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. Author manuscript; available in PMC: 2017 Aug 16.
Published in final edited form as: Lung Cancer. 2011 Dec 9;76(2):150–158. doi: 10.1016/j.lungcan.2011.10.014

Table 2.

Results of main and subgroup analyses for the association of parity and lung cancer risk.

Comparison Number of
studies		 Heterogeneity
(pQ; I2)		 OR (95% CI); p-value
All studies 16 <0.001; 73% 0.98 (0.95–1.02); 0.31
Study design
 Case-control 11 <0.001; 73% 0.99 (0.94–1.04); 0.69
 Cohort studies 5 0.001; 78% 0.97 (0.92–1.03); 0.36
Ethnicity
 Non-East Asian 8 <0.001; 83% 0.99 (0.93–1.06); 0.06
 East Asians 7 0.04; 54% 0.97 (0.93–1.01); 0.13
Histology
 Did not report including SCLC 8 0.002; 69% 0.94 (0.88–1.00); 0.06
 Included SCLC 7 0.33; 13% 1.00 (0.98–1.03); 0.72
Histological confirmation
available for ≥80%
 No/ NR 6 <0.001; 81% 0.97 (0.89–1.06); 0.49
 Yes 10 <0.001; 69% 0.99 (0.95–1.03); 0.58
Details on parity modeling
 No/ unclear 8 <0.001; 72% 1.00 (0.94–1.06); 0.91
 Yes 8 <0.001; 77% 0.97 (0.92–1.02); 0.27
Adjustment for smoking
 No 3 0.15; 47% 1.00 (0.92–1.09); 0.98
 Yes 13 <0.001; 77% 0.98 (0.94–1.02); 0.29
Adjustment for age
 No 1 NA 1.00 (0.96–1.03); 0.87
 Yes 15 <0.001; 75% 0.98 (0.94–1.02); 0.37

CI = confidence interval; NA = not applicable; NR = not reported; OR = odds ratio; SCLC = small-cell lung cancer. For some subgroups, the number of studies does not add up to 16 when studies did not report relevant information.