Download STROKE Epidemiologia

Population Surveys
Scopes, Prevalence, Incidence,
Health Registries
Ettore Beghi
Institute for Pharmacological
Research Mario Negri, Milano,
Italy
SCOPE OF POPULATION
SURVEYS
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Measure prevalence
Measure incidence
Measure mortality
Identify cases for case-control studies
Identify exposures for cohort studies
Study familial aggregation/genetics
Screen candidates for prevention/early
treatment
ANATOMY OF A
POPULATION SURVEY
• Definition of the study population
• Definition of disease
• Case ascertainment (prevalence,
incidence and mortality)
• Calculation of epidemiological indexes
• Distribution by time, place & person
DIAGRAM OF THE IDENTIFICATION OF
A DISEASE IN THE GENERAL
POPULATION
Kurtzke, 1978
HOW TO DEFINE A
POPULATION
• Geographic boundaries
- Residency
- Istituzionalization
- Migration
• Temporal boundaries
- Prevalence period (point,
period, lifetime)
- Incidence period
MEASURES OF DISEASE
FREQUENCY
• INCIDENCE: Number of individuals in a
population that become ill in a stated period
of time
• CUMULATIVE INCIDENCE: Proportion of a
fixed population that becomes ill in a stated
period of time
• PREVALENCE: Proportion of a population
affected by a disease at a given point of time
• MORTALITY: Number of individuals in a
population died for a disease in a stated
period of time
PREVALENCE AND
INCIDENCE
Prevalence = Incidence
x average duration
Incidence
Migrating
in
Migrating
out
Prevalence
Recovery
Death
SOURCES OF NEUROLOGICAL
DISEASES IN EPIDEMIOLOGICAL
STUDIES
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Hospital records
Ambulatory records
Electrophysiological (EMG) records
General practitioners’ files
Disability records
Lay associations
Tertiary centers
Death certificates
Diagnosis related groups (DRGs)
Disease registries
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MIGRAINE IS A HETEROGENEOUS
AND ILL-DEFINED CLINICAL
CONDITION
Intensity, duration, frequency and
characteristics of attacks tend to vary in
the general population
In each patient, symptoms may vary
with time
Many individuals may have different
types of headache
Many individuals do not consult their
doctor for headache
MIGRAINE WITHOUT AURA
(IHS, 1988)
• A. At least 5 attacks with criteria B-D
• B. Attacks lasting 4-72 hr (no or poor treatment)
• C. Headache with at least two features:
- Unilateral
- Pulsating
- Moderate or severe
• D. At least one among:
- Nausea and/or vomiting
- Photophobia and/or phonophobia
• E. At least one of the following:
- Other disturbances excluded by hx and examination
- Other disturbances excluded by diagnostic tests
- Other disturbances, but migraine attacks verified
CHANGE IN THE PREVALENCE OF MIGRAINE
WHEN VARYING THE NUMBER OF IHS
DIAGNOSTIC CRITERIA
25
Moderate 2/4C,1/2D
20
Severe 2/4C,1/2D
Moderate 3/4C,1/2D
15
Severe 3/4C,1/2D
Moderate 2/4C,2/2D
10
Severe 2/4C,2/2D
Moderate 3/4C,2/2D
5
Severe 3/4C,2/2D
0
Prevalence (%)
Merikangas et al, 1990
EPILEPSY AND
EPILEPTIC SEIZURES
• EPILEPSY = Clinical condition characterized by
repeated unprovoked seizures
• UNPROVOKED SEIZURE = Seizure occurring in
the absence of known precipitants; it may occur
at the presence of a non-recent CNS injury
• ACUTE SYMPTOMATIC SEIZURE = Seizure
occurring in close temporal relationship with an
acute CNS insult
EPILEPSY, ACTIVE & IN
REMISSION
Definitions
• ACTIVE EPILEPSY: epilepsy currently
being treated or whose most recent
seizure has occurred (usually) within the
past two to five years (Thurman et al,
Epilepsia, 2011)
• EPILEPSY IN TERMINAL
REMISSION: absence of seizures for 2
or 5 years without AEDs
ACUTE SYMPTOMATIC SEIZURES
Interval from precipitating factor
CNS Insult
Timing of occurrence
Stroke, head trauma, cerebral anoxia
1 week
Cerebral infection
Positive clinical/laboratory findings
Brain abscess, cerebral tuberculoma
During treatment
HIV infection
Acute infection/metabolic disturb
Arterovenous malformation
Acute hemorrhage
Multiple sclerosis
Within 7 days of relapse
Autoimmune diseases
Symptoms/signs of activation
Neurodegenerative disorders
None identified
Epidemiology Task Force, Epilepsia 2009
EPIDEMIOLOGICAL INDEXES OF
EPILEPSY IN INDUSTRIALIZED
COUNTRIES
• Incidence
Epilepsy
