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

Lee, Peter N; Forey, Barbara A; Coombs, Katharine J

doi:10.1186/1471-2407-12-385

BMC Cancer

Table 7 Meta-regression results for ever smoking of any product (or cigarettes if any product not available) ^a

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

Characteristic	Level	All lung cancer		Squamous		Adeno
		Estimate^b(SE^c)	p^d	Estimate^b(SE^c)	p^d	Estimate^b(SE^c)	p^d
Constant		+1.280 (0.052)		+1.281 (0.174)		+0.368 (0.178)
Sex	Male	Base	NS	Base	NS	Base	<0.05
	Female	−0.040 (0.016)		−0.046 (0.072)		−0.275 (0.058)
	Combined	+0.018 (0.029)		−0.130 (0.141)		+0.102 (0.138)
Location	North America	Base	<0.001	Base	<0.001	Base	<0.001
	United Kingdom	−0.108 (0.057)		−0.861 (0.266)		−0.535 (0.324)
	Scandinavia	−0.095 (0.051)		−0.484 (0.241)		−0.630 (0.190)
	Other Europe	−0.319 (0.039)		−0.609 (0.114)		−0.731 (0.107)
	China	−1.320 (0.024)		−1.028 (0.120)		−1.356 (0.094)
	Japan	−0.858 (0.053)		−0.562 (0.226)		−1.158 (0.119)
	Other Asia	−0.646 (0.060)		−0.390 (0.158)		−0.557 (0.127)
	Other or multiregion	−0.173 (0.076)		−0.031 (0.301)		−0.024 (0.213)
Start year of study	Before 1960	Base	<0.001	Base	<0.001	Base	<0.05
	1960-69	+0.384 (0.047)		+0.819 (0.154)		+0.750 (0.166)
	1970-79	+0.430 (0.045)		+0.802 (0.130)		+0.672 (0.150)
	1980-89	+0.783 (0.042)		+0.990 (0.134)		+0.857 (0.155)
	1990 or later	+0.872 (0.063)		+1.788 (0.263)		+0.892 (0.200)
Study type	Case–control	Base	<0.01	Base	NS	Base	NS
	Prospective^e	+0.238 (0.036)		+0.395 (0.233)		+0.352 (0.140)
Number of cases^f	100-249	Base	<0.001	Base	<0.05	Base	<0.05
	250-499	+0.101 (0.044)		+0.251 (0.152)		+0.265 (0.107)
	500-999	+0.293 (0.043)		+0.729 (0.162)		+0.550 (0.121)
	1000+	+0.290 (0.038)		+0.655 (0.145)		+0.594 (0.100)
Number of adjustment factors	0	Base	<0.05	Base	<0.05	Base	<0.1
	1	−0.171 (0.034)		+0.477 (0.147)		+0.391 (0.110)
	2+	+0.017 (0.025)		−0.226 (0.097)		+0.272 (0.078)

^a Based on the same data as for Table 5. See that table for further definition of RRs selected for analysis, and numbers of estimates of each characteristic level.
^b Estimates are of log RR. The predicted RR of a given estimate can be calculated by adding the constant to the values for the level of each characteristic applicable to the estimate (taking the value for a base level as zero) and taking the exponential of the result.
^c SE = standard error.
^d The p value is estimated from the drop in deviance from removing the characteristic from the fixed model using an F-test. It is expressed as p < 0.001, p < 0.01, p < 0.05, p < 0.1 or NS (p ≥ 0.1).
^e Or nested case–control or case-cohort in the case of 5 estimates for all lung cancer, 4 for squamous and 4 for adeno.
^f In the study as a whole.
Note For the forward stepwise analyses, deviances, degrees of freedom and p values for inclusion in order of inclusion are as follows:
All lung cancer: Constant 7470.075 on 327 d.f. (p < 0.001), location 2247.358 on 320 d.f. (p < 0.001), start year of study 1599.339 on 316 d.f. (p < 0.001), number of cases 1523.722 on 313 d.f. (p < 0.01), study type 1497.854 on 312 d.f. (p < 0.05) and number of adjustment variables 1463.482 on 310 d.f. (p < 0.05). Fixed model deviance 1454.810 on 308 d.f.
Squamous: Constant 522.221 on 101 d.f. (p < 0.001), start year of study 419.586 on 97 d.f. (p < 0.001) and location 308.715 on 90 d.f. (p < 0.001). Fixed model deviance 260.432 on 82 d.f.
Adeno: Constant 930.356 on 106 d.f. (p < 0.001), location 431.955 on 99 d.f. (p < 0.001), number of cases 369.648 on 96 d.f. (p <0.01), start year of study 328.896 on 92 d.f. (p < 0.05) and sex 307.336 on 90 d.f. (p < 0.05). Fixed model deviance 284.147 on 87 d.f.

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