Table 2

Quality of evidence for determinants and outcomes of physical activity in COPD, as identified in 86 studies

DeterminantN studiesDirection establishedControl for confoundingDirectnessConsistencyStrengthLow precisionOtherConfidence rating
(A) Quality of evidence for socio-demographic, lifestyle and environmental determinants of physical activity
AgeS30 S33 S34 S57 S71 S816nanaYes−11NoNoNo+++ (moderate)
Alcohol consumptionS30 S342−22−14Yes−11No−16No+ (very low)
Cultural groupS14 S59 S713−12na−13−11NoNoNo+ (very low)
Day of the weekS45 S49 S823−22−14Yes−11NoNoNo+ (very low)
EducationS30 S33 S343−22−14Yes−11NoNoNo+ (very low)
Marital statusS30 S332−22−14Yes−11NoNoNo+ (very low)
SexS30 S33 S34 S57 S68 S816nanaYes−11NoNoNo+++ (moderate)
Smoking habitS30 S33 S343−22−14Yes−11No−16No+ (very low)
Socioeconomic statusS30 S332−22−15Yes−11NoNoNo+ (very low)
Working statusS30 S33 S343−22−14Yes−11NoNoNo+ (very low)
(B) Quality of evidence for functional and clinical determinants of physical activity
BODE indexS34 S49 S57 S81 S83 5−22−15Yes−11NoNoNo+ (very low)
Body mass indexS30 S34 S48 S57 S81 5−22−15Yes−11NoNoNo+ (very low)
CardiovascularS30 S81 2−22−15Yes−11No−16−17+ (very low)
DyspnoeaS8 S41 S30 S34 S52 S57 S83 7−22−15YesyesNoNoNo+ (very low)
Emotional statusS30 S522−22YesYes−11NoNoNo+ (very low)
Exercise capacity (VO2 max, 6MWD)S1 S6 S34 S37 S49 S52 S57 S74 S83 9−22−15YesyesNoNoNo+ (very low)
FEV1S6 S22 S30 S34 S41 S42 S49 S57 S58 S71 S81 S82 S83 S8614−12−15Yes−11NoNoNo+ (very low)
FVCS34 S572−12YesYes−11NoNo−112+ (very low)
Gas exchange (DLco)S34 S742−22−14YesyesNoNoNo+ (very low)
Gas exchange (PCO2)S30 S342−22−14YesyesNoNoNo+ (very low)
Gas exchange (PO2)S30 S342−22−14YesyesNoNoNo+ (very low)
HyperinflationS34 S37 S42 S57 S585−22YesYesyesNoNoNo++ (low)
Osteoarticular conditionS30 S492−22−14Yes−11No−16No+ (very low)
Previous exacerbationS11 S30 S563−12−14YesyesNoNo−17+ (very low)
Quality of life/health-related quality of lifeS1 S30 S34 S49 S57 5−22−14YesyesNoNoNo+ (very low)
Self-efficacyS1 S372−22YesYesyesNoNo−17+ (very low)
Systemic inflammationS34 S812−22−15YesyesNoNo−17+ (very low)
(C) Quality of evidence for interventions to modify levels of physical activity
Dietary interventionS16 S842YesYesYes−11NoNo−112++ (low)
Exercise trainingS3 S4 S7 S12 S15 S17 S18 S20 S21 S27 S28 S46 S53 S60 S61 S64 S65 S66 S69 S70 S79 21Yes−18Yes−11NoNoNo++ (low)
Long-acting β2 agonist/corticosteroidsS30 S34 S383−22−18Yes−11No−16No+ (very low)
Long-term oxygen therapyS30 S34 S54 S63 S72 S75 6YesYesYes−11NoNo−110,11++ (low)
Physical activity adviceS19 S51 S853Yes−18Yes−11No−19No+ (very low)
(D) Quality of evidence for outcomes as a result of different levels of physical activity
BalanceS2 S622−12−18Yes−11NoNo−112,13+ (very low)
Bone mineral densityS9 S672−22−18Yes−11NoNo−113+ (very low)
DyspnoeaS33 S442−12YesYesYesNoNo−113++ (low)
ExacerbationsS5 S14 S29 S31 S32 S35 S50 S56 8YesYesYesYesNoNo−113+++ (moderate)
Exercise capacity (6MWD)S13 S23 S33 S76 4−12YesYesYesNoNo−113++ (low)
FEV1S33 S442−22YesYesYesNoNo−113+ (very low)
MortalityS24 S26 S31 S32 S35 S55 S807YesYesYesYesNoNo−113+++ (moderate)
Quality of life/health-related quality of lifeS24 S25 S40 S444YesYesYes−11NoNo−113++ (low)
  • Interpretation of the categories of the quality of evidence: + (very low), there is a little confidence in the effect estimate, the true effect is likely to be substantially different from the estimate of effect; ++ (low), the confidence in the effect estimated is limited, the true effect may be substantially different from the estimate of the effect; +++ (moderate), there is a moderate confidence that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different; and ++++ (high), there is high confidence that the true effect lies close to that of the estimate of the effect.

  • Reasons for upgrading or downgrading:

  • 1Inconsistent effects (eg, different direction of effects) across and/or within studies with statistically significant and/or non-significant results.

  • 2Direction could not be established because the majority (–1) or all (–2) studies were cross-sectional studies.

  • 3The majority of studies included some sources of highly selected population (patients candidates for lung volume reduction surgery, patients with very severe COPD or patients included in a rehabilitation programme).

  • 4No control for confounding.

  • 5Only some studies had some control for confounding.

  • 6Determinant was self-reported in most/all studies.

  • 7The measures of exposure were so different that results could not be compared.

  • 8The majority of studies without control group.

  • 995% CIs too wide to interpret the effect estimates.

  • 10Measures of physical activity too different to allow comparison of results across studies.

  • 11Potential confounding by indication.

  • 12Studies with small to moderate sample size.

  • 13Too few measures of physical activity (eg, only indirect and no activity monitor) to judge association with physical activity.

  • DLCO, Diffusing Lung capacity for carbon monoxide; FEV1, Forced Expiratory Volume in the first second; FVC, Forced Vital Capacity; PCO2, Partial Pressure of Carbon Dioxide; PO2, Partial Pressure of Oxygen; VO2 max, Maximal Oxygen Uptake; 6MWD, 6 min walk distance.