Table 5.

Pooled Risk Estimates for Lung Cancer Associated With Soy/Isoflavone Intake in Subgroup Meta-Analysis

Factor	No. of Studies	Relative Riska	95% Confidence Interval	I2, %b	Test for Heterogeneityc		Pdheterogeneity
					χ2	P Value
All studies	11	0.83	0.72, 0.96	54.6	37.44	0.003
Sex							0.89
Male	6	0.80	0.61, 1.06	67.9	18.72	0.005
Female	11	0.79	0.67, 0.94	49.9	25.93	0.02
Ever smoker							0.0003
Yes	5	0.91	0.78, 1.05	38.4	9.74	0.14
No	7	0.59	0.49, 0.71	0.0	4.58	0.71
Study design							0.84
Case-control	7	0.83	0.67, 1.04	65.6	31.94	<0.001
Cohort	4	0.85	0.74, 0.97	8.4	5.46	0.36
Study population							0.71
Asian	9	0.83	0.70, 0.99	55.8	31.69	0.004
American	2	0.83	0.60, 1.14	64.3	34.69	0.06
Measure of soy intake							0.54
Soy/tofu	8	0.82	0.66, 1.01	62.0	31.55	0.002
Isoflavones	6	0.80	0.71, 0.89	29.0	11.26	0.19

^a Summary relative risks were based on the odds ratio or relative risk for the highest category of soy/isoflavone intake versus the lowest in each original study, using the DerSimonian and Laird random-effects model (34), with the exception of summary relative risks for nonsmokers and cohort studies, for which a fixed-effects model was used.

^b I² represents the percentage of total variation across studies that is attributable to heterogeneity rather than to chance (54).

^c Test for heterogeneity among studies in the category.

^d Test for heterogeneity between categories of the factor stratified.