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Table 1 The equivalents of pack-years of tobacco smoke and exposure years to biomass smoke*

From: Risk of acute exacerbations in chronic obstructive pulmonary disease associated with biomass smoke compared with tobacco smoke

 

If biomass smoke < n years

If tobacco smoke < m pack-years

Tobacco smoke (m), pack-years

Exposure to biomass smoke (n), years

B4

SE

β

P value

\( {\mathrm{B}}_5^{\prime } \)

SE

β′

P value

10

10

−4.22

1.79

−0.12

0.019

−0.15

1.87

−0.01

0.937

15

−3.48

1.48

−0.10

0.019

0.37

1.83

0.02

0.840

20

−3.51

1.44

−0.11

0.015

−0.14

1.83

−0.01

0.941

25

−4.20

1.32

−0.13

0.002

−3.83

1.92

−0.14

0.048

30

−4.12

1.30

−0.13

0.002

−2.24

2.00

−0.08

0.263

20

10

−4.36

1.43

−0.15

0.003

0.51

1.59

0.02

0.749

15

−3.60

1.24

−0.13

0.004

0.74

1.58

0.03

0.639

20

−3.62

1.21

−0.13

0.003

0.38

1.60

0.02

0.811

25

−4.39

1.11

−0.15

< 0.001

−3.25

1.68

−0.12

0.054

30

−4.01

1.09

−0.14

< 0.001

−1.38

1.73

−0.05

0.424

  1. *Multiple linear regression adjusting for age (< 60 vs. ≥60 years), sex, and height (cm). The standardized regression coefficient of B4 (β) and that of \( {\mathrm{B}}_5^{\prime } \) (β′) were most similar when m was 10 and n was 25 (β = − 0.13 and β′ = − 0.14)
  2. B4 unstandardized regression coefficient for tobacco smoke, \( {B}_5^{\prime } \) unstandardized regression coefficient for biomass smoke, β standardized regression coefficient of B4, β′ standardized regression coefficient of \( {\mathrm{B}}_5^{\prime } \), SE standard error