1.50 (95% CI: 1.02, 2.22; 240 cases) (Table 3), and the OR for men with high cumulative exposure and high radon was 1.58 (95% CI: 1.06, 2.36; 222 cases) (Table 4). ORs for joint exposure to high radon and frequent or high cumulative incense use were increased when incense use was classified according to quartiles (Table 3 and 4), but power was limited, and none of the synergy indices were statistically significant (data not shown).
Separate analyses for major histological types of lung cancer did not show evidence of heterogeneity among subtypes, although power to evaluate differences was limited, particularly for large-cell carcinoma (total of 25 cases).