Searching technique
This study is a meta-analysis, based on the findings of studies on the prevalence of severe depression among Iranian older adult, including articles published in domestic and foreign journals and searches carried out in the databases of Sciencedirect, Scopus, SID, magiran, Medline (PubMed), Barakat Knowledge Network System, and Google Scholar between January 2000 to August 2019. The search process was carried out using the keywords Older adult, Depression, Mood Disorders, Types of Depression, Severe Depression and their English equivalents and their possible combinations, so that the process of the Persian databases were searched using the mentioned Persian keywords and in the English databases using their English equivalents including Older adult, Depression, Mood disorders, Types of depression, Severe depression as well as in the Google Scholar search engine using both English and Persian words. AND and OR operators were used in combination to provide more comprehensive access to all articles, therefore, the OR operator was used to check for common names for disorders such as (Older adult OR Aging), (depression OR Depressive Disorder), (mood disorders OR Affective Disorders). The AND operator was also used among the keywords (Older adult AND depression AND severe depression) by matching words in the MeSH browser.
((((((Older adult [Title/Abstract]) OR Aging [Title/Abstract]) AND depression [Title/Abstract]) OR OR Depressive Disorder [Title/Abstract]) OR severe depression [Title/Abstract]) AND mood disorders [Title/Abstract]) OR Affective Disorders [Title/Abstract]))))).
Criteria for selection and evaluation of articles
All articles were first collected using the selected keywords and a list of abstracts was prepared after the search was completed. After hiding the article specifications, including the name of the magazine and the author, the full text of the articles was made available to the reviewers. Each article was studied independently by two reviewers and if the article was excluded, the reason was mentioned. Moreover, if there were differences between the two reviewers, the article was judged by the third reviewer and the third reviewer’s opinion was considered. Articles in Persian and English extracted from cross-sectional studies on the prevalence and of severe depression in Iranian older adult met the inclusion criteria. Other review, case-control, cohort, and intervention studies were excluded from the list of articles. To review gray literature, i.e. that piece of evidence and documents that have not been published for any reason, attempts to search the Google search engine search and related websites were also on our agenda. The studies were then reviewed based on four-phase PRISMA (2009), including identifying articles, screening, reviewing articles acceptance criteria, and finally articles entered the meta-analysis.
Quality control
STROBE checklist was used to review studies. This checklist consists of 22 sections, 18 of which are general and applicable to all observational studies, including cohort, case-control, and cross-sectional, and 4 are specific depending on the type of study and include various methodological aspects, including study objectives, determination of appropriate sample size, type of study, sampling method, research population, data collection method, definition of variables and procedure, study data collection tool, study objectives, statistical tests, and findings. Accordingly, a maximum quality evaluation score of 32 was considered and articles with scores below 14 were recognized poor in terms of quality evaluation and were excluded from the study.
Statistical analysis
In each study, the prevalence of severe depression in the older adult was obtained in studies in Iran. The heterogeneity of the studies was assessed using the I2 test. In general, heterogeneity was classified into three categories, heterogeneity less than 25% (low heterogeneity), Between 25 and 75% (moderate heterogeneity) and 75% (high heterogeneity), data were analyzed using Comprehensive Meta-analysis software (Biostat, Englewood, NJ, USA version 3), probability of publication bias Funnel chart using Egger test and significance level 0.05 and also to investigate the effects of potential factors on heterogeneity of studies from Meta-regression test in two groups. Mel sample size of the study were used.