Outcomes	Results
Comparison: Foam surfaces compared with surfaces that could not be classified
Proportion of participants developing a new pressure ulcer (follow‐up duration minimum 5 days, maximum 7 months)	Eight studies (4066 participants) that compared foam surfaces with undefined 'standard hospital surfaces' reported inconsistent results: five (3485 participants) reported no difference in the proportion of participants developing a new pressure ulcer between these surfaces (Berthe 2007; Feuchtinger 2006; Gunningberg 2000; Laurent 1998; Russell 2003a); two (168 participants) suggested foam surfaces reduced the risk of having new pressure ulcers (Hofman 1994; Park 2017); one (413 participants) suggested foam surfaces increased the risk (Schultz 1999). Van Leen 2018 (206 participants) compared foam surfaces with the Bedcare surface. The study reported that 5 of 103 (4.9%) people using foam surfaces developed a new pressure ulcer and 9 of 103 (8.7%) people using undefined reactive surfaces developed new ulcers. The RR is 0.56 (95% CI 0.19 to 1.60).
Time to pressure ulcer incidence (follow‐up duration minimum 5 days, maximum 7 months)	Three studies (3072 participants) that compared foam surfaces with undefined 'standard hospital surfaces' reported this outcome measure: Berthe 2007 (1729 participants) suggested foam surfaces reduced the hazard of developing a new ulcer whilst Feuchtinger 2006 and Russell 2003a (1343 participants) suggested no difference between foam surfaces and 'standard hospital surfaces'.
Support‐surface‐associated patient comfort (follow‐up duration minimum 11.5 days, maximum 14.0 days)	Two studies (1269 participants) that compared foam surfaces with undefined 'standard hospital surfaces' reported this outcome (Gunningberg 2000; Russell 2003a). The two studies reported different measures and outcome data: Gunningberg 2000 measured comfort using a five point scale (higher score = better comfort) and reported a mean rating of comfort of 4.2 for foam surfaces and 4.0 for standard hospital mattress. Russell 2003a measured this using a ten point scale (higher score = poorer comfort) but reported no significant differences in comfort between foam mattresses (mean 2.33 and SD 0.98) and standard hospital mattress (mean 2.46 and SD 1.0).
All reported adverse events (follow‐up duration 12 weeks)	Van Leen 2018 (206 participants) compared foam surfaces with Bedcare surfaces. The study reported this outcome but stated that there was no reported adverse events in either study group. It is uncertain if there is a difference in the adverse effects between foam surfaces and the undefined reactive surfaces. Evidence was of very low certainty, downgraded twice for high risk of bias in a domain other than performance bias, and once for imprecision as the sample size was small and the number of events was relatively low.
Cost‐effectiveness (follow‐up duration 11.5 days)	Russell 2003a (1168 participants) compared foam surfaces with undefined 'standard hospital surfaces'. The study reported this outcome using two measures: cost per any pressure ulcer (including blanching erythema) prevented; and cost per non‐blanching erythema (or worse) avoided. The results suggest that foam surfaces have a 88% probability of being cost effective compared with standard hospital surfaces in preventing any pressure ulcer (including blanching erythema); and have a 95% probability of being cost effective in preventing non‐blanching erythema or worse.