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Table 2 Comparison of controls and e-Cigarette users at baseline, 12-month and 24-month follow-up visits

From: Evidence for harm reduction in COPD smokers who switch to electronic cigarettes

  Baseline 12-Month Follow-up Within group p value vs BaselineΩ 24-Month Follow-up Within group P value vs BaselineΩ Overall between group p value from Baselineƙ
COPD Controls (n = 24)
 post-BD FEV1a (L) 1.47 (1.13, 1.72) 1.43 (1.12, 172) 0.538 1.45 (1.17, 1.66) 0.657 0.223
 post-BD FVCa (L) 2.39 (2.1, 2.64) 2.35 (2.2, 2.74) 0.065 2.35 (2.19, 2.83) 0.141 0.977
 %FEV1/FVCb 56.2 (±10.3) 55.9 (±10.1) 0.328 56.3 (±10.1) 0.277 0.033
 Cig/dayb 20.5 (±3.3) 20.1 (±3.7) 0.371 19.8 (±5) 0.296 <0.001
 CAT scorea 20.5 (17.8, 24.3) 20 (17.5, 24.3) 0.075 20 (15.8, 24) 0.361 0.001
 COPD Exacerbationsb 2.1 (±1.1) 2.2 (±1) 0.906 2.1 (±1.1) 0.819 0.005
 6MWDa, c 267.3 (195, 351.5) 270 (210.3, 372) 0.056 270.5 (220.8, 373.9) 0.096 0.002
COPD EC users (n = 24)
 post-BD FEV1a (L) 1.25 (0.94, 1.78) 1.23 (0.93, 1.73) 0.102 1.29 (0.92, 1.67) 0.153  
 post-BD FVCa (L) 2.37 (2, 2.65) 2.45 (1.92, 2.73) 0.081 2.46 (1.84, 2.86) 0.252
 %FEV1/FVCb 59.4 (±8.4) 58.3 (±8.6) 0.457 57.9 (±8.5) 0.483
 Cig/dayb 21.8 (±4.4) 1.8 (±2.2) <0.001 1.58 (±2) <0.001
 CAT scorea 21.5 (17.8, 25.3) 17.5 (15.8, 20.5) <0.001 18 (15, 20) <0.001
 COPD Exacerbationsb 2.3 (±1) 1.8 (±1) 0.002 1.4 (±0.9) <0.001
 6MWDa, c 266.5 (187.5, 313.5) 307 (219.5, 342) 0.002 327 (239.5, 359.5) 0.002
  1. Abbreviations: COPD Chronic obstructive pulmonary disease, EC e-Cigarette, n number, BD bronchodilator, L litre, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity, Cig conventional cigarettes, CAT COPD assessment tool, 6MWD 6 min walk distance
  2. a Median (interquartile range); b Mean (± standard deviation)
  3. c 13 subjects in the COPD E-Cig user group and 14 in the COPD control group
  4. Ω Statistical analyses conducted using Mann Whitney U Test (as data non-parametric) except for Cig/day and COPD exacerbations which were analysed using student T test (parametric data)
  5. ƙ Statistical analyses conducted using repeated measures ANOVA with Bonferroni adjustment