What do systematic reviews say?

Higher vs lower degree of injury

It is very uncertain whether higher changes clinical pregnancy per woman randomised: sensitivity analysis… compared with lower degree of injury (very low certainty).

• Endometrial injury in women undergoing in vitro fertilisation (IVF) 2021 · Cochrane Headline outcomes only
  OR 1.31 [0.46, 3.73]
  1 study · 129 participants
  Very low

Higher vs lower intensity motivational interviewing

Higher may leads to higher smoking cessation at ≥ 6 months compared with lower intensity motivational interviewing (low certainty).

• Motivational interviewing for smoking cessation 2019 · Cochrane Headline outcomes only
  RR 1.23 [1.11, 1.37]
  5 studies · 5620 participants
  Low

Higher vs lower omega‐6: additional key outcomes

Higher showed no clear difference in all‐cause mortality Study duration range 12‐96 months Omega‐6 dose… compared with lower omega‐6: primary outcomes (low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 1 [0.88, 1.12]
  10 studies · 4506 participants
  Low

Higher vs lower omega‐6: additional key outcomes

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  no estimate extracted
  2 studies · 244 participants
  Low

Higher vs lower omega‐6: additional key outcomes

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  no estimate extracted
  4 studies · 1995 participants
  Low

Higher vs lower omega‐6: additional key outcomes

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  no estimate extracted
  4 studies · 358 participants
  Very low

Higher vs lower omega‐6: additional key outcomes

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 371 participants
  Moderate

Higher vs lower omega‐6: additional key outcomes

It is very uncertain whether higher changes cardiovascular mortality Study duration range 24‐96 months Omega‐6… compared with lower omega‐6: primary outcomes (very low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 1.09 [0.76, 1.55]
  7 studies · 4019 participants
  Very low

Higher vs lower omega‐6: additional key outcomes

Higher showed no clear difference in cardiovascular events: any Study duration range 12‐96 months Omega‐6… compared with lower omega‐6: primary outcomes (low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 0.97 [0.81, 1.15]
  7 studies · 4962 participants
  Low

Higher vs lower omega‐6: additional key outcomes

It is very uncertain whether higher changes CHD events: myocardial infarction (fatal or non‐fatal) or angina… compared with lower omega‐6: primary outcomes (very low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 0.88 [0.66, 1.17]
  7 studies · 3997 participants
  Very low

Higher vs lower omega‐6: additional key outcomes

It is very uncertain whether higher changes MACCEs Study duration range 24‐96 months Omega‐6 dose range… compared with lower omega‐6: primary outcomes (very low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 0.84 [0.59, 1.2]
  2 studies · 2879 participants
  Very low

Higher vs lower omega‐6: additional key outcomes

It is very uncertain whether higher changes stroke: fatal or non‐fatal Study duration range 24‐96 months Omega‐6… compared with lower omega‐6: primary outcomes (very low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 1.36 [0.45, 4.11]
  4 studies · 3730 participants
  Very low

Higher vs lower omega‐6: additional key outcomes

Higher showed no clear difference in MI Study duration range 12‐96 months Omega‐6 dose range 2.8%‐24.5% E compared with lower omega‐6: additional key outcomes (low certainty).

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  RR 0.88 [0.76, 1.02]
  7 studies · 4606 participants
  Low

Higher vs lower omega‐6: additional key outcomes

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  no estimate extracted
  10 studies · 4280 participants
  High

Higher vs lower omega‐6: additional key outcomes

• Omega‐6 fats for the primary and secondary prevention of cardiovascular disease 2018 · Cochrane Headline outcomes only
  no estimate extracted
  5 studies · 834 participants
  Low

Higher vs lower PUFA

It is very uncertain whether higher changes all allergic disease ‐ infant incidence compared with lower PUFA intake (very low certainty).

• Polyunsaturated fatty acid supplementation in infancy for the prevention of allergy 2016 · Cochrane Headline outcomes only
  RR 0.96 [0.73, 1.26]
  1 study · 323 participants
  Very low

Higher vs lower PUFA

It is very uncertain whether higher changes all allergic disease ‐ childhood prevalence compared with lower PUFA intake (very low certainty).

• Polyunsaturated fatty acid supplementation in infancy for the prevention of allergy 2016 · Cochrane Headline outcomes only
  RR 0.98 [0.81, 1.19]
  2 studies · 633 participants
  Very low

Higher vs lower PUFA

It is very uncertain whether higher changes asthma ‐ childhood prevalence compared with lower PUFA intake (very low certainty).

• Polyunsaturated fatty acid supplementation in infancy for the prevention of allergy 2016 · Cochrane Headline outcomes only
  RR 1.12 [0.82, 1.53]
  2 studies · 635 participants
  Very low

Higher vs lower PUFA

It is very uncertain whether higher changes dermatitis/eczema ‐ childhood prevalence compared with lower PUFA intake (very low certainty).

• Polyunsaturated fatty acid supplementation in infancy for the prevention of allergy 2016 · Cochrane Headline outcomes only
  RR 0.81 [0.59, 1.09]
  2 studies · 635 participants
  Very low

Higher vs lower PUFA

It is very uncertain whether higher changes allergic rhinitis ‐ childhood prevalence compared with lower PUFA intake (very low certainty).

• Polyunsaturated fatty acid supplementation in infancy for the prevention of allergy 2016 · Cochrane Headline outcomes only
  RR 1.02 [0.83, 1.25]
  2 studies · 635 participants
  Very low