Study registration
This SR protocol have been priori registered on PROSPERO at 30 April 2020 (registration ID: CRD42020182979). Our protocol is reported in according to the Preferred Reporting Item for Systematic Review and Meta-analysis-Protocol (PRISMA-P) statement (Additional file 1) and referred to the MOOSE guidelines for Meta-Analyses and Systematic Reviews of Observational Studies[31]. The results of this SR will be reported according to the PRISMA statement and MOOSE guidelines.
Inclusion criteria
We will include studies based on the following criteria:
Studies characteristics
- Population-based, cross-sectional surveys investigated the Chinese prevalence of depression in patients with T2DM or/and researched the possible risk factors associated with development of depressive symptoms, regardless of sample size;
- Studies published in English or Chinese.
Participant characteristics
- Chinese adults (≥ 18-year-old) diagnosed with T2DM based on self-reported physician’s diagnosis, medical records or glucose level testing (fasting plasma glucose ≥ 7.0 mmol/L and/or 2 hours plasma glucose ≥ 11.1 mmol/L)[32];
- T2DM patients were defined as depression by screening instruments which have been verified to have good validity and reliability in Chinese population (eg. Patient Health Questionnaire-9, Hamilton Depression Scale, Self-rating Depression Scale, Center for Epidemiologic Studies Depression Scale, Beck depression inventory, Composite International Diagnostic Interview, the Geriatric depression)[33];
3) No restrictions on gender and geographical region.
Type of outcome measurements
- Our primary outcome will be the pooled Chinese prevalence of depression in T2DM patients;
- The secondary outcome will contain the potential risk factors for depression in patients with T2DM in China, such as gender, age, educational level, complications and living habit (eg. smoking, drinking history and exercise habit).
Exclusion criteria
We will exclude studies meeting one of the following criteria:
1) Hospital-based studies;
2) Randomized trials, case studies, qualitative studies, systematic reviews, protocols, commentaries, editorials and conference abstracts;
3) Full text can’t be obtained or data that can’t be extracted;
4) Repeated publications (we will include study with the most complete data).
Databases and search strategy
Electronic databases including MEDLINE/PubMed, EMBASE, the Cochrane Library, Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Periodical Database (VIP), and Wanfang database will be searched. Both Medical Subject Headings (MeSH) and free text words related to China, diabetes and depression will be used for searching relevant articles. The search strategy of PubMed was shown in Additional file 2. Suitable strategies will be applied in other electronic database in accordance with respective retrieval rules. We will search reference lists of included articles and relevant SRs for additional eligible studies. Grey literature will also be manually searched such as conference proceedings and academic degree dissertations.
Study selection
We will use reference management software (ENDNOTE X9) to manage the all articles collected from literature search. After filtering out the duplicate records, two independent reviewers (HLZ and JZ) will screen the titles and abstracts of the rest records to acquire potentially eligible studies preliminary. Then, full texts will be obtained and checked independently by two reviewers (XBL and JF) to identify the eligible studies. All screening processes will be based on inclusion and exclusion criteria. Any disagreements will be discussed with a third reviewer (JL) to meet a consensus. We will provide a list of excluded studies and justify the exclusions. PRISMA flow diagram will be presented to describe the screening and selection processes.
Data extraction
Once eligible studies are identified, two reviewers (YXL and DLZ) will independently extract the data using a prepared data extraction form. The extracted data from each study will include:
- Study characteristics: title, journal, conducted year(s), country, geographical region, method of data collection, criteria used to define diabetes and depression, source of funding;
- Participants information: mean age, gender, history of diabetes, education level, living habit (eg. smoking, drinking history and exercise habit), diabetes treatment (eg. diet control, oral medicine, use of insulin), and other relevant reported demographic, health, and diabetes-related information;
- Critical data: sample size, the number of subjects with depression, response rate, the reason for non-response, potential risk factors associated with development of depression in T2DM with their respective subjects’ number and/ or respective odds ratio (OR) and 95% confidence interval (CI).
If necessary, we will contact the corresponding authors by e-mail for any incomplete information and data. Finally, the extracted data will be cross-checked, a third reviewer (JRJ) will participate in discussion if there are any disagreements.
Quality assessment
Two reviewers (LG and CD) will assess the quality of included studies dependently by the Agency for Healthcare Research and Quality (ARHQ) methodology checklist which is devised for cross-sectional/prevalence study quality[34, 35]. ARHQ methodology checklist consists of 11 items, and each item will be answered with “Yes”, “No” or “Unclear”. An item will be scored “1” if answered with “Yes” and scored “0” if answered with “Unclear” or “No”. A study will be defined as high-quality if the total scores greater than 7 points. Assessment results will be cross-checked, and disagreement will be determined by a third reviewer (JL).
Data analysis
We will calculate the primary outcome of prevalence with 95% CI of depression in T2DM patients by pooling the proportion of T2DM with depression in each included study. Meanwhile, to explore potential risk factors, we will calculate the OR values and 95% CI of the reported risk factors for depression in T2DM patients, and it will be considered statistically significant when OR value and 95% CI is not equal to 1 and P <0.05[36]. The statistical heterogeneity among studies will be assessed by the Cochran's Q test and the I2 statistic. P value < 0.10 for the Q test and an I² > 50% will be set as the threshold for statistically significant heterogeneity. Since heterogeneity is expected, we will use random-effects model to pool all outcomes. We will assess inter-rater agreement between reviewers for study inclusion, data extraction, and study quality assessment using Kappa statistics. Strength of agreement will be divided into 6 categories according to Kappa statistics: poor (< 0.00), slight (0.00-0.20), fair (0.21-0.40), moderate (0.41-0.60), substantial (0.61-0.80), or almost perfect (0.81-1.00)[37]. All statistical analyses will be performed using R software (vision 3.6.1) and STATA (vision 12.0) software.
Subgroup analysis
In the subgroup analyses, we will obtain respective prevalence of depression in T2DM patients according to the characteristics which are consistent with potential risk factors, such as gender, age, educational level, complications and living habit (eg. smoking, drinking history and exercise habit) and other characteristics (based on authors’ report). In addition, subgroup analyses based on different ways of defining depression (eg. Patient Health Questionnaire-9, Hamilton Depression Scale, or Self-rating depression scale) and quality of included studies (score > 7 and score ≤ 7) will be carried out.
Meta-regression analysis
If there are statistically significant heterogeneity, meta-regression analysis will be used to investigate the potential sources of heterogeneity. Based on available data points and number of included studies, we plan to conduct meta-regression analyses by type of depression screening instruments, age (average age), gender (proportion of women), year of study conduct and so on.
Publication bias
If there are ≥ 10 studies in primary outcome and in each potential risk factors, we will use Funnel plots and Egger’s test to assess publication bias.