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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

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PopulationSurveysScopes, Prevalence, Incidence, HealthRegistries

Ettore Beghi

InstituteforPharmacologicalResearch Mario Negri, Milano, Italy


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

  • Definitionof the studypopulation

  • Definitionofdisease

  • Case ascertainment (prevalence, incidence and mortality)

  • Calculationofepidemiologicalindexes

  • Distributionbytime, place & person


DIAGRAM OF THE IDENTIFICATION OF A DISEASE IN THE GENERAL POPULATION

Kurtzke, 1978


HOW TO DEFINE A POPULATION

  • Geographicboundaries- Residency- Istituzionalization - Migration

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


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

Death

Recovery


SOURCES OF NEUROLOGICAL DISEASES IN EPIDEMIOLOGICAL STUDIES

  • 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

  • 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 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

Merikangaset al, 1990


EPILEPSY AND EPILEPTIC SEIZURES

  • 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 REMISSIONDefinitions

  • 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 SEIZURESInterval from precipitating factor

Epidemiology Task Force, Epilepsia 2009


EPIDEMIOLOGICAL INDEXES OF EPILEPSY IN INDUSTRIALIZED COUNTRIES

  • IncidenceEpilepsy29-53 100,000/yrEpilepsy+singleseizures73-86Acute symptseizures20-30Status epilepticus10-40

  • Cumulative incidence1-3%

  • PrevalenceActiveepilepsy5-8 x1,000Lifetime15-50

  • Mortality1-4 x100,000/yr

  • SMR2-3


DeCarli, LancetNeurol

2003: 2:15


PREVALENCE OF COGNITIVE IMPAIRMENT ACCORDING TO CLINICAL DEFINITION

DeCarli, LancetNeurol

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 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 ELDERLYValidityof the screening questions

Monticelli et al, Neuroepidemiology 1993


POLYNEUROPATHY IN THE ELDERLYInter-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

  • SUSPECTED ALS- LMN signs in 2 or more regions

Source: J Neurol

Sci 1994; 124

(suppl): 96-107


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

  • Prospective inception of cases

  • Multiple sources

  • Fairly complete case ascertainment

  • Continuous surveillance

  • Use of the same diagnostic criteria


OBJECTIVES OF A POPULATION-BASED REGISTRY

  • 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

  • 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

  • Ireland5.0M

  • Scotland5.0M

  • Lancashire & Cumbria1.8M

  • London2.8M

  • Italy (all)8.0M

  • Belgrade2.0M

  • Madrid1.0M

  • Limousin0.7M

  • Germany?

  • Russia?

  • Israel?

  • Total >25M


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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