Table 3.

Meta-analysis of tobacco and alcohol history and I² values amongst 28 studies (n = 2691).

History	Proportion % [95% CI]	I2 (%)
Current smoker	13.0 [5.9, 22.2]	87.8
Former smoker	30.6 [18.7, 44.0]	90.6
Never smoker	50.0 [43.0, 57.1]	90.2
Unknown smoking history	6.5 [3.8, 9.9]	0.0
History of <20 pack years	16.5 [6.2, 30.4]	83.8
History of ≥20 pack years	22.6 [12.7, 34.3]	80.3
History of ≤10 pack years	24.4 [17.6, 31.8]	87.1
History of >10 pack years	26.9 [19.2, 35.4]	87.8
Current drinker	46.2 [26.3, 66.8]	89.2
Former drinker	10.1 [1.5, 48.5]	95.2
Never drinker	28.7 [6.6, 58.4]	95.4