There are two possible ways to conceptualize the term “insomnia”: insomnia disorder and insomnia symptoms, which are often poorly reported. The purpose of this study was to examine the proportion of randomized controlled trials (RCTs) and systematic reviews (SRs) that mention insomnia in their abstracts and cannot distinguish between insomnia disorder and insomnia symptoms from the abstract. We included RCT and SR articles that included the word “insomnia” in the methods or results sections of their structured abstracts, published after 2010. We searched PubMed using English language restrictions on 10 March 2022. From 1580 PubMed articles, we obtained 100 random samples each for eligible RCTs and SRs. The unclear insomnia concept accounted for 88% of the RCT abstracts and 94% of the SR abstracts. Among the RCT and SR abstracts with unclearness, the concept of insomnia was unclear in 27% of RCTs and 57% of SRs after investigating the full text. The concept of insomnia has been unclear in many RCTs and SRs abstracts. The authors of RCTs and SRs are recommended to state “insomnia disorder” or “insomnia symptoms” in the methods and results sections of their abstracts.

Objectives. To examine tendencies and characteristics of randomized controlled trials (RCTs) and systematic reviews (SRs) that mention insomnia in abstracts and cannot be distinguished between insomnia disorder and insomnia symptoms (insomnia types) from the abstract and what is the intent of the unclear insomnia types described in the abstracts. Methods. This study is a meta-epidemiological study. We will include RCT and SR articles that include the word “insomnia” in methods or results of structured abstracts, published after 2010. We will exclude RCTs and SRs, which had neither methods nor results in non-structured abstracts. We will search MEDLINE via PubMed with English language restrictions. We will extract the information about whether abstracts of RCTs and SRs describe insomnia type clearly or not, and the characteristics. We will also extract information about the diagnosis of insomnia disorder for RCT and SR articles with unclear insomnia types and which intent insomnia disorder as insomnia in abstracts. We will report the proportion of RCT and SR articles with unclear insomnia types. We will compare characteristics between RCT and SR articles with unclear insomnia types and those with clear insomnia types. We will examine the above possible characteristics associated with the unclear insomnia types using multivariable logistic regression. We will report what was the intent of the unclear insomnia types described in the abstracts. We will also report what and how much proportion of diagnostic criteria was used for insomnia disorder for RCT and SR articles with unclear insomnia types. Ethics & Dissemination. This study does not need ethical approval. We registered this study protocol. We will publish the findings in a peer-reviewed journal and may present them at conferences. Discussion. This study will clarify what proportions and characteristics that do not describe insomnia type clearly in abstracts of RCTs and SRs. The results will inform the researchers, reviewers, and readers of the points that need special attention. Registration: Protocols.io