Table 2.

Radiation Dose and Population Density Associations With Risk of Solid Cancer Mortality Among 86,660 Atomic Bomb Survivors With Known Radiation Doses^a, Life Span Study, Hiroshima and Nagasaki, Japan, 1950–2003

Model	Radiation Dose		Population Density		AIC
	ERRb	95% CI	RRc	95% CI
Based	0.448	0.340, 0.557			43,714.5
With density	0.425	0.315, 0.535	1.018	0.998, 1.039	43,713.3
With density × age	0.428	0.318, 0.538			43,711.6
<10 years			1.002e	0.945, 1.062
10–14 years			1.069e	1.025, 1.115
15–29 years			1.031e	0.999, 1.064
≥30 years			1.009e	0.985, 1.033

Abbreviations: AIC, Akaike information criterion; CI, confidence interval; ERR, excess relative risk; RR, relative risk.

^a The Dosimetry System 2002 (1, 2) method was used to estimate Dosimetry System 2002 Revision 1 (DS02R1)-weighted absorbed colon doses.

^b Sex-averaged ERR of solid cancer mortality per gray increase in weighted absorbed colon dose, among those exposed to a radiation dose with a total shielded kinetic energy released per unit mass of ≤4 gray at age 30 years and who achieved an attained age of 70 years.

^c Relative risk of solid cancer mortality per 5,000-people/km² increase in population density.

^d Base model adjusted for city, distance >5 km, sex, age at exposure, and attained age as well as effect modification by sex, age at exposure, attained age, and total shielded kinetic energy released per unit mass of >4 gray.

^e Likelihood ratio P value for evaluating the null hypothesis of equality in relative risks across age groups (3 degrees of freedom): P = 0.052.