. 2015 Aug;41(5):907–924. doi: 10.1016/j.burns.2014.11.002

Table 3.

Characteristics of primary studies included in the review.

First author	Design and risk of bias^a	Participants	Content of intervention	Scald injuries/Preventive measures N (%), Effect size (95%CI)
Babul [49]	RCT A–Y B–N F–N	Parents of new born infants at a general hospital serving mainly urban or suburban communities N = 600	I₁: home visit from community health nurse, home safety check to identify hazards and teach parents how to remove or modify the hazards; free safety kit (smoke alarm, safety gate 50% discount coupon, table corner cushions, cabinet locks, blind cord windups, water temperature card, doorstoppers, electrical outlet covers, poison control sticker); instructional brochure targeting falls, burns, poisoning and choking; risk assessment checklist. I₂: free safety kit (see I1). C: usual care.	Hot water temperature Safe hot water temperature (not defined) I₁ = 121 (70%) I₂ = 113 (69%) C = 80 (54%) I₁ vs C OR = 2.65 (1.57, 4.46) I₂ vs C OR = 2.21 (1.32, 3.69) Using temperature card I₁ = 135 (78%) I₂ = 104 (63%) OR = 2.38 (1.42, 3.97) Hot drinks and food safety Keeping hot drinks or food out of reach of children I = 325 (97%) C = 147 (99%) OR = 0.44 (0.10, 2.04)
Barone [50]	RCT A–N B–N F–N	Couples or individuals participating in well-child parenting classes N = 79	I: slides, handouts on burn prevention, bath water thermometer, hot water gauge, and usual safety education C: usual safety education	Hot water temperature Safe hot water temperature (not defined) I = 16 (40%) C = 15 (39%) OR = 1.02 (0.41, 2.53)
Carlsson [62]	NRCT B–U F–N C–N Intervention group had higher rate of child injuries than control group at baseline	Mothers with low educational level with 4–7-month-old babies attending two child health care centres N = 99	I: 30–60 min workshop discussing burn and scald prevention and a 1 h home visit offering individual-based information focusing on problem described by mothers and solutions and suitable actions to take regarding child injury prevention in the home C: usual care	Hot drinks and food safety Electrical cords or iron or coffee and water heating appliances not within reach of children I = 37 (95%) C = 23 (74%) OR = 4.8 (0.5, 49.2) Kitchen and cooking safety Cooker child protected I = 25 (64%) C = 10 (32%) OR = 3.08 (1.1, 8.7) Cooker securely anchored I = 21 (54%) C = 9 (29%) OR = 2.3 (0.8, 6.6) Cooker door secured I = 24 (62%) C = 16 (52%) OR = 1.2 (0.4, 3.3) Climbing possibilities to sink removed I = 30 (77%) C = 12 (39%) OR = 4.4 95%CI 1.5, 13.1
Chow [60]	RCT A–Y B–U F–N	Families in two districts of Hong Kong with children under 3 years admitted to hospital with an unintentional injury N = 170	I: educational materials, 4 quarterly home visits with active guidance on injury prevention and regular monthly telephone follow-ups with no scheduled visits from trained home visitors C: educational materials on injury prevention, and 2 assessment only visits	Hot drinks and food safety Significantly more intervention group families tested temperature of micro-waved food. p = 0.05 Figures not reported Kitchen and cooking safetySignificantly more intervention group families using child-proofed boilers and rice cookers and electrical heating devices. p = 0.05. Figures not reported p Values come from Chan [71] and Cooper et al. [70]
Christakis [31]	RCT A–Y B–Y F–Y	Parents of children < 11 years attending clinics in the previous 3 years N = 887	I₁: web-based safety information for parents plus health care provider notification of safety topics parents had expressed interest in on-line and information I₂: health care provider notification I₃: web-based safety information for parents C: usual	Hot water temperature Hot water temperature < 51.6 °C I₁ = 23 (13%), I₂ = 24 (13%), I₃ = 25 (12%), C = 14 (7%). No p value reported
