Objective To systematically review the effect of vitamin D (VitD) supplementation on cognitive function in people with cognitive impairment and non-cognitive disorders. MethodsThe PubMed, Web of Science, Cochrane Library, EMbase, CBM, CNKI, WanFang Data and VIP databases were searched to collect randomized controlled trials (RCTs) about the effect of VitD supplementation on cognitive function of patients with cognitive impairment or non-cognitive disorders from inception to March, 2022. Two reviewers independently screened the literature, extracted data, and assessed the risk of bias of the included studies. Meta-analysis was then performed using RevMan 5.4 software. Results A total of 19 articles including 8 684 cases were included. The results of meta-analysis showed that mini-mental state examination (MMSE) score (MD=1.70, 95%CI 1.20 to 2.21, P<0.01), Montreal cognitive assessment (MoCA) score (MD=1.51, 95%CI 1.00 to 2.02, P<0.01), Wechsler Adult Intelligence Scale-Revised (WAIS-RC) score (MD=9.12, 95%CI 7.77 to 10.47, P<0.01) and working memory (SMD=1.87, 95%CI 1.07 to 2.67, P<0.01) in the VitD group of patients with cognitive impairment were all better than those in the control group. However, the overall cognitive function and working memory of the non-cognitive impairment population were not significantly different compared with the control group. In terms of language fluency and language memory, there was no significant difference between the VitD group and the control group. In terms of the executive functions, at the intervention time of> 6 months, the VitD and control groups were statistically significant (SMD=0.15, 95%CI 0.01 to 0.28, P=0.03). Conclusion Current evidence suggests that VitD supplementation can effectively improve the overall cognitive function and working memory of patients with cognitive impairment, and has a positive effect on executive function at an intervention time of >6 months. Due to the limited quality and quantity of the included studies, more high-quality studies are needed to verify the above conclusion.
Objective To retrospectively analyze the search strategy of systematic reviews/meta-analyses(SRs/MAs) of nursing researches, and to provide the references for developing search strategy of SRs/MAs of nurse researchers in future. Methods The SRs/MAs in nursing journals from CSCD and Web of Science were searched from inception to October 2015. Four reviewers independently screened literatures and extracted data. Then data analysis was conducted by using Excel 2007 software. Results A total of 112 nursing SRs/MAs were finally included, 44 were published in English and 68 were published in Chinese. 37.5% (42/112) SRs/MAs reported the flow charts, 13.39% (15/112) reported the knowledge of reviewers, and 8.04% (9/112) reported the comprehensive search strategies. 48.21% SRs/MAs searched less than five databases, 15% SRs/MAs searched more than ten databases. 45.54% SRs/MAs reported supplementary retrieval, 8.93% searched the gray literatures. Patients combined with intervention was the most way in searching. Conclusion There are still some limitations in search strategy of SRs/MAs for nursing studies. We advise that: (1) it’s necessary to choice typical databases as many as possible according to search field; (2) the reporting of search strategy of nursing SRs/MAs should reporte knowledge of reviewers; (3) to improve transparency and quality of SRs/MAs in nursing researches, journals should introduce reporting complete search strategy in their instruction for authors.