Table 2

Relative risk of rheumatoid arthritis by smoking status, intensity, duration and pack-years of cigarette smoking among (ever smokers) in the Swedish Mammography Cohort, 2003 to 2010

Person-years1

Cases, number1

Age-adjusted relative risk

95% CI

Multivariable relative risk3

95% CI


Smoking status

Never

137,162

79

1.00 (ref)

1.00 (ref)

Former

59,466

60

1.65

1.17, 2.32

1.68

1.19, 2.38

Current

58,368

80

2.24

1.63, 3.07

2.20

1.58, 3.04

Intensity, cigarettes/day2

Never

137,162

79

1.00 (ref)

1.00 (ref)

1 to 7

34,032

47

2.23

1.54, 3.21

2.31

1.59, 3.36

8 to 14

32,010

45

2.23

1.54, 3.24

2.19

1.50, 3.21

> 14 (median 18)

35,586

33

1.45

0.96, 2.20

1.46

0.96, 2.23

Duration, years

Never

137,162

79

1.00 (ref)

1.00 (ref)

1 to 25

39,634

39

1.55

1.05, 2.30

1.60

1.07, 2.38

25 to 40

53,219

68

2.01

1.43, 2.83

1.99

1.40, 2.82

> 40 (median 45)

23,528

32

2.36

1.55, 3.58

2.33

1.52, 3.57

Pack-years

Never

137,162

79

1.00 (ref)

1.00 (ref)

1 to 5

27,534

28

1.67

1.08, 2.58

1.72

1.11, 2.67

6 to 13

30,613

40

2.13

1.45, 3.13

2.19

1.48, 3.25

14 to 22

36,990

35

2.10

1.40, 3.14

2.04

1.35, 3.09

> 22 (median 28)

27,628

31

1.81

1.19, 2.76

1.82

1.19, 2.79


1Numbers do not add up to the totals because of missing values; 2lifetime average among ever smokers; 3Adjusted for age (continuous), menopause status (pre- or postmenopausal), parity (0, 1, 2, or ≥ 3 children), alcohol use (none, former, or current), educational level (lower than high school, high school, or university), and body mass index (quartiles). Intensity, duration and pack-years were not mutually adjusted [35]. Ref, reference group.

Di Giuseppe et al. Arthritis Research & Therapy 2013 15:R56   doi:10.1186/ar4218

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