Colver [64]	RCT A–U B–U F–N	Families with children < 5 years attending child health clinics, day nurseries, nursery classes and a toddler group in deprived area (n = 80)	I: encouraged to watch TV safety campaign; home visit; advice on benefits to obtain safety equipment and local availability of safety equipment. C: encouraged to watch TV safety campaign	Kitchen and cooking safety In group I, 7 family had cooker guards obtained and fitted No p value reported Other scald outcomesMade home safer I = 22 (60%) C = 4 (9%)
Gaffney [51] Abstract only available	CBA B–U F–U C–U	Populations of unspecified control and intervention areas (N not reported)	I: multi-faceted community campaign to reduce risk factors and the rate of hot water scalds in children aged 0–4 years C: no campaign	Other scald outcomes No changes in use of scald limiting products and preventive behaviours (undefined). No figures or P values reported
Georgieff [39]	CBA B–U F–N C–N Intervention group had higher percentage of single parents than control group at baseline	Children < 3 years from 5 deprived wards N =92	I₁: awareness raising campaign including leaflets, a logo, a radio advert campaign, a bus advertising campaign, burns and scalds road shows (advice): free bath water thermometers (engineering) and hot tap water temperature testing by researchers I₂: advice only C: no intervention	Hot water temperature Mean temperature after intervention (°C) I₁ = 26, I₂ = 31, C = 35. Hot water outlet temperature > 49 °C I₁ = 12 (46%), I₂ = 19 (61%), C = 26 (74%) Hot water temperature ≤ 49 °C I₁ = 3 (12%), I₂ = 5 (16%), C = 5 (14%) Unsure if hot water outlet temperature is ≤ 49 °C I₁ = 11 (42%), I₂ = 7 (23%), C = 4 (11%) Checks water temperature with elbow or thermometer I₁ = 19 (73%), I₂ = 16 (52%), C = 15 (43%) Ever put child into bath without checking water temperature I₁ = 0 (0%), I₂ = 0 (0%), C = 2 (6%) Owns TMV's I₁ = 6 (29%), I₂ = 0 (0%), C = 0 (0%) Uses thermostatic adjustment to reduce water temperature I₁ = 5 (23%), I₂ = 2 (6%), C = 2 (6%) Has left a run bath unattended I₁ = 9 (35%), I₂ = 7 (23%), C = 16 (46%) Uses tap cover or sits child away from tap I₁ = 1 (4%), I₂ = 1 (3%), C = 4 (11%) Does not put child in bath while bath running I₁ = 5 (19%), I₂ = 3 (10%), C = 4 (11%) Adult runs the bath I₁ = 25 (96%), I₂ = 25 (81%), C = 31 (89%) Child bathes with supervision I₁ = 17 (65%), I₂ = 13 (41%), C = 18 (51%) No p values reported for any outcomes
Gielen [35]	RCT A–U B–U F–U	First and second year paediatric residents and their patient-parents, low income population of parents of children aged 0–6 months (n = 187).	I: safety counselling by professional health educator; discounted home safety equipment during visit to Children's Safety Centre; home visit involving hazard assessment (targeting falls, burns and poisonings) and safety recommendations. C: safety counselling by professional health educator; discounted home safety equipment during visit to Children's Safety Centre	Hot water temperature Hot water temperature ≤ 48.9 °C I = 27 (47%), C = 27 (47%), no significant difference between groups. No p value reported
Gomez-Tromp [63]	CBA B–U F–U C–U	Children aged 9 to 13 years in 35 schools N = 1260	I: scalds prevention program consisted of seven lessons, a DVD, a workbook for each pupil and a downloadable teacher's manual C: waiting list	Hot drinks and food safety Children carrying hot water No significant difference between groups. No figures or p value reported
Hendrickson [61]	RCT A–N B–N F–Y	Mothers with children aged 1–4 years, predominantly Mexican/Mexican American N = 82	I: safety counselling from researchers; identification of home hazards; provision of safety equipment (door knob covers, smoke detectors or new batteries if smoke alarm already in situ, fire extinguisher, cabinet latches and outlet covers). C: none of the above	Hot drinks and food safety Keeping hot drinks or food out of reach of children I = 37 (97%), C = 36 (90%) OR = 4.11 (0.44, 38.57)
Katcher [45]	RCT A–U B–U F–N	Consecutive paediatric clinic clients randomised to two groups N = 697	I: counselling by paediatrician plus tap water thermometer and tap water safety literature C: counselling and tap water safety literature	Hot water temperature Hot water temperature < 54.4 °C I = 76 (76%) C = 28 (90%) OR = 0.34 (0.09, 1.22) Tested hot water temperature I = 122 (46%) C = 55 (23%) OR = 2.89 (1.97, 4.26) Boiler thermostat lowering I = 29 (14%), C = 17 (9%) No significant difference between groups. p Value not reported
