Study selection criteria

The search strategies described above provided a list of studies. The titles and abstracts of all the retrieved studies were screened independently by two authors. The irrelevant studies were discarded in the first attempt. The full-text version of the shortlisted studies was then analyzed for the presence of a measurable outcome variable in terms of incidence, risk ratio (RR), OR, or proportions of AF among diabetic nephropathy patients and diabetic patients without nephropathy, depending upon the study design. Also, we took care not to overestimate the measure of effect between the exposure of interest and the outcome. Therefore, we chose to include studies with a sample size of at least 100 in both groups. We did not pose any restrictions on the language of the articles as most of the articles could be translated by the google translate tool; most of the journals supported language conversion.