Table 5. Effect modification by radiation-exposure status on the association between non-radiation factors and thyroid cancer risk.

Variable	Non-exposed to radiation§			Exposed to radiation¶
	Case	Control	OR (95% CI)	Case	Control	OR (95% CI)
History of goiter/nodule*
No	280	304	1.00 (reference)	52	56	1.00 (reference)
Yes	25	1	25.9 (3.47-192.9)	5	1	3.75 (0.41-34.3)
			p for effect modification = 0.20
Family history of cancer*
No	235	255	1.00 (reference)	34	39	1.00 (reference)
Yes	70	50	1.55 (1.02-2.37)	23	18	1.43 (0.63-3.26)
			p for effect modification = 0.70
Smoking†
Never	244	226	1.00 (reference)	48	45	1.00 (reference)
Ever	61	79	0.57 (0.34-0.94)	9	12	0.45 (0.12-1.66)
			p for effect modification = 0.99
Alcohol drinking‡
Never	146	111	1.00 (reference)	26	30	1.00 (reference)
Ever	159	194	0.62 (0.43-0.89)	31	27	1.46 (0.62-3.42)
			p for effect modification = 0.08

Matched on city, age, sex, and radiation dose; adjusted for history of goiter or nodule and family history of cancer; and additionally adjusted tor ^†alcohol drinking (never, ever), ^‡cigarette smoking (never, ever), or *both.

§ : “Non-exposed” corresponds to “born after bombing” or “not exposed or negligible dose” of “atomic-bomb exposure” in Table 1

¶ : “exposed” corresponds to the other categories in Table 1.

OR: odds ratio

CI : confidence interval