Dose-response relationship of lung cancer to amount smoked, duration and age starting

Table 6 Amount smoked by current smokers - inverse-variance weighted simple regression analyses of β₁ based on best-fitting log + baseline model

Factor	Level	n	β1 (95% CI)	P1	RR for 20 cigs/d
All		97	0.83 (0.80-0.86)		10.71
Sex	Male	55	0.79 (0.75-0.84)	< 0.05	9.50
	Female	34	0.82 (0.75-0.88)		10.21
	Combined	8	0.89 (0.84-0.94)		12.50
Study type	Case-control	49	0.86 (0.82-0.90)	< 0.1	11.48
	Prospective	48	0.80 (0.76-0.85)		9.85
Continent	North America	43	0.87 (0.84-0.89)	< 0.001	11.48
	Europe	32	0.83 (0.76-0.90)		10.65
	Asia	17	0.53 (0.45-0.61)		4.53
	Other	5	0.80 (0.61-0.99)		9.80
Publication year2	< 1990	40	0.83 (0.79-0.88)	< 0.1	10.71
	1990-1994	29	0.77 (0.70-0.84)		8.90
	1995-1999	28	0.87 (0.82-0.92)		11.94
Product3	Any product	20	0.75 (0.64-0.85)	NS	8.36
	Cigarettes +/-	61	0.85 (0.81-0.88)		11.09
	Cigarettes only	16	0.82 (0.74-0.90)		10.19
Unexposed	Never cigarettes	32	0.83 (0.76-0.90)	NS	10.49
	Never any product	65	0.84 (0.80-0.87)		10.76
Grouped midpoint age (yr)	< 50	14	0.79 (0.67-0.92)	< 0.1	9.57
	50-59	62	0.85 (0.82-0.89)		11.35
	60+	21	0.79 (0.71-0.84)		9.13
Cases in smokers	< 100	29	0.67 (0.56-0.78)	< 0.001	6.72
	100 to < 200	28	0.73 (0.64-0.83)		8.08
	200 to < 500	16	0.76 (0.65-0.87)		8.72
	500 to < 1000	16	0.80 (0.75-0.86)		9.87
	1000+	8	0.89 (0.85-0.92)		12.42

¹Probability values for factor considered, presented as < 0.001, < 0.01, < 0.05, < 0.1 or not significant (NS) (P≥ 0.1);

²Of principal publication for the study;

³Any product = Smokes cigarettes and/or pipes and/or cigars; Cigarettes +/- = Smokes cigarettes with or without other products (pipes, cigars).