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

Table 11 Duration of smoking by current smokers - inverse-variance weighted simple regression analyses of β₁ based on best-fitting power model

Factor	Level	n	β1 (95%CI)	P1	RR for 30 yr smoked
All		35	0.79 (0.72-0.86)		5.94
Sex	Male	18	0.84 (0.73-0.94)	NS	6.59
	Female	15	0.74 (0.64-0.85)		5.35
	Combined	2	0.79 (0.45-1.12)		5.89
Study type	Case-control	7	0.73 (0.50-0.97)	NS	5.24
	Prospective	28	0.80 (0.72-0.87)		6.02
Continent	North America	27	0.81 (0.73-0.88)	NS	6.19
	Europe	5	0.55 (0.20-0.90)		3.44
	Asia	1	0.51 (-0.11-1.13)		3.15
	Other	2	0.73 (0.19-1.27)		5.15
Publication year2	< 1990	8	0.76 (0.52-0.99)	NS	5.50
	1990-1994	2	0.44 (-0.20-1.09)		2.73
	1995-1999	25	0.80 (0.72-0.88)		6.08
Product3	Any product	4	0.50 (0.18-0.83)	NS	3.12
	Cigarettes +/-	10	0.86 (0.73-0.98)		6.89
	Cigarettes only	21	0.78 (0.70-0.87)		5.85
Unexposed	Never cigarettes	19	0.77 (0.69-0.86)	NS	5.71
	Never any product	16	0.85 (0.71-0.99)		6.75
Grouped midpoint age (yr)	< 50	8	1.06 (0.78-1.34)	< 0.05	11.00
	50-59	13	0.87 (0.75-0.99)		7.04
	60+	14	0.73 (0.65-0.82)		5.21
Cases in smokers	< 100	14	0.62 (0.39-0.84)	NS	4.01
	100 to < 200	9	0.73 (0.59-0.87)		5.19
	200 to < 500	6	0.78 (0.67-0.89)		5.18
	500 to < 1000	5	0.95 (0.80-1.10)		8.58
	1000+	1	0.80 (0.59-1.01)		6.04

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).