Exercise Protects Bone after Stroke, or Does It? A Narrative Review of the Evidence

Table 4

Levels of evidence for intervention studies.

Level of evidence	Type of evidence
1++	High-quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low risk of bias.
1+	Well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias.
1−	Meta-analyses, systematic reviews of RCTs, or RCTs with a high risk of bias.*
2++	High-quality systematic reviews of case-control or cohort studies. High-quality case-control or cohort studies with a very low risk of confounding, bias orchance and a high probability that the relationship is causal.
2+	Well-conducted case-control or cohort studies with a low risk of confounding, bias orChance, and a moderate probability that the relationship is causal.
2−	Case control or cohort studies with a high risk of confounding, bias or chance, and asignificant risk that the relationship is not causal.*
3	Nonanalytic studies (e.g., case reports and case series).
4	Expert opinion, formal consensus.

*Studies with a level of evidence “–” are not used as a basis for making a recommendation.
RCT, randomised controlled trial.
National Institute for Health and Clinical Excellence, The guidelines manual 2007, ed. NICE. 2007, London [76].