Kelly [42]	RCT A–U B–Y F–N	Parents of 6 month old children attending primary care centre for well child care (n = 129)	I: three-part individualised safety course at well child care visits. C: routine safety education	Hot water temperature Hot water temperature < 52 °C I = 41 (75%) C = 34 (63%) OR = 1.72 (0.76, 3.91)
Kendrick [46]	NRCT B–N F–N C–Y	Children 3–12 months registered at 36 GP practices (n = 2119)	I: health visitor safety advice at child health surveillance; low cost equipment (stair gates, fire guards, cupboard and drawer locks, smoke alarms); home safety checks; first aid training. C: usual care	Hot water temperature Hot tap water temperature < 54 °C I = 103 (29%) C = 88 (25%) OR = 1.26 (0.90, 1.76) Hot drinks and food safety keeping hot drinks or food out of reach of children I = 191 (60%) C = 201 (63%) OR = 0.89 (0.65, 1.22)
Kendrick [24] (Risk Watch)	RCT A–Y B–N F–Y	Children aged 7–10 years in state funded primary schools N = 459	I: teachers trained by Fire Service Personnel to deliver teaching on falls; poisoning; and ﬁre and burns. Fire Service personnel provided free teaching resources. C: usual care	Kitchen and cooking safety Child never cooks without adult present I = 117 (72%) C = 141 (77%) OR = 0.90 (0.45, 1.82)
Kendrick [34]	RCT A–Y B–Y F–Y	Households with children < 5 years in social housing in disadvantaged communities N = 124	I: thermostatic mixer valve ﬁtted by qualified plumber and educational leaflets prior to and at the time of fitting C: usual care	Hot water temperature Bath hot tap water ≤ 46 °C I = 13 (81%) C = 2 (13%) RR = 6.09 (1.64, 22.62) Runs bath using cold water first I = 5 (13%) C = 11 (28%) RR = 0.55 (0.22, 1.39) Checks bath water temperature for every bath I = 32 (84%) C = 40 (100%) RR = 0.84 (0.73, 0.97) Baths are only run by adult I = 38 (95%) C = 38 (95%) RR = 1.00 (0.90, 1.10) Child baths always supervised by adult I = 32 (82%) C = 34 (85%) OR = 0.97 (0.79, 1.17) Child usually gets in bath after water has been run I = 39 (97%) C = 39 (97%) RR = 1.00 (0.90, 1.10) Child has been left alone in the bath I = 13 (33%) C = 8 (21%) RR = 1.11 (0.51, 2.41) Child has been left alone in bathroom while bath is running I = 12 (31%) C = 9 (23%) RR = 1.28 (0.62, 2.68)
King [44]	RCT A–Y B–Y F–Y	Children <8 years attending A&E for injury or medical complaint N = 1172	I: home safety check; information on correcting any deficiencies; discount vouchers for safety equipment; demonstrations of use of safety devices; information on preventing specific injuries provided by researcher. C: home safety check and safety pamphlet	Hot water temperature Hot tap water temperature ≤ 54 °C I = 257 (53%) C = 218 (46%) OR = 1.31 (1.14, 1.50)
LeBlanc [32]	Case-control NOS score = 7	Children aged ≤ 7 years presenting to an emergency department with injuries from falls, burns or scalds, ingestions or choking matched to children who presented during the same period with acute non-injury-related conditions. N = 692	Exposures of interest: tap water temperature higher than 54 °C, kettle or appliances with dangling cords, no stove guard	Exposures of interest Hot water temperature Tap water temperature >54 °C Cases = 140 (41%), controls = 154 (46%) OR = 0.85 (0.62, 1.15) Kitchen and cooking safety No stove guard Cases = 340 (99%) controls = 339 (98%) OR = 1.20 (0.37, 3.93) Kettle or appliances with dangling cords Cases = 9 (4%), controls = 14 (6%) OR = 0.64 (0.28, 1.49)
