Functional capacity and muscle strength outcomes
| Outcome measures | VU | CS | NS | P-value |
|---|---|---|---|---|
| Handgrip strength (kg) | 26.3 ± 1.8 | 22.9 ± 1.7 | 33.5 ± 1.9 | <0.001* |
| 6-minute walk distance (m) | 481.5 ± 47.8 | 437.8 ± 51.9 | 509.6 ± 46.3 | <0.001* |
| mMRC dyspnoea score (0–4) | 1.2 ± 0.5 | 2.1 ± 0.6 | 0.8 ± 0.4 | <0.001* |
Traditional CS only (N = 40)
| Variable | Age (years) | BMI (kg/m2) | Smoking duration | Pack-years | Nicotine level | Dyspnoea score | Hand grip strength | 6MWT distance |
|---|---|---|---|---|---|---|---|---|
| Age (years) | 1.00 | 0.12 | 0.85** | 0.82** | -0.08 | 0.45* | -0.52* | -0.61** |
| BMI (kg/m2) | 0.12 | 1.00 | 0.15 | 0.18 | 0.22 | 0.31 | -0.28 | -0.35* |
| Smoking duration | 0.85** | 0.15 | 1.00 | 0.95** | -0.12 | 0.52* | -0.58** | -0.67** |
| Pack-years | 0.82** | 0.18 | 0.95** | 1.00 | -0.15 | 0.55** | -0.62** | -0.71** |
| Nicotine level | -0.08 | 0.22 | -0.12 | -0.15 | 1.00 | 0.18 | -0.21 | -0.24 |
| Dyspnoea score | 0.45* | 0.31 | 0.52* | 0.55** | 0.18 | 1.00 | -0.73** | -0.81** |
| Hand grip strength | -0.52* | -0.28 | -0.58** | -0.62** | -0.21 | -0.73** | 1.00 | 0.86** |
| 6MWT distance | -0.61** | -0.35* | -0.67** | -0.71** | -0.24 | -0.81** | 0.86** | 1.00 |
NS only (N = 40)
| Variable | Age (years) | BMI (kg/m2) | Dyspnoea score | Hand grip strength | 6MWT distance |
|---|---|---|---|---|---|
| Age (years) | 1.00 | 0.14 | 0.22 | -0.28 | -0.35* |
| BMI (kg/m2) | 0.14 | 1.00 | 0.25 | -0.30 | -0.38* |
| Dyspnoea score | 0.22 | 0.25 | 1.00 | -0.65** | -0.72** |
| Hand grip strength | -0.28 | -0.30 | -0.65** | 1.00 | 0.83** |
| 6MWT distance | -0.35* | -0.38* | -0.72** | 0.83** | 1.00 |
Descriptive characteristics of study participants
| Characteristics | VU (n = 40) | CS (n = 40) | NS (n = 40) | P-value |
|---|---|---|---|---|
| Demographics | ||||
| Age (years) | 49.5 ± 6.2 | 50.2 ± 6.3 | 49.8 ± 6.1 | 0.891 |
| BMI (kg/m2) | 24.4 ± 2.7 | 24.6 ± 2.8 | 24.3 ± 2.6 | 0.901 |
| Smoking history | ||||
| Duration (years) | 10.5 ± 2.9 | 22.8 ± 7.1 | - | <0.001* |
| Packs/day equivalent | 1.56 ± 0.15 | 1.02 ± 0.12 | - | <0.001* |
| Pack-years equivalent | 16.4 ± 4.5 | 23.3 ± 7.2 | - | <0.001* |
| Nicotine exposure (mg/day) | 45.0 ± 1.5 | 28.8 ± 1.2 | - | <0.001* |
Correlations between functional outcome measures
| Groups | Handgrip versus 6MWT | Handgrip versus dyspnoea | 6MWT versus dyspnoea | |||
|---|---|---|---|---|---|---|
| r | P | r | P | R | P | |
| CS (n = 40) | 0.86 | <0.01 | -0.73 | <0.01 | -0.81 | <0.01 |
| VU (n = 40) | 0.82 | <0.01 | -0.68 | <0.01 | -0.75 | <0.01 |
| NS (n = 40) | 0.83 | <0.01 | -0.65 | <0.01 | -0.72 | <0.01 |
Correlation between smoking exposure and functional outcomes in CS
| Variables | Handgrip strength | 6MWT distance | Dyspnoea score | |||
|---|---|---|---|---|---|---|
| r | P | r | P | R | P | |
| Duration (years) | -0.58 | <0.01 | -0.67 | <0.01 | 0.52 | <0.05 |
| Pack-years | -0.62 | <0.01 | -0.71 | <0.01 | 0.55 | <0.01 |
| Packs/day | -0.48 | <0.01 | -0.53 | <0.01 | 0.41 | <0.05 |
| Nicotine exposure (mg/day) | -0.21 | -0.21 | -0.24 | -0.24 | 0.18 | 0.18 |
Correlation between vaping exposure and functional outcomes in VU
| Variables | Handgrip strength | 6MWT distance | Dyspnoea score | |||
|---|---|---|---|---|---|---|
| R | P | r | P | r | P | |
| Duration (years) | -0.52 | <0.05 | -0.61 | <0.01 | 0.45 | <0.05 |
| Pack-years equivalent | -0.55 | <0.01 | -0.64 | <0.01 | 0.48 | <0.05 |
| Packs/day equivalent | -0.44 | <0.01 | -0.49 | <0.01 | 0.38 | <0.05 |
| Nicotine exposure (mg/day) | -0.35 | <0.05 | -0.42 | <0.05 | 0.32 | 0.32 |
E-cigarette (vape) users only (N = 40)
| Variable | Age (years) | BMI (kg/m2) | Usage duration | Pack-years | Nicotine level | Dyspnoea score | Hand grip strength | 6MWT distance |
|---|---|---|---|---|---|---|---|---|
| Age (years) | 1.00 | 0.18 | 0.78** | 0.75** | -0.15 | 0.38* | -0.45* | -0.52* |
| BMI | 0.18 | 1.00 | 0.22 | 0.25 | 0.18 | 0.28 | -0.32 | -0.41* |
| Usage duration | 0.78** | 0.22 | 1.00 | 0.92** | -0.08 | 0.45* | -0.52* | -0.61** |
| Pack-years | 0.75** | 0.25 | 0.92** | 1.00 | -0.12 | 0.48* | -0.55** | -0.64** |
| Nicotine level | -0.15 | 0.18 | -0.08 | -0.12 | 1.00 | 0.32 | -0.35* | -0.42* |
| Dyspnoea score | 0.38* | 0.28 | 0.45* | 0.48* | 0.32 | 1.00 | -0.68** | -0.75** |
| Hand grip strength | -0.45* | -0.32 | -0.52* | -0.55** | -0.35* | -0.68** | 1.00 | 0.82** |
| 6MWT distance | -0.52* | -0.41* | -0.61** | -0.64** | -0.42* | -0.75** | 0.82** | 1.00 |