Table 4
Cumulative effect of smoking on occurrence of pulmonary tuberculosis
Smoking duration (years)
<10
11–20
>20
Non-smokers
p<0.0001 (χ
2
for linear trend = 15.867).
Cases
14
22
28
21
Controls
80
88
85
206
Odds ratio
1.72
2.45
3.23
–