Overlap Matrix—Pneumonia (■ = Primary Study Included in Review)
Systematic Review	Weiner 1998 [38]		Hulzebos 2006 (Helders) [33]	Hulzebos 2006 (van Meeteren) [37]	Ferreira 2009 [36]	Carvalho 2011 [34]	Herdy 2008 [39]	Chen 2019 [35]	Stammers 2016 [40]	Valkenet 2017 [42]	Argunova 2022 [41]
Cursino de Moura 2024 [18]	■		■	■	■	■		■
Hulzebos 2012 [21]	■		■	■	■	■
Katsura 2015 [31]	■		■	■	■	■
Steinmetz 2023 [7]							■		■
Steinmetz 2026 [29]	■		■				■			■	■
Thybo Karanfil & Møller 2018 [23]	■		■	■	■	■
Wang 2024 [30]	■		■	■	■	■		■		■
Yau 2021 [5]							■		■
Frequency	6		6	5	5	5	3	2	2	2	1
Note: Frequencies represent the number of systematic reviews in which each primary study appears. Columns are ordered by frequency (highest to lowest). This matrix illustrates which primary studies were included in each systematic review reporting pneumonia (■ = included). The clustering of squares around specific studies demonstrates substantial overlap, with multiple reviews drawing on the same core set of evidence.