Sukanta Saha David Chant Joy Welham John McGrath

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Sukanta Saha David ChantJoy WelhamJohn McGrath
A systematic review of the prevalence of
schizophrenia
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Schizophrenia is comprised of groups of brain
disorders characterized by symptoms such as
hallucinations, delusions, disorganized
communication, poor planning, reduced motivation,
and blunted affect. While the incidence of the
disorder is relatively low (median value 15.2 per
100,000 persons per year), the condition is a
major contributor to the global burden of
disease. The substantial burden of
schizophrenia results from a) its typical onset
in early adulthood, and b) despite optimal
treatment, about two thirds of affected
individuals have persisting or fluctuating
symptoms. Understanding the prevalence of
schizophrenia has important implications for both
health service planning and risk factor
epidemiology.
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Aims

• To systematically identify and collate studies of
  the prevalence of schizophrenia
• To summarize variation in time, place and person
  by examining the distribution of these estimates
  of prevalence
• To explore factors which may influence prevalence
  estimates

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Outline

• Types of prevalence
• Research questions
• Methods
• Key results
• Caveats and Conclusions

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Ways to measure prevalence
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The prevalence of schizophreniaResearch
questions

• Different types of prevalence
• Sex difference
• Males vs females
• Migrant status
• Migrants vs native born
• Urbanicity
• Urban born vs rural born
• Developed vs developing countries
• Quality of methods

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Types of prevalence studies

• Population-based groups
• Core studies
• Inpatient-Census-Derived data
• Population sub-groups
• Migrant studies
• Other special groups

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Methods systematic review

• Electronic data search
• Medline, PsychoInfo, Embase, LILAC
• 1965-2002 inclusive
• (schizo OR psycho) AND (incidence OR
  prevalence)
• Review article bibliography
• Wrote to authors
• Screen abstract and reviewed papers to cull
  irrelevant citations

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Estimates and discrete data

• Non-overlapping
• Sex Male, Female
• Overlapping
• Examples
• Age eg. all ages or age 15-54
• Diagnosis eg. Catego S or SPO clinical
• Site overlap eg. Denmark or Copenhagen
• Epoch overlap eg. 1990-92 or 1989-91

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Data analysis example cumulative distribution
Rate per 1,000
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Results
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Results (2)

• After review
• 188 studies from 46 countries
• 1,721 prevalence estimates
• 154,140 potentially overlapping cases
• Types of studies
• Core studies 132
• Migrant studies 15
• Other special groups 41

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Core Prevalence Studies Point prevalence

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Core Prevalence Studies Period prevalence

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Core Prevalence Studies Lifetime prevalence

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Core Prevalence Studies Lifetime Morbid Risk

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Core Prevalence Studies Unspecified

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Core Prevalence Studies Inpatient census
prevalence

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Sex differences
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Male female estimate ratio

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Migrant statusmigrantnative population ratio
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Urban-rural differences
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Economic status of country
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Economic status of country Malefemale
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Quality score
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Other special groups
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Key findings

• Like incidence, the prevalence of schizophrenia
  is variable across sites/groups
• -it ranges from 3-7 per 1,000 persons, depending
  on the type of prevalence estimate
• -is higher in migrants vs native born
• Also countries from the developing world have a
  lower prevalence of schizophrenia
• Unlike incidence, the prevalence of schizophrenia
• - does not vary between the sexes - but there is
  substantial variation between sites
• is not higher in urban versus rural settings

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Discussion

• Comparisons in systematic reviews should be
  planned, based on directional hypotheses
  limited to a reasonable number
• Systematic reviews are best suited to
  hypothesis-generation
• Geographical boundaries are administrative

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Conclusions
Many people with schizophrenia have persistent
symptoms It is estimated that even given the best
interventions, 3/4 of the burden of schizophrenia
would remain This demands additional applied and
basic etiological research Paradoxes like the
differences between incidence and prevalence in
sex differences and urban-rural settings demand
further research