1. The prevalence of schizophrenia: a systematic review Sukanta Saha David Chant Joy Welham John McGrath Art work from the QCMHR Collection

2. Why 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

3. Systematic 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

4. Systematic 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

5. Outline 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

6. Methods Electronic data searches –Medline, PsychoInfo, Embase, LILAC 1965-2002 inclusive Index terms: –(schizo* OR psycho*) AND (incidence OR prevalence)

7. Methods 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

8. Discrete 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

9. Filters 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

10. The taxonomy of prevalence Point Period Lifetime Lifetime Morbid Risk (LMR) Not otherwise specified (NOS) Inpatient-Census- Derived rates

11. Results 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)

12. Detailed search strategy n Electronic databases =1112 From bibliography = 144 Contact with authors = 53 n Total studies =1309 n Not prevalence =561 n Review/commentary =190 n Potential Prevalence Studies =388 Awaiting assessment/ unobtainable =12 Incidence study (158+6)=164

13. Potential Incidence/Prevalence studies = 388 Not population = 87 Not population based = 87 Insufficient data = 48 n LOTE n Prevalence n = 17 Total Prevalence Studies=235- (26+19) = 191 Complete Overlap = 26 Prevalence studies = 219 Follow up/other studies = 17 Prison Studies = 19 + Special Group studies= 44Migrant studies= 14 Core studies= 133

14. RegionNationsStudies North America231 Central and South America 45 Europe1884 Africa69 Asia1142 Australasia413

15. LOTE Papers (7 Languages) Chinese (3) French (2) German (4) Italian (1) Japanese (3) Russian (3) Spanish (1) Total = 17

16. Prevalence of Schizophrenia: Combined rates for persons Number of rates = 141 Median value = 3.3 per 1000

17. Prevalence of Schizophrenia per 1000 (persons) n10%Median90%Mean Point Period Lifetime NOS Combined

18. Prevalence of Schizophrenia per 1000 (persons) n10%Median90%Mean Point242.94.310.05.8 Period Lifetime NOS Combined

19. Prevalence of Schizophrenia per 1000 (persons) n10%Median90%Mean Point242.94.310.05.8 Period441.33.48.55.7 Lifetime NOS Combined

20. Prevalence of Schizophrenia per 1000 (persons) n10%Median90%Mean Point242.94.310.05.8 Period441.33.48.55.7 Lifetime312.14.011.05.6 NOS Combined

21. Prevalence of Schizophrenia per 1000 (persons) n10%Median90%Mean Point242.94.310.05.8 Period441.33.48.55.7 Lifetime312.14.011.05.6 NOS421.42.74.74.5 Combined

22. Prevalence of Schizophrenia per 1000 (persons) n10%Median90%Mean Point 242.94.310.05.8 Period 441.33.48.55.7 Lifetime 312.14.011.05.6 NOS 421.42.74.74.5 Combined 1411.53.310.05.4

23. Lifetime Morbid Risk per 1000 (persons) n10%Median90%Mean Lifetime Morbid Risk 273.17.227.111.9

24. Inpatient Census Derived rate per 1000 (persons) n10%Median90%Mean Inpatient census derived rate 1080.12.410.06.5

25. Prevalence 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)

26. Sex 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

27. Male:female rate ratio Median rate ratio = 1.16

28. Male:female Rate ratio 31 studies 100 rate ratios Median (10-90% quantiles) 1.4 (0.9 to 2.4) Incidence of schizophrenia

29. Male:female rate ratio by nation economic status

30. Migrant vs Native born Rate Ratio (persons) Number of rate ratios = 10 Median rate ratio = 1.8 Rate ratio

31. Prevalence by Quality Score Median value (number of rates) Lower = 2.9 (54) Middle = 3.0 (41) Upper = 5.2 (46)

32. Conclusions There is a wealth of data Most of the distributions are ‘data rich’ (informative) Not normally distributed - skewed by higher values

33. Conclusions 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

34. Conclusions Males = females for prevalence Developing nations lower prevalence female excess

35. Acknowledgements Interpreters ~ 10 Authors who provided information ~ 31 Stanley Medical Research Institute For our website for full dataset: www.qcmhr.uq.edu.au/epi