Health effects in COPD smokers who switch to electronic cigarettes: a retrospective-prospective 3-year follow-up

Figures & data

Table 1 Baseline demographics of study participants (before switching to electronic cigarettes)

Parameter	COPD controls (n=22)	COPD EC users (n=22)	Baseline p-value between groups
Age¥	65.2 (±5.6)	66.5 (±6.8)	0.518
Sex	19 M, 3 F	18 M, 4 F	–
COPD GOLD staging
Stage 1	2	2	–
Stage 2	5	6	–
Stage 3	10	9	–
Stage 4	5	5	–
Post-BD FEV1* (L)	1.47 (1.17, 1.69)	1.25 (0.97, 1.82)	0.445
Post-BD FVC* (L)	2.34 (2.09, 2.63)	2.49 (2.3, 2.65)	0.787
%FEV1/FVC¥	59.7 (±7.8)	56.2 (±10.7)	0.221
Pack-years of smoking¥	51.8 (±10.4)	52.2 (±11.1)	0.900
Cig/day¥	20.8 (±4.6)	21.9 (±4.5)	0.221
CAT score*	20 (17.3, 24.8)	21.0 (17.3, 25.0)	0.832
COPD exacerbations¥	2.1 (±1.1)	2.3 (±0.9)	0.657
6MWD* (m)	284.5 (217.5, 365)	289.5 (186.5, 344.8)	0.817

Notes:

* Median (interquartile range);

¥ mean (± standard deviation).

Abbreviations: 6MWD, 6-minute walk distance; BD, bronchodilator; CAT, COPD Assessment Tool; Cig, conventional cigarettes; COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; F, female; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; M, male.

Table 2 Changes in study parameters from baseline at 12-, 24-, and 36-month follow-up visits in COPD controls and COPD EC users

	Baseline	12-month follow-up	Within-group p-value vs baseline	24-month follow-up	Within-group p-value vs baseline	36-month follow-up	Within-group p-value vs baseline	Overall between-group p-value from baseline
COPD controls (n=22)
Post-BD FEV1* (L)	1.47 (1.17, 1.69)	1.43 (1.15, 1.69)	0.614	1.45 (1.18, 1.64)	0.845	1.47 (1.18, 1.64)	0.697	0.233
Post-BD FVC* (L)	2.34 (2.09, 2.63)	2.30 (2.19, 2.71)	0.094	2.32 (2.17, 2.77)	0.194	2.28 (2.06, 2.57)	0.073	0.077
%FEV1/FVC	59.7 (±7.8)	58.7 (±7.7)	0.008	58.5 (±7.7)	0.001	60.2 (±9.3)	0.664	0.454
Cig/day¥	20.8 (±4.6)	20.4 (±3.7)	0.776	20.1 (±5.0)	0.657	19.5 (±3.8)	0.330	<0.001
CAT score*	20 (17.3, 24.8)	20 (20, 24.8)	0.162	20 (15.3, 24)	0.512	20 (18, 23.5)	0.662	0.019
COPD exacerbations¥	2.1 (±1.1)	2.2 (0.9)	0.740	2.1 (±1.1)	0.825	2.1 (±0.9)	1.000	0.004
6MWD*,# (m)	284.5 (217.5, 365)	270 (211, 392)	0.087	277.5 (235, 401.5)	0.133	277 (220.5, 425)	0.087	0.001
COPD EC users (n=22)
Post-BD FEV1* (L)	1.25 (0.97, 1.82)	1.23 (0.95, 1.76)	0.118	1.29 (0.94, 1.68)	0.173	1.30 (0.99, 1.74)	0.071
Post-BD FVC* (L)	2.49 (2.3, 2.65)	2.51 (2.0 2.74)	0.101	2.46 (1.92, 2.89)	0.284	2.54 (1.96, 2.88)	0.085
%FEV1/FVC¥	56.2 (±10.7)	55.9 (±10.5)	0.470	56.4 (±10.4)	0.693	56.8 (±10.2)	0.480
Cig/day¥	21.9 (±4.5)	2 (±2.2)	<0.001	1.6 (±2)	<0.001	1.5 (±2.4)	<0.001
CAT score*	21.0 (17.3, 25.0)	17.5 (16, 20)	<0.001	18 (15, 20)	<0.001	15.5 (12.5, 23.5)	0.007
COPD exacerbations¥	2.3 (±0.9)	1.7 (±1)	0.002	1.4 (±0.9)	0.002	1.3 (±0.9)	<0.001
6MWD*,# (m)	289.5 (186.5, 344.8)	310 (218.3, 371.8)	0.004	333 (230.3, 374.8)	0.004	359.5 (251, 399.8)	0.003

Notes:

* Median (interquartile range);

¥ mean (± standard deviation).

# Thirteen subjects in the COPD EC user group and 14 in the COPD control group at 12- and 24-month review. At 36-month review, 11 subjects in the EC group and 13 subjects in the control group. Values shown in bold are statistically significant.

