Calculate the actual overlap in an overview

The purpose of the present paper is to investigate and calculate the actual overlap of studies entered an overview using newly introduced and valid measures presented in the form of practical examples. For this purpose, an overview study entitled “effects of telemedicine on patients' quality of life with heart failure: an overview of systematic reviews” was used. Review x primary publication table was drawn by determining the number of primary reviews and studies entered the overview. The studies' degree of overlap was then calculated by the visual tool called citation matrix and indices of % overlaps, Corrected Covered Area (CCA), and Covered Area (CA). According to the results, overlaps (62.7%), CA (0.146), and CCA (0.101) were obtained. While % Overlaps is high, CCA is between 0 and 2, which is a slight overlap sign. This is because in the % overlaps calculation formula, primary studies can be counted only once, and even if they are included in several other systematic reviews, they will be calculated only once in the formula. But CCA overlap report is more accurate because, in its formula, primary studies included in one review and the repetition of these primary studies in other reviews are counted and calculated in the formula. Therefore, for investigating the overlap in overview studies, CCA calculation and report are recommended.