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Table 1 Characteristics of total enrolled study sample and analytical study sample

From: Use of electronic cigarettes and secondhand exposure to their aerosols are associated with asthma symptoms among adolescents: a cross-sectional study

Variables Total study sample (n = 1565) Analytical study sample* (n = 1345)
Sex, n (%)
 Female 836 (53.4) 697 (51.8)
 Male 729 (46.6) 648 (48.2)
Age groups, n (%)
 ≤ 16 years 386 (25.1) 336 (25.4)
 17 years 843 (54.7) 712 (53.8)
 ≥ 18 years 311 (20.2) 276 (20.8)
 Missing, n 25 21
Electronic cigarette use, n (%)
 Never 957 (61.9) 812 (60.4)
 Former 182 (11.8) 164 (12.2)
 Current (any use in past 30 days) 408 (26.3) 369 (27.4)
 Missing, n 18 0
Cigarette smoking, n (%)
 Never 870 (56.5) 743 (55.3)
 Former 278 (18.1) 244 (18.1)
 Current (any use in past 30 days) 391 (25.4) 358 (26.6)
 Missing, n 26 0
Household secondhand aerosol in past 7 days, n (%)
 None (0 days) 1015 (67.9) 882 (67.0)
 Infrequent (1–2 days) 144 (9.6) 128 (9.7)
 Frequent (≥ 3 days) 336 (22.5) 306 (23.3)
 Missing, n 70 29
Household secondhand smoke in past 7 days, n (%)
 No exposure (0 days) 876 (58.1) 758 (57.5)
 Infrequent exposure (1–2 days) 146 (9.7) 127 (9.6)
 Frequent exposure (≥ 3 days) 486 (32.2) 433 (32.9)
 Missing, n 57 27
Current wheeze, n (%)
 Yes 385 (28.1) 381 (28.3)
 Missing, n 195 0
Current asthma, n (%)
 Yes 246 (16.1) 242 (18.0)
 Missing, n 38 0
Current uncontrolled asthma symptoms, n (%)
 Yes 227 (16.6) 225 (16.7)
 Missing, n 195 0
  1. * Refers to a sample of participants with complete information on status of electronic cigarettes use, cigarette smoking, current wheeze, current asthma, and current uncontrolled asthma symptoms (i.e., excluding 220 participants with incomplete information)