Article type
Abstract
Background: Meta-epidemiological studies aim to quantitatively analyze the impact of potential bias characteristics on the effect. There has been a gradual increase in the number of relevant publications. However, there is currently a lack of sample selection criteria. The research findings obtained from inappropriate research samples may be restricted in their application. The sample setting of meta-epidemiological studies is still unclear.
Objectives: The study aims to explore the sources, types, sizes, and limiting conditions of samples used in previously published meta-epidemiological studies.
Methods: PubMed and Embase were searched for meta-epidemiological studies on June 1, 2022. Two reviewers independently screened the literature and extracted relevant data.
Results: A total of 122 studies were included. Most studies (82.8%) were published in the last 10 years, and 22.9% were published in the Journal of Clinical Epidemiology. Only about one-fifth of the studies had a protocol (24.6%) and were registered (17.2%). Nearly 70% imposed restrictions on research areas, including specific disciplines (27.0%), diseases (21.3%), and interventions (14.8%), among others. The research primarily focused on exploring the impact of primary study characteristics (92.6%), while 62.3% of the studies included systematic reviews (SRs) as research samples, with 20.5% solely including Cochrane SRs. Among these, nearly 50% of the studies had sample sizes of less than 50 SRs. The most common sources for research samples were literature databases (91.0%), and 63% only searched one or two databases, with the three most frequently used being the Cochrane Library (70.3%), PubMed/MEDLINE (69.4%), and Embase (30.6%). About half of the studies (44.1%) limited the specific search time, and various limitations were applied to outcome, language, and sample size during subsequent literature screening. For 76 studies based on SRs, further restrictions were placed on the study type (23.6%), number (23.6%), and type of outcome (26.3%).
Conclusions: There was a lack of standardized sample selection criteria in the previous meta-epidemiological studies, resulting in diverse sources and types of samples. Additionally, the small sample size and various restrictions on the research samples result in insufficient representativeness. The findings derived from these studies, which were based on individually defined samples, might not be generalizable.
Objectives: The study aims to explore the sources, types, sizes, and limiting conditions of samples used in previously published meta-epidemiological studies.
Methods: PubMed and Embase were searched for meta-epidemiological studies on June 1, 2022. Two reviewers independently screened the literature and extracted relevant data.
Results: A total of 122 studies were included. Most studies (82.8%) were published in the last 10 years, and 22.9% were published in the Journal of Clinical Epidemiology. Only about one-fifth of the studies had a protocol (24.6%) and were registered (17.2%). Nearly 70% imposed restrictions on research areas, including specific disciplines (27.0%), diseases (21.3%), and interventions (14.8%), among others. The research primarily focused on exploring the impact of primary study characteristics (92.6%), while 62.3% of the studies included systematic reviews (SRs) as research samples, with 20.5% solely including Cochrane SRs. Among these, nearly 50% of the studies had sample sizes of less than 50 SRs. The most common sources for research samples were literature databases (91.0%), and 63% only searched one or two databases, with the three most frequently used being the Cochrane Library (70.3%), PubMed/MEDLINE (69.4%), and Embase (30.6%). About half of the studies (44.1%) limited the specific search time, and various limitations were applied to outcome, language, and sample size during subsequent literature screening. For 76 studies based on SRs, further restrictions were placed on the study type (23.6%), number (23.6%), and type of outcome (26.3%).
Conclusions: There was a lack of standardized sample selection criteria in the previous meta-epidemiological studies, resulting in diverse sources and types of samples. Additionally, the small sample size and various restrictions on the research samples result in insufficient representativeness. The findings derived from these studies, which were based on individually defined samples, might not be generalizable.