Title: The prevalence of schizophrenia: a systematic review
1The prevalence of schizophrenia a systematic
review
- Sukanta Saha
- David Chant
- Joy Welham
- John McGrath
Art work from the QCMHR Collection
2Why is prevalence important?
- Estimate the burden of a disorder
- Administration - service planning
- Provides information about the interaction
between incidence and course of the illness - Gradients in the prevalence of a disorder can
help generate risk factors
3Systematic reviews
- Traditional methods
- narrative reviews
- Systematic reviews
- A standardized, rigorous process of finding
literature and extracting data in a way that
minimizes bias and errors - with or without meta-analysis
4Systematic reviews
- Past reviews
- Torrey 1987 (narrative)
- Jablensky - several reviews (narrative)
- Goldner et al. 2002 (systematic review with
meta-analysis) - 8 studies (1980-2000)
- Lifetime prevalence varied 13 fold
- Distribution of rates versus pooled rate
5Outline
- Distribution of various types of prevalence
- Median and spread of rate items
- Sensitivity analyses
- economic status of country
- quality score
- Male-female rate ratio
- Sensitivity analysis by economic status of
country - Migrant-Native born rate ratio
6Methods
- Electronic data searches
- Medline, PsychoInfo, Embase, LILAC
- 1965-2002 inclusive
- Index terms
- (schizo OR psycho) AND (incidence OR prevalence)
7Methods
- Review article bibliography
- Writing to authors
- Posters at Whistler and Davos conferences
- Screen abstract to cull irrelevant citations
- Order articles for review and data extraction
8Discrete rates
- One study may generate multiple rates
- ECA study (60 rates)
- 5 age gr
- 4 rate types
- 2 sexes
- Discrete (non-overlapping)
- Male 2.1 per 1,000
- Female 1.5 per 1,000
- Overlapping
- site and epoch
- Age groups
- Diagnostic groups
9Filters for overlapping studies
- Several filters to identify discrete data
- Filters are operationalised and explicit
- Most informative rule
- Entire nation preferred over regions
- All ages preferred over age-specific
10The taxonomy of prevalence
- Point
- Period
- Lifetime
- Lifetime Morbid Risk (LMR)
- Not otherwise specified (NOS)
- Inpatient-Census-Derived rates
11Results
- Archived 1112 articles, book chapters or theses.
- 85 identified via electronic sources
- 11 from bibliography
- 4 from authors
- Interim list sent to 80 authors
- Replies from 31 authors (New articles, theses,
bibliographies)
12Detailed search strategy
- Electronic databases 1112
Awaiting assessment/ unobtainable 12
Incidence study (1586)164
- Potential Prevalence Studies 388
13Potential Incidence/Prevalence studies 388
Not population based 87
Insufficient data 48
Follow up/other studies 17
Prevalence studies 219
Complete Overlap 26
Prison Studies 19
Total Prevalence Studies235- (2619) 191
Special Group studies 44
Migrant studies 14
Core studies 133
14Region Nations Studies
North America 2 31
Central and South America 4 5
Europe 18 84
Africa 6 9
Asia 11 42
Australasia 4 13
15LOTE Papers (7 Languages)
- Chinese (3)
- French (2)
- German (4)
- Italian (1)
- Japanese (3)
- Russian (3)
- Spanish (1)
- Total 17
16Prevalence of SchizophreniaCombined rates for
persons
Number of rates 141 Median value 3.3 per
1000
17Prevalence of Schizophrenia per 1000 (persons)
n 10 Median 90 Mean
Point
Period
Lifetime
NOS
Combined
18Prevalence of Schizophrenia per 1000 (persons)
n 10 Median 90 Mean
Point 24 2.9 4.3 10.0 5.8
Period
Lifetime
NOS
Combined
19Prevalence of Schizophrenia per 1000 (persons)
n 10 Median 90 Mean
Point 24 2.9 4.3 10.0 5.8
Period 44 1.3 3.4 8.5 5.7
Lifetime
NOS
Combined
20Prevalence of Schizophrenia per 1000 (persons)
n 10 Median 90 Mean
Point 24 2.9 4.3 10.0 5.8
Period 44 1.3 3.4 8.5 5.7
Lifetime 31 2.1 4.0 11.0 5.6
NOS
Combined
21Prevalence of Schizophrenia per 1000 (persons)
n 10 Median 90 Mean
Point 24 2.9 4.3 10.0 5.8
Period 44 1.3 3.4 8.5 5.7
Lifetime 31 2.1 4.0 11.0 5.6
NOS 42 1.4 2.7 4.7 4.5
Combined
22Prevalence of Schizophrenia per 1000 (persons)
n 10 Median 90 Mean
Point 24 2.9 4.3 10.0 5.8
Period 44 1.3 3.4 8.5 5.7
Lifetime 31 2.1 4.0 11.0 5.6
NOS 42 1.4 2.7 4.7 4.5
Combined 141 1.5 3.3 10.0 5.4
23Lifetime Morbid Risk per 1000 (persons)
n 10 Median 90 Mean
Lifetime Morbid Risk 27 3.1 7.2 27.1 11.9
24Inpatient Census Derived rate per 1000 (persons)
n 10 Median 90 Mean
Inpatient census derived rate 108 0.1 2.4 10.0 6.5
25Prevalence by Country Group
Median rate per 1000 (number of rates) Least
Developed Countries 2.6 (19) Emerging 4.2
(25) High income 3.3 (97)
26Sex differences in the prevalence of schizophrenia
- No significant sex difference in the prevalence
of schizophrenia - Median (number of rates)
- Males 3.8 (61)
- Females 3.2 (62)
- F 0.84, p 0.36
27Malefemale rate ratio
Median rate ratio 1.16
28Incidence of schizophrenia
Malefemale Rate ratio 31 studies 100 rate
ratios Median (10-90 quantiles) 1.4 (0.9 to
2.4)
29Malefemale rate ratio by nation economic status
30Migrant vs Native born Rate Ratio (persons)
Number of rate ratios 10 Median rate ratio
1.8
31Prevalence by Quality Score
Median value (number of rates) Lower 2.9
(54) Middle 3.0 (41) Upper 5.2 (46)
32Conclusions
- There is a wealth of data
- Most of the distributions are data rich
(informative) - Not normally distributed - skewed by higher
values
33Conclusions
- Median overall prevalence rate 3.3 per 1000
- Median LMR 7.2 per 1000
- 2 out of every 300 people
- Spread of the data
- 10 90 quantiles
- Point 3.4 fold
- LMR 9 fold
34Conclusions
- Males females for prevalence
- Developing nations
- lower prevalence
- female excess
35Acknowledgements
- Interpreters 10
- Authors who provided information 31
- Stanley Medical Research Institute
For our website for full dataset
www.qcmhr.uq.edu.au/epi