Duration of quitting | Statisticb
| All lung cancerc
| Squamousd
| Adenoe
|
|---|
Number of setsf
| | 58 | 11 | 11 |
About 3 yearsg
| n | 41 | 6 | 6 |
| | F | 0.98 (0.93-1.04) | 1.15 (1.03-1.28) | 1.02 (0.85-1.22) |
| | R | 0.95 (0.84-1.08) | 1.15 (1.03-1.28) | 1.02 (0.85-1.22) |
| | H, PH
| 3.55 p < 0.001 | 0.51, NS | 0.74, NS |
About 7 yearsh
| n | 29 | 4 | 4 |
| | F | 0.60 (0.56-0.64) | 0.74 (0.65-0.85) | 0.73 (0.58-0.92) |
| | R | 0.57 (0.50-0.64) | 0.74 (0.65-0.85) | 0.73 (0.58-0.92) |
| | H, PH
| 2.09, p < 0.001 | 0.09, NS | 0.59, NS |
About 12 yearsi
| n | 48 | 9 | 9 |
| | F | 0.32 (0.30-0.34) | 0.40 (0.35-0.47) | 0.50 (0.41-0.60) |
| | R | 0.28 (0.24-0.32) | 0.27 (0.18-0.40) | 0.39 (0.26-0.58) |
| | H, PH
| 4.22, p < 0.001 | 4.07, p < 0.001 | 3.68, p < 0.001 |
Longest vs. shortestj
| n | 61 | 12 | 12 |
| | F | 0.23 (0.21-0.25) | 0.19 (0.16-0.22) | 0.30 (0.23-0.37) |
| | R | 0.24 (0.20-0.29) | 0.14 (0.08-0.25) | 0.21 (0.10-0.46) |
| | H, PH
| 5.21, p < 0.001 | 6.68 p < 0.001 | 9.44, p < 0.001 |
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a Within each study, results for ex smokers are selected in the following preference order, within each sex, for:
- smoking product – any, cigarettes (ignoring other products), cigarettes only;
- cigarette type – any, manufactured (with or without handrolled), manufactured only;
- adjustment for other aspects of smoking – least available;
- comparison group – current smokers, current and recent smokers (up to 2 years);
- follow-up period – longest available;
- lung cancer type – see notes c to e;
- race – all or nearest available, otherwise by race;
- overlapping studies – principal, subsidiary;
- age – whole study, widest available age group;
- Results are then selected for:
- sex –- single sex results, combined sex results;
- adjustment for potential confounders – most available.
-
b n = number of estimates combined, F = fixed-effect meta-analysis RR (95% CI), R = random-effects meta-analysis RR (95% CI), H = heterogeneity chisquared per degree of freedom, PH = probability value for heterogeneity expressed as p < 0.001, p < 0.05, p < 0.1 or NS (p ≥ 0.1).
-
c All or nearest available, must include at least squamous cell carcinoma and adenocarcinoma.
-
d Squamous cell carcinoma or nearest available, but not including adenocarcinoma.
-
e Adenocarcinoma or nearest available, but not including squamous cell carcinoma.
-
f Number of sets of RRs available for the key value analysis, where base for comparison is never smoked.
-
g Category for which results are provided includes 3 years but does not include 7 years.
-
h Category for which results are provided includes 7 years but does not include 3 or 12 years.
-
i Category for which results are provided includes 12 years but does not include 7 years.
-
j For this analysis only, the exposed and unexposed group have the same smoking status (i.e. ex-smokers), product and cigarette type. There is a preference (instead of that for comparison group) to select the results for the longest (=exposed) and shortest (=unexposed) duration quitters. Note that (unlike the inverse results shown in Table 18), the “shortest” quitters here may omit recent quitters, but subject to a limit of no more than two years.