Epilepsy+single seizures
Acute sympt seizures
Status epilepticus
• Cumulative incidence
• Prevalence
Active epilepsy
Lifetime
• Mortality
• SMR
29-53 100,000/yr
73-86
20-30
10-40
1-3%
5-8 x1,000
15-50
1-4 x100,000/yr
2-3
DeCarli, Lancet Neurol
2003: 2:15
PREVALENCE OF COGNITIVE
IMPAIRMENT ACCORDING TO
CLINICAL DEFINITION
DeCarli, Lancet Neurol
2003: 2:15
PROBLEMS REGARDING THE
DIAGNOSIS OF
POLYNEUROPATHY
• The majority of the available data comes
from clinical series
• The diagnosis of polyneuropathy is based
on clinical and elettrophysiological features
• Polyneuropathy includes a wide spectrum of
disorders ranging from symptomatic clinical
conditions to subclinical variants
• Diagnosis should be confirmed by a
neurologist
Polyneuropathy in the Elderly
Principal Symptoms
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Muscle cramps
Restless legs syndrome
Burning feet
Muscle pain
Problems with handling objects
Impairment of standing and gait
‘Glove’ and ‘stocking’ paresthesiae
POLYNEUROPATHY IN THE ELDERLY
Validity of the screening questions
Monticelli et al, Neuroepidemiology 1993
POLYNEUROPATHY IN THE ELDERLY
Inter-rater agreement (kappa
statistic)
Monticelli et al, Neuroepidemiology 1993
EL ESCORIAL CRITERIA FOR
THE DIAGNOSIS OF ALS
• Based on the topographical location of upper
(UMN) and lower motor neuron (LMN) signs
in 4 CNS regions, progression of these signs,
and absence of other diseases
• Degree of diagnostic certainty (definite,
probable, possible, suspected ALS) based on
a different combination of UMN and LMN
signs
Brooks, 1994
EL ESCORIAL CRITERIA FOR
THE DIAGNOSIS OF ALS
• DEFINITE ALS
- LMN and UMN signs in 3 spinal regions
- LMN and UMN signs in the bulbar region
and in 2 spinal regions
• PROBABLE ALS
- LMN and UMN signs in 2 spinal regions
• POSSIBLE ALS
- LMN and UMN signs in 1 region
- UMN signs in 2 or more regions
- LMN signs rostral to UMN signs Source: J Neurol
Sci 1994; 124
• SUSPECTED ALS
(suppl): 96-107
- LMN signs in 2 or more regions
DISEASE REGISTRIES
• Lists of diseases (or disease groups) in
well-defined populations
• Collection of data on disease burden
and identification of patients’ cohorts to
be followed for specific purposes
• For rare diseases, registries represent a
(re)source for the collection of sizable
numbers of cases for focused studies
EXPLANATIONS FOR HIGHER AND
MORE HOMOGENEOUS RATES IN
EUROPEAN REGISTRIES
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Prospective inception of cases
Multiple sources
Fairly complete case ascertainment
Continuous surveillance
Use of the same diagnostic criteria
OBJECTIVES OF A POPULATIONBASED REGISTRY
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Incidence and prevalence of the target condition
Temporal and geographic trends of the disease
Full clinical spectrum of the disease
Clinical and paraclinical markers of the disease
Practical management and socio-economic
implications of the disease
• Data banks for clinical/biological material
PREREQUISITES FOR THE
START OF A REGISTRY
• Definition of the population at risk
• Selection of the best source(s) of cases
• Choice of the correct diagnostic criteria
SOURCES OF CASES
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Hospital records
Outpatient records
Neurophysiology units’ archives
General practitioners’ files
Disability records
Lay associations’ files
ALS centers
Death certificates
Administrative files (hospital discharge
diagnoses)
THE EURALS CONSORTIUM
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Ireland
Scotland
Lancashire & Cumbria
London
Italy (all)
Belgrade
Madrid
Limousin
Germany
Russia
Israel
5.0M
5.0M
1.8M
2.8M
8.0M
2.0M
1.0M
0.7M
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Total
>25M
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PRACTICAL RECOMMENDATIONS TO
START A POPULATION-BASED
REGISTRY
Select a well-defined geographic area
Identify one or more accessible sources
Use valid and reliable diagnostic criteria
Set a network of specialists able to trace all
cases residing in the area
• Select a number of core variables to verify the
correctness of the diagnosis and define the
general profile of the disease
• Start specific studies only after preparing ad-hoc
protocols and case collection forms