The relation between smokeless tobacco and cancer in Northern Europe and North America. A commentary on differences between the conclusions reached by two recent reviews

Table 5 Comparison of individual and overall (random-effects) estimates for the two reviews – lung cancer

	ST use^a
Ref	Type	Exposure	Inclusion of smokers^b	Review^c	Sex	Relative risk (95% CI)	Comments
[31]	ST	Ever	NS	L&H	F	6.80 (1.60–28.5)	Not included by B
[3]	ST	Current	NS	L&H	M	1.08 (0.64–1.83)
(CPS-I)	ST	Current	NS	B	M	1.1 (0.6–1.8)	Estimates agree^d
[3]	ST	Ever	NS	L&H	M	1.77 (1.14–2.74)^e
(CPS-II)	ST	Current	NS	B	M	2.0 (1.2–3.2)	Current not ever exposure
[4]	Snuff	Ever	SNS	L&H	M	0.80 (0.61–1.05)	Estimate for NS also available
	Snuff	Ever	SNS	B	M	0.8 (0.6–1.1)	Estimates agree^d
[5]	Snuff	Ever	SNS	L&H	M	0.7 (0.6–0.7)
	Snuff	Ever	NS	B	M	0.8 (0.5–1.3)	NS not SNS
[27]	ST	Ever	SNS	L&H	M	0.69 (0.47–1.00)^e	Not included by B
Total				L&H		0.99 (0.71–1.37)	6 estimates
				B		1.2 (0.7–1.9)	5 estimates^f

^a ST = smokeless tobacco; ever exposure includes undefined use.
^b NS = never smokers; SNS = smokers and nonsmokers combined (with adjustment for smoking).
^c L&H = Lee and Hamling review [2]; B = Boffetta et al. review [1].
^d To within rounding error, as B only expressed estimates to one decimal place.
^e Estimated from data provided.
^f B only presented four estimates, but a combined result stated to be based on five. The random-effects estimate for the four estimates provided is 1.1 (0.7–1.6)

ISSN: 1471-2407