Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Prevention of pressure ulcers
RCT	1972 acute and elective inpatients at least 55 years old admitted to vascular, orthopaedic, medical, or care-of-the-elderly wards In review	Proportion of people developing new pressure ulcers of grade 2 or above 101/982 (10%) with alternating-pressure mattresses 106/989 (11%) with alternating-pressure mattress overlays	RR 1.04 95% CI 0.81 to 1.35		Not significant