Overlap Matrix—Length of Stay (■ = Primary Study Included in Review)
Systematic Reviews	Hulzebos 2006 (Helders) [33]	Hulzebos (van Meeteren) [37]	Arthur 2000 [43]	Chen 2019 [35]	Sawatzky 2014 [50]	Sobrinho 2014 [53]	Valkenet 2017 [42]	Herdy 2008 [39]	Rosenfeldt 2011 [49]	Savci 2011 [52]	Rajendran 1998 [47]
Cursino de Moura 2024 [18]	■	■		■
Elbadrawy 2025 [27]		■	■
Gomes Neto 2017 [20]	■	■
Hulzebos 2012 [21]	■	■									■
Hurtado-Borrego 2025 [22]					■			■	■
Kendall 2018 [32]
Marmelo 2018 [4]	■	■	■		■	■	■			■
Rodrigues 2021 [24]	■	■		■		■
Shahood 2022 [26]	■	■		■		■	■			■
Snowdon 2014 [25]	■	■									■
Steinmetz 2023 [7]			■		■			■	■
Steinmetz 2026 [29]	■		■		■		■	■	■
Wang 2023 [28]	■			■		■	■			■
Wang 2024 [30]	■	■	■	■		■	■	■	■	■	■
Yau 2021 [5]			■		■
Frequency	10	9	6	5	5	5	5	4	4	4	3
Note: Frequencies represent the number of systematic reviews in which each primary study appears. Columns are ordered by frequency (highest to lowest). Due to volume of papers only those included more than twice are included. This matrix illustrates which primary studies were included in each systematic review reporting LOS (■ = included). The clustering of squares around specific studies demonstrates substantial overlap, with multiple reviews drawing on the same core set of evidence.