Table 1

Characteristics of studies reviewed

StudyCountrySample size,
N
Diabetes, N (%)Hypertension, N (%)CVD, N (%)Pulmonary disease, N (%)Active smokers, N (%)Former
smokers, N (%)
ICU admission, N (%)Mortality, N (%)Notes
Original studies
Huang et al 14
China418 (19.5)6 (14.6)6 (14.6)1 (2.4)3 (7.3)NR7 (17.1)6 (14.6)
Guan et al 15
China108581 (7.5)165 (15.2)27 (2.5)12 (1.1)137 (12.6)21 (1.9)55 (5.0)15 (1.4)
Zhang et al 16
China14017 (12.1)42 (30.0)12 (8.6)2 (1.4)2 (1.4)7 (5.0)
Yang
et al 17
China529 (17.3)5 (9.6)4 (7.7)2 (3.8)NR52 (100.0)32 (61.5)
Mo et al 18
China15515 (9.7)37 (21.9)15 (9.7)5 (3.2)6 (3.9)NR
Zhou et al 19
China19136 (18.9)58 (30.4)15 (7.9)6 (3.1)11 (5.8)NR50 (26.2)54 (28.3)
Guo et al 20
China18728 (14.9)61 (32.6)21 (11.2)18 (9.6)NR43 (23.0)
Richardson et al 28
USA35671808 (50.7)3026 (84.8)966 (27.1)920 (25.8)558 (15.6)NR1281 (22.5)553 (9.7)
Goyal et al 26
USA39399 (25.2)197 (50.1)82 (20.9)69 (17.6)20 (5.1)NR40 (10.2)
Qin et al 21
China45275 (16.6)135 (29.9)27 (5.9)12 (2.7)7 (1.5)NR
Cummings et al 27
USA25792 (35.8)162 (63.0)49 (19.1)24 (9.3)33 (12.8)*NR203 (79.0)101 (39.3)
Meta-analyses
Farsalinos et al 22
China5960450 (7.6)35 (0.6)Pooled prevalence of smokers among hospitalised patients with COVID-19 in China was 6.5% (95% CI 4.9% to 8.2%)
Lippi et al 40
China1399No significant association between active smoking and COVID-19 severity (OR 1.69 (0.41 to 6.92); p=0.254)
Preprints
Miyara et al 24
France482102/473158/47329/47334/473285/473Daily smokers have lower probability of developing severe COVID-19 when compared with the general population
OpenSAFELY Collaborators31
UK17 425 455489 297 (2.8)5 962 122 (34.2)1 173 433 (6.7)707 284 (4.1)2 962 373 (17.0)5 737 545 (32.9)5683 (0.03)On adjustment for multiple covariates, smoking was associated with a reduced risk for COVID-19 mortality (OR 0.88 (0.79 to 0.99))
  • *Study reported ‘current or former smokers’.

  • CI, Confidence interval; CVD, cardiovascular disease; ICU, Intensive care unit; NR, not reported; OR, Odds ratio; UK, United Kingdom; USA, United States of America.