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Table 4 FEV1 decline (in mL/yr) by smoking groupa

From: Systematic review of the evidence relating FEV1decline to giving up smoking

  

Never smokersb

(95% CI)

Ex-smokersc

(95% CI)

Quittersd

(95% CI)

Continuing smokerse

(95% CI)

Unweighted analysisf

     

Number of betas

 

80

66

64

85

Unadjusted

Mean

27.9 (23.5-32.4)

24.1 (19.2-29.1)

33.4 (28.4-38.4)

42.8 (38.5-47.2)

 

Diff 1

-14.9***

-18.7***

-9.4**

Base

 

Diff 2

Base

-3.8NS

+5.5NS

+14.9***

Adjusted for age and sex

Mean

28.8 (25.0-32.7)

24.6(20.3-28.8)

33.0 (28.7-37.3)

41.9 (38.2-45.6)

 

Diff 1

-13.1***

-17.4***

-8.9**

Base

 

Diff 2

Base

-4.3NS

+4.2NS

+13.1***

Adjusted for blockg

     

(fixed-effects model)

Mean

28.7 (26.4-30.9)

27.0 (24.5-29.5)

30.4 (27.9-33.0)

42.1 (40.0-44.3)

 

Diff 1

-13.5***

-15.2***

-11.7***

Base

 

Diff 2

Base

-1.7NS

+1.7NS

+13.5***

(random-effects model)

Mean

28.6 (24.4-32.9)

26.6 (22.2-31.0)

30.6 (26.2-35.1)

42.2 (38.0-46.4)

 

Diff 1

-13.6***

-15.6***

-11.6***

Base

 

Diff 2

Base

-2.1NS

+2.0NS

+13.6***

Weighted analysish

     

Number of betas

 

71

57

56

77

Unadjusted

Mean

26.1 (23.9-28.3)

29.3 (25.6-32.9)

38.3 (33.5-43.2)

41.8 (39.1-44.6)

 

Diff 1

-15.7***

-12.6***

-3.5NS

Base

 

Diff 2

Base

+3.1NS

+12.2***

+15.7***

Adjusted for age and sex

Mean

28.9 (27.0-30.9)

27.9 (24.8-30.9)

34.2 (30.1-38.4)

39.5 (37.2-41.9)

 

Diff 1

-10.6***

-11.6***

-5.3*

Base

 

Diff 2

Base

-1.1NS

+5.3*

+10.6***

Adjusted for blockg

     

(fixed-effects model)

Mean

29.2 (28.1-30.4)

27.6 (25.9-29.4)

31.6 (29.1-34.1)

40.1 (38.6-41.5)

 

Diff 1

-10.8***

-12.4***

-8.5***

Base

 

Diff 2

Base

-1.6NS

+2.4NS

+10.8***

(random-effects model)

Mean

29.6 (25.6-33.5)

28.0 (23.9-32.1)

32.2 (27.8-36.7)

40.8 (36.9-44.8)

 

Diff 1

-11.3***

-12.8***

-8.6***

Base

 

Diff 2

Base

-1.5NS

+2.7NS

+11.3***

  1. aBased on data in Table 3. The table shows the mean forced expiratory volume in 1 second (FEV1) decline in millilitres per year in the four smoking groups with 95% confidence interval (95% CI) and also the mean differences from continuing smokers (Diff 1) and from never smokers (Diff 2), with statistical significance indicated. ***P < 0.001, **P < 0.01, *P < 0.05 and NS P ≥ 0.05. bNever smoked by end of follow-up. cGave up smoking before baseline and did not resume smoking. dSmoked at baseline, but not at end of follow-up. eSmoked at baseline and at end of follow-up. fUsing all estimates in Table 3 except the 8 estimates for ages 25-74 for study 29. gA block is a row in Table 3 consisting of a set of results for the same study and stratifying variables. hUsing all estimates in Table 3, except the 40 estimates in study 29 and the 2 estimates in study 45 without SEs.