Table 14.

Meta-analyses by type of cigarette smoked^a

Type of cigarette smoked	Statisticb	All lung cancerc	Squamousd	Adenoe
Only filter vs. only plainf	n	42	13	10
	F	0.67 (0.64-0.72)	0.58 (0.52-0.64)	0.88 (0.75-1.03)
	R	0.69 (0.61-0.78)	0.52 (0.40-0.68)	0.84 (0.66-1.08)
	H, PH	3.18, p < 0.001	4.73, p < 0.001	1.90, p < 0.05
Ever filter vs. only plaing	n	42	11	10
	F	0.79 (0.75-0.83)	0.85 (0.79-0.91)	1.00 (0.89-1.12)
	R	0.73 (0.65-0.82)	0.55 (0.41-0.74)	0.99 (0.84-1.16)
	H, PH	3.60, p < 0.001	7.73, p < 0.001	1.35, NS
Only filter vs. ever plainh	n	42	13	10
	F	0.67 (0.63-0.71)	0.87 (0.81-0.92)	1.05 (0.93-1.18)
	R	0.70 (0.62-0.78)	0.69 (0.57-0.83)	0.98 (0.80-1.21)
	H, PH	3.30, p < 0.001	3.15, p < 0.001	1.88, p < 0.05
Handrolled vs. manufacturedi	n	20	5	4
	F	1.27 (1.16-1.40)	1.47 (1.24-1.76)	2.12 (1.53-2.96)
	R	1.29 (1.12-1.49)	1.62 (1.18-2.21)	2.09 (0.83-5.25)
	H, PH	1.81, p < 0.05	2.61, p < 0.05	6.54, p < 0.001
Mentholated vs. non-mentholated	n	6	1	1
	F	0.99 (0.86-1.14)	1.04 (0.75-1.44)	0.96 (0.73-1.27)
	R	0.98 (0.80-1.20)	1.04 (0.75-1.44)	0.96 (0.73-1.27)
	H, PH	1.89, p < 0.1	NA	NA

^a Within each study, results for the relevant smoking product and smoking status are selected in the following preference order, within each sex, for:

cigarette type – see notes f to i;

unexposed group – see notes f to i;

smoking product – any, cigarettes (ignoring other products), cigarettes only;

smoking status – ever, current;

lung cancer type – see notes c to e;

race – all or nearest available, otherwise by race;

follow-up period – longest available;

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.

^f Or nearest available.

Preference order for cigarette type – filter only/NOS, always, mainly, both, equally, ever.

Preference order for comparison group – plain only/NOS, always, mainly, ever.

^g Or nearest available.

Preference order for cigarette type – filter ever, equally, both, mainly, always, only/NOS.

Preference order for comparison group – plain only/NOS, always, mainly, ever.

^h Or nearest available.

Preference order for cigarette type – filter only/NOS, always, mainly, both, equally, ever.

Preference order for comparison group – plain ever, mainly, always, only/NOS.

ⁱ Preference order for cigarette type – handrolled any, both, mainly, only.

Preference order for comparison group – manufactured only ever, only current, any, ever.