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Population Surveys Scopes , Prevalence , Incidence , Health Registries. Ettore Beghi Institute for Pharmacological Research Mario Negri, Milano, Italy. SCOPE OF POPULATION SURVEYS. Measure prevalence Measure incidence Measure mortality Identify cases for case-control studies

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Population surveys scopes prevalence incidence health registries

PopulationSurveysScopes, Prevalence, Incidence, HealthRegistries

Ettore Beghi

InstituteforPharmacologicalResearch Mario Negri, Milano, Italy


Scope of population surveys
SCOPE OF POPULATION SURVEYS

  • 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
ANATOMY OF A POPULATION SURVEY

  • Definitionof the studypopulation

  • Definitionofdisease

  • Case ascertainment (prevalence, incidence and mortality)

  • Calculationofepidemiologicalindexes

  • Distributionbytime, place & person



How to define a population
HOW TO DEFINE A POPULATION POPULATION

  • Geographicboundaries - Residency - Istituzionalization - Migration

  • Temporalboundaries - Prevalenceperiod (point, period, lifetime) - Incidenceperiod


Measures of disease frequency
MEASURES OF DISEASE FREQUENCY POPULATION

  • 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 AND INCIDENCE POPULATION

Prevalence = Incidence

x average duration

Incidence

Migrating

in

Migrating

out

Prevalence

Death

Recovery


Sources of neurological diseases in epidemiological studies
SOURCES OF NEUROLOGICAL DISEASES IN EPIDEMIOLOGICAL STUDIES POPULATION

  • Hospital records

  • Ambulatoryrecords

  • Electrophysiological (EMG) records

  • Generalpractitioners’ files

  • Disabilityrecords

  • Layassociations

  • Tertiarycenters

  • Death certificates

  • Diagnosisrelatedgroups (DRGs)

  • Diseaseregistries


Migraine is a heterogeneous and ill defined clinical condition
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
MIGRAINE WITHOUT AURA (IHS, 1988) CONDITION

  • A. At least 5 attackswithcriteria B-D

  • B. Attackslasting 4-72 hr (no or poor treatment)

  • C. Headachewith at leasttwofeatures: - Unilateral - Pulsating - Moderate or severe

  • D. At leastoneamong: - Nausea and/or vomiting - Photophobia and/or phonophobia

  • E. At leastoneof the following: - Otherdisturbancesexcludedbyhx and examination - Otherdisturbancesexcludedbydiagnostictests - Otherdisturbances, butmigraineattacksverified


Change in the prevalence of migraine when varying the number of ihs diagnostic criteria
CHANGE IN THE PREVALENCE OF MIGRAINE WHEN VARYING THE NUMBER OF IHS DIAGNOSTIC CRITERIA

Merikangaset al, 1990


Epilepsy and epileptic seizures
EPILEPSY AND EPILEPTIC SEIZURES NUMBER OF IHS DIAGNOSTIC CRITERIA

  • EPILEPSY= Clinicalconditioncharacterizedbyrepeatedunprovokedseizures

  • UNPROVOKED SEIZURE= Seizureoccurring in the absenceofknownprecipitants; itmayoccur at the presenceof a non-recent CNS injury

  • ACUTE SYMPTOMATIC SEIZURE = Seizureoccurring in closetemporalrelationshipwithan acute CNS insult


Epilepsy active in remission definitions
EPILEPSY, ACTIVE & IN REMISSION NUMBER OF IHS DIAGNOSTIC CRITERIADefinitions

  • 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: absenceofseizuresfor 2 or 5 yearswithoutAEDs


Acute symptomatic seizures interval from precipitating factor
ACUTE SYMPTOMATIC SEIZURES NUMBER OF IHS DIAGNOSTIC CRITERIAInterval from precipitating factor

Epidemiology Task Force, Epilepsia 2009


Epidemiological indexes of epilepsy in industrialized countries
EPIDEMIOLOGICAL INDEXES OF EPILEPSY IN INDUSTRIALIZED COUNTRIES

  • IncidenceEpilepsy 29-53 100,000/yrEpilepsy+singleseizures 73-86 Acute symptseizures 20-30 Status epilepticus 10-40

  • Cumulative incidence 1-3%

  • PrevalenceActiveepilepsy 5-8 x1,000 Lifetime 15-50

  • Mortality 1-4 x100,000/yr

  • SMR 2-3


DeCarli COUNTRIES, LancetNeurol

2003: 2:15


Prevalence of cognitive impairment according to clinical definition
PREVALENCE OF COGNITIVE IMPAIRMENT ACCORDING TO CLINICAL DEFINITION

DeCarli, LancetNeurol

2003: 2:15


Problems regarding the diagnosis of polyneuropathy
PROBLEMS REGARDING THE DIAGNOSIS OF POLYNEUROPATHY DEFINITION

  • 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
Polyneuropathy DEFINITION in the ElderlyPrincipalSymptoms

  • 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
POLYNEUROPATHY IN THE ELDERLY DEFINITION Validityof the screening questions

Monticelli et al, Neuroepidemiology 1993


Polyneuropathy in the elderly inter rater agreement kappa statistic
POLYNEUROPATHY IN THE ELDERLY DEFINITION Inter-rater agreement (kappa statistic)

Monticelli et al, Neuroepidemiology 1993


El escorial criteria for the diagnosis of als
EL ESCORIAL CRITERIA FOR THE DIAGNOSIS OF ALS DEFINITION

  • 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 als1
EL ESCORIAL CRITERIA FOR THE DIAGNOSIS OF ALS DEFINITION

  • 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

  • SUSPECTED ALS - LMN signs in 2 or more regions

Source: J Neurol

Sci 1994; 124

(suppl): 96-107


Disease registries
DISEASE REGISTRIES DEFINITION

  • 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
EXPLANATIONS FOR HIGHER AND MORE HOMOGENEOUS RATES IN EUROPEAN REGISTRIES

  • Prospective inception of cases

  • Multiple sources

  • Fairly complete case ascertainment

  • Continuous surveillance

  • Use of the same diagnostic criteria


Objectives of a population based registry
OBJECTIVES OF A POPULATION-BASED REGISTRY EUROPEAN REGISTRIES

  • 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
PREREQUISITES FOR THE START OF A REGISTRY EUROPEAN REGISTRIES

  • Definition of the population at risk

  • Selection of the best source(s) of cases

  • Choice of the correct diagnostic criteria


Sources of cases
SOURCES OF CASES EUROPEAN REGISTRIES

  • 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
THE EURALS CONSORTIUM EUROPEAN REGISTRIES

  • Ireland 5.0M

  • Scotland 5.0M

  • Lancashire & Cumbria 1.8M

  • London 2.8M

  • Italy (all) 8.0M

  • Belgrade 2.0M

  • Madrid 1.0M

  • Limousin 0.7M

  • Germany ?

  • Russia ?

  • Israel ?

  • Total >25M


Practical recommendations to start a population based registry
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


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