Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BMC Cancer

Table 11 Main meta-analyses for current or ever smoking of any product (or cigarettes, if not available) ^a

Preference	Statistic^b	All lung cancer^c	Squamous^d	Adeno^e
Ever smoking to current smoking	n	342	110	116
	F	4.25 (4.20-4.31)	9.15 (8.63-9.70)	3.38 (3.23-3.55)
	R	5.48 (5.07-5.93)	10.58 (9.04-12.37)	2.94 (2.52-3.43)
	H, P_H	22.46, p < 0.001	5.22, p < 0.001	8.61, p < 0.001
Current smoking to ever smoking	n	344	110	116
	F	4.45 (4.39-4.51)	10.08 (9.51-10.69)	3.58 (3.41-3.76)
	R	6.20 (5.68-6.77)	11.53 (9.73-13.66)	3.13 (2.67-3.67)
	H, P_H	28.33, p < 0.001	6.30, p < 0.001	8.99, p < 0.001

^a Within each study, results are selected in the following preference order, within each sex, for:
smoking status – ever, current or current, ever according to analysis;
smoking product – any, cigarettes (ignoring other products), cigarettes only;
cigarette type – any, manufactured (with or without handrolled), manufactured only;
unexposed group – never any product, never cigarettes, near equivalent (see Methods);
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, P_H = probability value for heterogeneity expressed as p < 0.001, p < 0.05, p < 0.1 or NS (p ≥ 0.1), P_B = probability value for between levels (see Methods) similarly expressed.
^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.

ISSN: 1471-2407