Table 5. Test of heterogeneity in dose response and its modification by time since exposure and age at exposure in various categories of circulatory disease and cancer.

The background model for each circulatory disease subtype is a quartic model in age, with adjustment for gender, smoking habit and quantity, alcohol habit and quantity, and calendar year period treated (year of entry). Unless otherwise stated heart dose is used for all circulatory disease endpoints.

Panel	Model	p-value
A	Test of heterogeneity across four circulatory disease endpoints (using heart dose throughout), linear dose response
	Background[1+ a D exp[δ (time since exposure - 20.78)]]a	<0.001b
	Background[1+ ai D exp[δ (time since exposure - 20.78)]]a	0.283c
	Background[1+ ai D exp[δi (time since exposure - 20.78)]]a	0.372d
B	Test of heterogeneity across four circulatory disease endpoints (using thyroid dose for stroke, heart dose otherwise), linear dose response
	Background[1+ a D exp[δ (time since exposure - 20.78)]]a	<0.001b
	Background[1+ ai D exp[δ (time since exposure - 20.78)]]a	0.011c
	Background[1+ ai D exp[δi (time since exposure - 20.78)]]a	0.370d

^atime since exposure is approximately centered by subtracting off its person-year weighted mean (20.78 years) in the full cohort (exposed+unexposed), to stabilize parameter estimates.

^bp-value for improvement of fit over model without radiation dose response term.

^cp-value for improvement of fit over model with the same excess relative risk coefficient (α) for each endpoint.

^dp-value for improvement of fit over model with the same time trend in excess relative risk (δ) for each endpoint.