1. All reported adverse events.

Study ID	Results		Comment
Comparison: foam surfaces versus alternating pressure (active) air surfaces
Nixon 2019	Related and unexpected serious adverse events: 0 Expected adverse events/ serious adverse events: 167/1013 The proportion of deaths: 84/1013, 8.3% Re‐admission rates: 62/1013, 6.1% Fall rates: 159/1013, 15.7%	Related and unexpected serious adverse events: 0 Expected adverse events/ serious adverse events: 163/1017 The proportion of deaths: 82/1017, 8.1% Re‐admission rates: 82/1017, 8.1% Fall rates: 152/1017, 14.9%	Similar between groups
Rosenthal 2003	See comment	See comment	One death; but the authors did not specify which group the death was in.
Sauvage 2017	No serious adverse events (SAEs) reported Twenty adverse events, including 1 hyperalgesia	Serious adverse events: 2 deaths, a massive septic shock with acute pulmonary oedema and a decompensation of an insulin‐dependent diabetes. Twenty adverse events, including 2 discomforts.	Events other than discomfort and hyperalgesia did not involve the mattresses. It is unclear if adverse events were reported per individual participants.
Comparison: Foam surfaces versus reactive air surfaces
Allman 1987	Death: 7 Pneumonia: 4 Urinary tract infections: 7 Hypotension: 7 Hypernatraemia: 5 Oliguria: 8 Sepsis: 6 Fever: 22 Heart failure: 6	Death: 8 Pneumonia: 2 Urinary tract infections: 10 Hypotension: 6 Hypernatraemia: 5 Oliguria: 5 Sepsis: 7 Fever: 16 Heart failure: 3	Some patients appeared to have multiple adverse events.