Macarthur [52]	Cohort NOS score = 6	Parents or guardians of children under 9 years N = 504	Exposed group: campaign (media, retail, and community partners) emphasising lowering hot water tap temperature, child safety in the kitchen, keeping hot drinks away from child) checking smoke alarms regularly. Unexposed group: none of the above	Hot water temperature Tested water temperature Exposed = 27 (12%), unexposed = 14 (6%) RR = 1.95 (1.05, 3.61) Lowered water temperature Exposed = 13 (6%), unexposed = 4 (2%) RR = 3.28 (1.09, 9.90) Hot drinks and food safety Let food cool before serving to children Exposed = 186 (74%), unexposed = 195 (77%) RR = 0.96 (0.87, 1.06) Kitchen and cooking safety Keeps children out of kitchen when cooking Exposed = 135 (54%), unexposed = 135 (54%) RR = 1.01 (0.86, 1.19) Cooks on back burners at stove Exposed = 102 (41%), unexposed = 119 (47%) RR = 0.86 (0.71, 1.05) Turns pot handles to the back of the stove Exposed = 21 (84%), unexposed = 214 (85%) RR = 0.99 (0.92, 1.07) Ensured electrical cords are not dangling from counter Exposed = 203 (81%), unexposed = 220 (87%) RR = 0.93 (0.86, 1.01)
Margolis [33]	Cohort NOS score =7	Low-income pregnant mothers and their infants under 2 years old in Durham, North Carolina N = 317	Exposed group: 2 to 4 home safety checks per month through the infant's first year of life providing parental education on child health and development and injury prevention Unexposed group: usual care (women who had sought prenatal care during the 9 months before the program's initiation)	Hot water temperature Hot water temperature < 49 °C Exposed group = 22 (42%), unexposed group = 10 (26%) OR = 2.1 (0.83, 5.09)
Minkovitz^*[53]	RCT A–N B–Y F–N CBA B–N F–Y C–N Control group had fewer older mothers, fewer white families, fewer years of education, more single parents, lower income and less likely to own home than intervention group at baseline	RCT Children ≤ 3 years old N = 2235 CBA Children ≤ 3 years old N = 3330	I: “Healthy Steps Programme”, which included child safety, for the first 3 years of life including extended well child office visits (average 11 in first 2.5 years of life), home visits (average <2 in first 2.5 years of life), telephone help-line, parent groups, written information. Programme delivered by paediatricians and Healthy Steps Specialists (nurses, nurse practitioners, social workers and early childhood educators). C: conventional paediatric care	RCT: Hot water temperature Lowered temperature on water heater I = 519 (64.4%), C = 441 (60.4%), p = 0.11 CBA: Hot water temperature Lowered temperature on water heater I = 645 (54.25%), C = 516 (56.3%), p = 0.82
Mock [54]	CBA B–N F–N C–N Intervention group had higher percentage of safe responses than control group at baseline	Parents in different socioeconomic strata (SES) in the city of Mexico N = 1124	I: the upper SES group received clinic-based lectures and demonstrations on motor car and pedestrian safety, burn prevention, home safety and recreational safety. I₂: the middle SES group received the intervention the same as I₁, however, some of them received clinic-based counselling. I₃:The lower SES group received injury prevention counselling at half-hour household visits C: usual care	Hot water temperature Tested hot water temperature I₁ = 0 (0%), I₂ = 0 (0%), I₃ = 1 (4%), C₁ = 2 (7%), C₂ = 0 (0%), C₃ = 0 (0%); only within group pre-post comparison p values reported
Nansel [40]	RCT A–Y B–U F–Y	Parents of children aged 6–20 months attending well child check N = 213	I: tailored computer generated safety advice in well child clinic. C: generic computer generated safety advice in well child clinic	Hot water temperature Hot tap water temperature ≤ 49 °C I = 25 (29%), C = 27 (30%) OR = 0.96 (0.50, 1.83) Hot drinks and food safety Keeping hot drinks or food out of reach of children I = 78 (92%), C = 84 (94%) OR = 0.66 (0.20, 2.18)
Nansel [41]	NRCT Participants randomly allocated to I₁ and C arms and remainder allocated to I₂ B–N F–N C–N I₂ group were older, more likely to be Caucasian and had lower educational level than control group at baseline	Parents of children aged ≤ 4 years attending well child visits at 3 paediatric clinics with mainly low to middle income patients N = 594	I₁: tailored injury prevention education I₂: tailored injury prevention education and feedback to health care provider. C: general education	Hot water temperature Safe hot tap water temperature (≤ 49 °C) I = 42 (20%) C = 26 (27%) OR = 0.71 (0.40, 1.24) Hot drinks and food safety Keeps hot drinks or food out of reach of children I = 125 (95%) C = 55 (89%) OR = 2.65 (0.85, 8.25) Kitchen and cooking safety Turns pan handles away from edge of stove I₁ = 7 (100%), I₂ = 11 (92%), C = 12 (86%) OR combining both I arms: 3.00 (0.14 to 186.62) Keeps child away from stove or oven I₁ = 4 (57%), I₂ = 10 (83%), C = 11 (85%) OR combining both I arms: 0.51 (0.04 to 3.98)