Abbreviations: COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; n, number; BD, bronchodilator; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; Cig, conventional cigarettes; CAT, COPD Assessment Tool; 6MWD, 6-minute walk distance.

Table 3 Changes in study parameters from baseline at 12-, 24-, and 36-month follow-up visits in single and dual users

Parameters	Baseline	12-month follow-up	Within-group p-value vs baseline	24-month follow-up	Within-group p-value vs baseline	36-month follow-up	Within-group p-value vs baseline
COPD EC users reducing Cig use (dual users)	(n=9)	(n=11)	–	(n=10)	–	(n=9)	–
Sex	9 M	10 M, 1 F	–	10 M	–	9 M	–
% smoking reduction compared to baseline	–	82.7 (±4.8)	–	85.1 (±4.7)	–	83.5 (±6.3)	–
Post-BD FEV1* (L)	0.99 (0.96, 1.84)	1.2 (0.91, 1.7)	0.026	1.18 (0.91, 2.01)	0.054	1.25 (0.9, 1.8)	0.132
Post-BD FVC* (L)	2.34 (2.16, 3.13)	2.35 (2.07, 2.89)	0.074	2.52 (2.2, 2.93)	0.162	2.52 (2.2, 2.89)	0.202
%FEV/FVC*	52.1(±9.5)	53.8 (±9.9)	1.000	54.0 (±12.1)	0.863	52.0 (±10)	0.906
Cig/day¥	23.9 (±4.9)	4 (±1.2)	<0.001	3.6 (±1.3)	<0.001	3.8 (±1.1)	<0.001
CAT score*	24 (21, 27)	20 (18, 22)	<0.001	19 (16, 22)	0.005	20 (14, 25)	0.022
COPD exacerbations¥	2.7 (±0.9)	2.3 (±0.8)	0.104	1.5 (±0.9)	0.002	1.2 (±0.8)	0.001
COPD EC users ceasing Cig use (single users)	(n=13)	(n=11)		(n=12)		(n=13)
Sex	9 M, 4 F	8 M, 3 F		8 M, 4 F		9 M, 4 F
Smoking reduction compared to baseline	–	–		–		–
Post-BD FEV1* (L)	1.32 (1.05, 1.76)	1.26 (1.02, 1.75)	0.886	1.34 (1.14, 1.64)	0.607	1.47 (1.1, 1.65)	0.254
Post-BD FVC* (L)	2.57 (2.01, 2.65)	2.6 (2.7, 2.73)	0.677	2.44 (1.81, 2.83)	0.628	2.55 (1.8, 2.86)	0.277
%FEV/FVC*	59.0 (±10.3)	58 (±11)	0.188	58.4 (±8.8)	0.509	60.1 (±9.3)	0.372
Cig/day¥	20.5 (±3.8)	–		–		–
CAT score*	18 (17, 24)	16 (15, 18)	0.002	16 (15, 19)	0.004	14 (12, 20)	0.018
COPD exacerbations¥	2.0 (±0.9)	1.2 (±1)	0.012	1.3 (±1)	0.021	1.3 (±1)	0.044

Notes:

* Median (interquartile range);

¥ mean (± standard deviation). The values shown in bold are statistically significant.

Abbreviations: n, number; COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; M, male; F, female; BD, bronchodilator; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; Cig, conventional cigarettes; CAT, COPD Assessment Tool.

Figure 1 Changes in the number of COPD exacerbations per year from baseline, at follow-up visit 1 (12±1.5 months), visit 2 (24±2.5 months), and visit 3 (36±3 months) separately for COPD EC users (closed triangles) and COPD controls (closed circles). All data are expressed as mean and error bars are standard deviation of the mean. The ** and *** indicate the within-group p-value of <0.01 and <0.001, respectively, compared to baseline.

Abbreviations: COPD, chronic obstructive pulmonary disease; EC, electronic cigarette.

Figure 2 Changes in the FEV₁ (A) and FVC (B) from baseline, at follow-up visit 1 (12±1.5 months), visit 2 (24±2.5 months), and visit 3 (36±3 months) separately for COPD EC users (dark gray boxes) and COPD controls (light gray boxes). The boxes represent the 25th to 75th percentiles; the line in the boxes indicates the median, and error bars are 5th and 95th percentiles.

Abbreviations: COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; BL, baseline.

Figure 3 COPD GOLD stage changes over the study period.

Abbreviations: COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; BL, baseline; GOLD, Global Initiative for Chronic Obstructive Lung Disease.

Figure 4 Changes in the CAT scores from baseline, at follow-up visit 1 (12±1.5 months), visit 2 (24±2.5 months), and visit 3 (36±3 months) separately for COPD EC users (dark gray boxes) and COPD controls (light gray boxes). The boxes represent the 25th to 75th percentiles; the lines in the boxes indicate the median, and error bars are 5th and 95th percentiles. The ** and *** indicate the within-group p-value of <0.01 and <0.001, respectively, compared to baseline.

Abbreviations: COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; BL, baseline; CAT, COPD Assessment Tool.