Local literature bias in genetic epidemiology: an empirical evaluation of the Chinese literature

Abstract

Background: Postulated epidemiological associations are subject to several biases. We evaluated whether the Chinese literature on human genome epidemiology may offer insights on the operation of selective reporting and language biases.

Methods and findings: We targeted 13 gene-disease associations, each already assessed by meta-analyses, including at least 15 non-Chinese studies. We searched the Chinese Journal Full-Text Database for additional Chinese studies on the same topics. We identified 161 Chinese studies on 12 of these gene-disease associations; only 20 were PubMed-indexed (seven English full-text). Many studies (14-35 per topic) were available for six topics, covering diseases common in China. With one exception, the first Chinese study appeared with a time lag (2-21 y) after the first non-Chinese study on the topic. Chinese studies showed significantly more prominent genetic effects than non-Chinese studies, and 48% were statistically significant per se, despite their smaller sample size (median sample size 146 versus 268, p < 0.001). The largest genetic effects were often seen in PubMed-indexed Chinese studies (65% statistically significant per se). Non-Chinese studies of Asian-descent populations (27% significant per se) also tended to show somewhat more prominent genetic effects than studies of non-Asian descent (17% significant per se).

Conclusion: Our data provide evidence for the interplay of selective reporting and language biases in human genome epidemiology. These biases may not be limited to the Chinese literature and point to the need for a global, transparent, comprehensive outlook in molecular population genetics and epidemiologic studies in general.

Figure 1. Categorization of the Examined Genetic Association Studies

IQR, interquartile range; N, sample size (as median and interquartile range); StatSig, statistically significant at the 0.05 level.

Figure 2. Meta-Analyses of Gene-Disease Associations in a Large Number of Both Non-Chinese and Chinese Studies

Each study is shown by its odds ratio and 95% confidence intervals (CIs). The box of the point estimate is proportional to the study weight. Also shown are summary estimates by random effects calculations (diamonds). Summary estimates are obtained separately for Chinese studies indexed in PubMed (red), Chinese studies not indexed in PubMed (pink), non-Chinese studies of Asian descent populations (green), and studies of persons of non-Asian descent (blue). An odds ratio of 1 means no genetic effect, odds ratios larger than 1 mean genetic predisposition, and odds ratios less than 1 mean genetic protection.