Paul 1994	RCT A–U B–U F–N	Families with children aged 10 months to 2 years born at local rural hospital N = 205	I: home safety check; tailored education booklet; local safety equipment retail outlets identified, mail order addresses provided or equipment ordered through research team and made available at local hospital. C: none of the above	Hot water temperature TMVs kitchen/bathroom/laundry: no significant difference between intervention and control groups. No figures or p value reported Hot water outlets with safety taps in kitchen/bathroom/laundry: no significant difference between intervention and control groups. No figures or p value reported
Phelan [37]	RCT A–Y B–N F–Y	Pregnant women, aged 18 years and over, < 19 weeks gestation, attending prenatal practices N =355	I: home safety check; provision and fitting of free safety equipment (stair gates, non-slip matting under rugs, window guards, repair of stair handrails, cupboard/drawer locks, door knob covers, storage bins, socket covers, smoke detectors, CO detectors, stove guards, stove locks); safety advice handout. C: safety advice handout	Hot water temperature Hot tap water temperature ≤ 49 °C I = 109 (75%) C = 94 (64%) OR = 1.69 (1.03, 2.79)
Posner [56]	RCT A–Y B–Y F–N	Caregivers of children <5 years attending ED for home injury N = 136	I: home safety counselling by trained lay personnel; home safety kit (cupboard and drawer locks, socket covers, bath tub spout covers, non-slip bath decals, bath water thermometer, poison control centre number stickers, free small parts tester); home safety literature. C: home safety literature	Hot water temperature Use of water thermometer I = 43 (88%) C = 13 (28%) OR = 18.74 (6.45, 54.47) Has spout covers for bath taps I = 39 (80%) C = 18 (38%) OR = 6.28 (2.53, 15.61) Hot drinks and food safety Keeps hot drinks or food out of reach of children I = 34 (73.9%), C = 38 (80.6%) OR = 0.67 (0.25, 1.79) Kitchen and cooking safety Cooks on back burners of cooker I = 25/49 (%)C = 16/47 (%) OR = 2.02 (0.89, 4.60) Turns pan handles towards back of cooker I = 29 (57%) C = 23 (49%) OR = 1.59 (0.71, 3.59) Other scalds outcomes Burns safety score, Mean (SD) I = 76.0 (14.9), C = 68.4 (17.4), p < 0.03
Reich [38]	RCT A–Y B–Y F–Y	Low-income primiparous women N = 198	I₁: educational intervention book during 3rd trimester and additional books when baby was 2, 4, 6. 9, and 12 months old via a home visit I₂: books with the same illustrations but with different non-educational text on the same schedule as I₁. C: did not receive any books	Hot water temperature Hot water temperature < 49 °C I vs C₁ OR = 1.07 (SE 0.31), p = non-significant I vs C₂ OR = 1.44 (SE 0.44), p = non-signifiant
Sangvai [36]	RCT A–Y B–Y F–N	Caregivers of children aged 0 to 5 years from 3 paediatric clinics at a health maintenance visit N = 319	I: safety counselling from physician and researcher, free safety equipment (smoke detectors, gun locks, cabinet locks, and water temperature cards) and brief educational hand-out for parents C: usual care	Hot water temperature Hot water temperature < 49 °C I = 6 (67%) C = 6 (86%) OR = 0.33 (0.03, 4.19)
Schwarz [43]	CBA (C) Allocation at census tract level A–U B–N F–N C–Y	Population of 9 census tracts, predominantly low income, urban, African-American I = 902 C = 1060	I: home safety check and modification; education in homes and at block and community meetings; provision of ipecac, smoke alarms and batteries, bath water thermometers, night lights, emergency centre number sticker and fridge sticker with information on preventing injury C: none of the above	Safety water temperature Hot water temperature <52 °C I = 570 (63.2), C = 776 (73.2), OR = 0.57 (0.46, 0.71)
