Xiang et al’s study looks at demographics and prevalence of schizophrenia in China. This is an ambitious study looking at 5926 people in Beijing. The authors note that two studies published in chinese journals noted a lifetime prevalence of schizophrenia of 0.57% in 1982 and 0.66% in 1993 (which includes the twelve region psychiatric epidemiological study work group 1986). As with any study there is selection bias of one form or another. In this study, some of the practicalities of collecting data mean that prevalence may have been underestimated. For instance being willing to participate in the study may be less likely in those with paranoid beliefs whilst the ability to cohabit with the family may be influenced by a marked psychosis. Nevertheless the large sample size and the process of approaching households is an enormous task which should not be underestimated.
The researchers used the Composite International Diagnostic Interview-Version 1.0 (CIDI 1) which produces ICD-10 codes. Whilst as many as 102 psychiatrists completed the questionnaires, the inter-rater reliability using the kappa value was 0.795 (1 is the highest possible rating for reliability and suggests equivalent scoring – thus the value here is quite high and suggests good inter-rater reliability). In addition to the ICD-10 codes, the researchers obtained demographic data. The researchers then examined the relationship between schizophrenia and each of the other variables using a multiple regression analysis to control for the remaining variables in each case.
The researchers found that the lifetime prevalence was 0.49% (0.44% for men and 0.55% for women). For rural areas the prevalence was 0.39% and in urban areas it was 0.57%. The odds ratio for each demographic was then calculated (people with schizophrenia v people without). Significant results (p<0.05) were found for marital status, family history of schizophrenia, higher income and living in rural areas. Although these factors were described as protective, the cross-sectional nature of the study mean that they should be considered as associations.
A meta-analysis of prevalence studies by Goldner in 2002 produced a figure of 0.55%. These study findings are very similar which suggests that cultural differences may be less influential for the aetiology. The earlier study on depression in China suggested a difference of several hundred fold compared to western studies – although this was later revised in the light of further studies.
Although there was a higher prevalence of schizophrenia in women, this was not-significant in this study. However the previous studies in China showed similar findings which is the reverse of those found in Western studies. This finding certainly merits further attention. The increased prevalence in Urban areas replicates findings in Western studies. Just under 10% of people with schizophrenia in this study had attempted suicide compared to 1.6% for those without. 58% of people with schizophrenia had received treatment compared to figures of 80% reported in the USA.
This is a valuable study and the authors write that it is to the best of their knowledge the first prevalence study of schizophrenia using standardised diagnostic criteria in urban and rural areas in China.
The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor.