly examined.
For the risk factor surveillance system, differences between the
surveillance sites are also likely to occur, including variations
related to response rates and in obtaining the physical measure-
ments, as well as differences between laboratories. For both
systems, when data become more complex the accuracy is likely
to decrease. This is a flaw that will be important to keep in mind
when interpreting the results. International quality control of
the data, as was undertaken in the MONICA study, is beyond
the scope of many countries. Instead, efforts should be directed
at improving the quality of data collected locally.
With many countries experiencing an ageing population,
especially those in rapid economic transition, prevention of
non-communicable diseases such as stroke is of paramount
importance. Primary prevention is central as an efficient and
inexpensive way to reduce the disease burden, but this relies on
epidemiological data to identify prevention priorities. Surveil-
lance systems are useful tools for obtaining this information and
adherence to standards enables national and international
comparisons. However, differences in capacity would exclude
many less wealthy countries from participation if the system is
unable to adjust to local needs. The WHO surveillance systems
for stroke and its risk factors are designed so that they are
flexible and can be used in different settings.
We acknowledge Terry Dwyer who has contributed substantially
to the development of the risk factor surveillance system. We
would also like to thank Regina Winkelmann for valuable
comments and suggestions, and Gael Kernen for assistance.
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