Table 2

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

Determinant	N studies	Direction established	Control for confounding	Directness	Consistency	Strength	Low precision	Other	Confidence rating
(A) Quality of evidence for socio-demographic, lifestyle and environmental determinants of physical activity
Age^{S30 S33 S34 S57 S71 S81}	6	na	na	Yes	−1¹	No	No	No	+++ (moderate)
Alcohol consumption^{S30 S34}	2	−2²	−1⁴	Yes	−1¹	No	−1⁶	No	+ (very low)
Cultural group^{S14 S59 S71}	3	−1²	na	−1³	−1¹	No	No	No	+ (very low)
Day of the week^{S45 S49 S82}	3	−2²	−1⁴	Yes	−1¹	No	No	No	+ (very low)
Education^{S30 S33 S34}	3	−2²	−1⁴	Yes	−1¹	No	No	No	+ (very low)
Marital status^{S30 S33}	2	−2²	−1⁴	Yes	−1¹	No	No	No	+ (very low)
Sex^{S30 S33 S34 S57 S68 S81}	6	na	na	Yes	−1¹	No	No	No	+++ (moderate)
Smoking habit^{S30 S33 S34}	3	−2²	−1⁴	Yes	−1¹	No	−1⁶	No	+ (very low)
Socioeconomic status^{S30 S33}	2	−2²	−1⁵	Yes	−1¹	No	No	No	+ (very low)
Working status^{S30 S33 S34}	3	−2²	−1⁴	Yes	−1¹	No	No	No	+ (very low)
(B) Quality of evidence for functional and clinical determinants of physical activity
BODE index^{S34 S49 S57 S81 S83}	5	−2²	−1⁵	Yes	−1¹	No	No	No	+ (very low)
Body mass index^{S30 S34 S48 S57 S81}	5	−2²	−1⁵	Yes	−1¹	No	No	No	+ (very low)
Cardiovascular^{S30 S81}	2	−2²	−1⁵	Yes	−1¹	No	−1⁶	−1⁷	+ (very low)
Dyspnoea^{S8 S41 S30 S34 S52 S57 S83}	7	−2²	−1⁵	Yes	yes	No	No	No	+ (very low)
Emotional status^{S30 S52}	2	−2²	Yes	Yes	−1¹	No	No	No	+ (very low)
Exercise capacity (VO₂ max, 6MWD)^{S1 S6 S34 S37 S49 S52 S57 S74 S83}	9	−2²	−1⁵	Yes	yes	No	No	No	+ (very low)
FEV₁^{S6 S22 S30 S34 S41 S42 S49 S57 S58 S71 S81 S82 S83 S86}	14	−1²	−1⁵	Yes	−1¹	No	No	No	+ (very low)
FVC^{S34 S57}	2	−1²	Yes	Yes	−1¹	No	No	−1¹²	+ (very low)
Gas exchange (DLco)^{S34 S74}	2	−2²	−1⁴	Yes	yes	No	No	No	+ (very low)
Gas exchange (PCO₂)^{S30 S34}	2	−2²	−1⁴	Yes	yes	No	No	No	+ (very low)
Gas exchange (PO₂)^{S30 S34}	2	−2²	−1⁴	Yes	yes	No	No	No	+ (very low)
Hyperinflation^{S34 S37 S42 S57 S58}	5	−2²	Yes	Yes	yes	No	No	No	++ (low)
Osteoarticular condition^{S30 S49}	2	−2²	−1⁴	Yes	−1¹	No	−1⁶	No	+ (very low)
Previous exacerbation^{S11 S30 S56}	3	−1²	−1⁴	Yes	yes	No	No	−1⁷	+ (very low)
Quality of life/health-related quality of life^{S1 S30 S34 S49 S57}	5	−2²	−1⁴	Yes	yes	No	No	No	+ (very low)
Self-efficacy^{S1 S37}	2	−2²	Yes	Yes	yes	No	No	−1⁷	+ (very low)
Systemic inflammation^{S34 S81}	2	−2²	−1⁵	Yes	yes	No	No	−1⁷	+ (very low)
(C) Quality of evidence for interventions to modify levels of physical activity
Dietary intervention^{S16 S84}	2	Yes	Yes	Yes	−1¹	No	No	−1¹²	++ (low)
Exercise training^{S3 S4 S7 S12 S15 S17 S18 S20 S21 S27 S28 S46 S53 S60 S61 S64 S65 S66 S69 S70 S79}	21	Yes	−1⁸	Yes	−1¹	No	No	No	++ (low)
Long-acting β2 agonist/corticosteroids^{S30 S34 S38}	3	−2²	−1⁸	Yes	−1¹	No	−1⁶	No	+ (very low)
Long-term oxygen therapy^{S30 S34 S54 S63 S72 S75}	6	Yes	Yes	Yes	−1¹	No	No	−1^10,11	++ (low)
Physical activity advice^{S19 S51 S85}	3	Yes	−1⁸	Yes	−1¹	No	−1⁹	No	+ (very low)

Outcome

(D) Quality of evidence for outcomes as a result of different levels of physical activity
Balance^{S2 S62}	2	−1²	−1⁸	Yes	−1¹	No	No	−1^12,13	+ (very low)
Bone mineral density^{S9 S67}	2	−2²	−1⁸	Yes	−1¹	No	No	−1¹³	+ (very low)
Dyspnoea^{S33 S44}	2	−1²	Yes	Yes	Yes	No	No	−1¹³	++ (low)
Exacerbations^{S5 S14 S29 S31 S32 S35 S50 S56}	8	Yes	Yes	Yes	Yes	No	No	−1¹³	+++ (moderate)
Exercise capacity (6MWD)^{S13 S23 S33 S76}	4	−1²	Yes	Yes	Yes	No	No	−1¹³	++ (low)
FEV₁^{S33 S44}	2	−2²	Yes	Yes	Yes	No	No	−1¹³	+ (very low)
Mortality^{S24 S26 S31 S32 S35 S55 S80}	7	Yes	Yes	Yes	Yes	No	No	−1¹³	+++ (moderate)
Quality of life/health-related quality of life^{S24 S25 S40 S44}	4	Yes	Yes	Yes	−1¹	No	No	−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.