Shapiro [58]	RCT A–U B–U F–Y	Women admitted to the maternity ward of 3 hospitals N = 604	I: Pamphlet about tap water scalds and thermometer for testing, plus a 1 min educational message summarising pamphlet C: pamphlet and thermometer	Hot water temperature Tested hot water temperature I = 155 (51%) C = 88 (29%) OR = 2.56 (1.83, 3.59) Lowered hot water temperature. Figures and p value not reported
Swart [66]	RCT A–N B–Y F–Y	Households with children under 10 years in low income communities N = 410	I: four times home safety checks plus advice on prevention of burns poisoning and falls; free safety devices (child proof locks and paraffin container safety caps). C: none of the above	Other scalds outcomes Burn hazard safety practice score Mean (SD) I = 2.5 (0.12) C = 2.9 (0.12), p = 0.021, Mean difference (95%CI) = −0.41 (−0.76, −0.07)
Sznajder [57]	RCT A–Y B–N F–Y	Socio-economically disadvantaged families when children aged 6–9 months, with medical or psychological difficulties which place them at high risk N = 100	I: free home safety kit (cupboard and drawer locks, door handle covers, furniture corner protectors, socket covers, non-slip bath mat, smoke alarm, poison control centre number stickers); home safety counselling by health professionals; safety leaflets. C: home safety counselling by health professionals; safety leaflets	Hot water temperature Hot water system has adjustable thermostat I = 5 (11%), C = 5 (10%) OR = 1.07 (0.29, 3.97) Safe hot tap water temperature (not defined) I = 0 (0%), C = 3 (6%), p value not reported
Thomas [47]	RCT A–N B–U F–Y	Parents attending well-baby classes N = 58	I: standard information and literature plus a lecture on burn prevention provided by nurse practitioners, leaflet on protecting home against fire, adjusting hot water settings and cost of smoke alarms at local stores, plus $7 discount coupon for a smoke alarm. C: standard information and literature	Hot water temperature Safe hot water temperature <54.4 °C I = 22 (76%) C = 6 (23%) OR = 10.48 (3.01, 36.47)
Waller [48]	RCT A–U B–U F–Y	A random sample of Dunedin area children ≤ 3 years taken from birth records N = 121	I: free plumbing advice, home visit to measure tap water temperature, discuss dangers of hot water in the home and how to reduce tap water temperature provided by nurses C₁: no home visit C₂: no home visit and no baseline data collection	Hot water temperature Hot water temperature < 60 °C I = 21 (41%) C = 31 (32%) OR = 1.49 (0.74, 3.01)
Williams [59]	RCT A–U B–N F–U	Pregnant women attending prenatal classes N = 74	I: 1 h lecture, handouts on burn prevention, usual safety education. C: usual safety education	Hot water temperature Safe hot water temperature (not defined) I = 22 (56%) C = 11 (31%) OR = 2.88 (1.10, 7.55)
Ytterstad [29]	CBA B–U F–Y C–N Control city had higher injury rates and educational level than intervention city at baseline	Children ≤ 5 years in the city of Harstad (intervention) and Trondheim (control) N = 14573 person years	I: promotion of tap water thermostat setting to 55 °C and of increased parental vigilance in putative burn risk situations C: none of the above	Scald injuries I = 42 (0.25%), C = 700 (0.73%). No p value reported Thermal injury severity and mechanism—severity of stove and tap water scalds reduced in intervention area but ﬁgures only reported for control area. No P values reported
Zhao [30]	RCT A–N B–Y F–Y	Primary school children aged 7 to 13 N = 5872, year 2000 N = 5880, year 2001	I: school based Health education to children and their parents on injury prevention including scalds prevention; safety storage of pot of hot water C: school based health education of other common childhood diseases	Scald injuries Self-reported scalds/burns 1 year after intervention I = 28 (0.88%), C = 25 (0.93%); not significant (p value not given) Self-reported scalds/burns 2 years after intervention I = 10 (0.31%), C = 18 (0.68%), p < 0.05

Risk of bias: A = allocation concealment, B = blinding of outcome assessment, F = follow up on ≥80% of participants, C = confounder balanced between groups, Y = adequate, N = not adequate, U = unclear.

Bias of case-control and cohort studies was assessed using Newcastle—Ottawa quality assessment scale (NOS).

Minkovitz [53] reported 1 RCT and 1 CBA.