Methodological quality of systematic reviews on treatments for Alzheimer's disease: a cross-sectional study

Background Carefully conducted systematic reviews (SRs) can provide reliable evidence on the effectiveness of treatment strategies for Alzheimer's disease (AD). Nevertheless, the reliability of SR results can be limited by methodological flaws. This cross-sectional study aimed to examine the methodological quality of SRs on AD treatments, along with potentially relevant factors. Methods To identify eligible SRs on AD treatments, four databases including the Cochrane Database of Systematic Reviews, MEDLINE, EMBASE, and PsycINFO were searched. The Assessing the Methodological Quality of Systematic Reviews 2 instrument was used for quality appraisal of SRs. Multivariable regression analyses were used to examine factors related to methodological quality. Results A total of 102 SRs were appraised. Four (3.90%) SRs were considered as high quality; 14 (13.7%), 48 (47.1%), and 36 (35.3%) were as moderate, low, and critically low quality, respectively. The following significant methodological limitations were identified: only 22.5% of SRs registered protocols a priori, 6.9% discussed the rationales of chosen study designs, 21.6% gave a list of excluded studies with reasons, and 23.5% documented funding sources of primary studies. Cochrane SRs (adjusted odds ratio (AOR): 31.9, 95% confidence interval (CI): 3.81-266.9) and SRs of pharmacological treatments (AOR: 3.96, 95%CI: 1.27-12.3) were related to the higher overall methodological quality of SRs. Conclusion Methodological quality of SRs on AD treatments is unsatisfactory, especially among non-Cochrane SRs and SRs of non-pharmacological interventions. Improvement in the following methodological domains requires particular attention due to poor performance: registering and publishing protocols a priori, justifying study design selection, providing a list of excluded studies, and reporting funding sources of primary studies.