Commentary on “Frequency and Risk Factors of Subsyndromal Delirium in the Intensive Care Units: A Prospective Cohort Study” by Gao et al [Letter]

Dear editor

I would like to congratulate to the authors, Gao et al¹ for their scientific work titled “Frequency and Risk Factors of Subsyndromal Delirium in the Intensive Care Units: A Prospective Cohort Study” being published in this high-quality journal. I read this article with great interest and I feel it is important for the scholars to have clarification on this article regarding how a prospective cohort study design is utilized and for the improvement of the inconsistencies occurred in this article, which are very significant issues for the scientific community.

First, there are inconsistencies of the title with objective, aim, results and discussion in the document. Title: “Frequency and Risk Factors of Subsyndromal Delirium in the Intensive Care Units: A Prospective Cohort Study”, Objective: “The aim of this study was to explore the prevalence and risk factors for SSD among adult patients admitted to the ICU of XXX hospital in Southwest China”, Aim: “the aim of this study was to evaluate the incidence and risk factors of SSD in ICU patients admitted to a tertiary care hospital in southwest China, Results and Discussion: “about the prevalence and risk factors for SSD”.

Second, the prospective cohort study design is inappropriately used in this study. This is because in a cohort study design, the researcher starts with the study subjects who do not develop the outcome of interest and follow them to determine their status. Prior to observing the outcome of interest, the study subjects will be grouped depending on their exposure characteristics. Clinical trials and cohort studies are used to measure incidence and risk factors because they involve the follow-up of subjects over time.² “Cohort study design is used to compare the group of subjects who are exposed to a certain risk factor with a comparison group who are not exposed”.³ Besides, the authors did not use the “Strengthening the Reporting of Observational studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies” for the reported study design.⁴

Third, this article has addressed the prevalence and associated factors with SSD by using cross-sectional study design. This is evidenced by; clinical trials and cohort studies are used to measure incidence and risk factors because they involve the follow-up of subjects over time. Whereas, cross-sectional studies and case-control studies (that use prevalent rather than incident cases) are used to measure the prevalence.² Generally, a cross-sectional study design is used to assess the selected population at a given period of time and permits to describe the associations between several factors and determine their prevalence.^5–7

In conclusion, I need to ask the authors to explain their decision-making about the reported prospective cohort study design and the measure of SSD prevalence versus SSD incidence and associated factors versus risk factors. Lastly, I would like to suggest the authors to use the STROBE reporting guidelines in their future reporting of observational studies.