Table 2.

Estimated Relative Risks (RRs) for a Reported Incident or Fatal Coronary Heart Disease Death (CHD) by Pack-Years With Never Cigarette Smokers as Referent and the Fitted Excess Relative Risk per Pack-Year (ERR/PKY) at 20 Cigarettes/day (CPD) Within Level of Smoking-Related Modifiers^a

							Summary of fitted model
		Estimated RRs by pack-years					ERR/PKY @ 20 CPDb
Modifier	Casesc	1–9	10–19	20–39	40–59	≥60	Estimate	95% CI	p d
	AHS cohort
Age started smoking
<15	282	1.24	1.28	1.29	2.19	2.28	0.023	(0.015,0.036)	.15
15–17	761	1.14	1.13	1.39	1.78	2.14	0.017	(0.011,0.026)
18–19	663	1.14	1.26	1.54	1.88	2.10	0.022	(0.016,0.031)
20–22	378	1.24	1.53	1.67	2.24	2.39	0.028	(0.021,0.037)
≥23	371	1.46	1.74	2.06	2.00	2.32	0.031	(0.023,0.040)
Smoking cessation (y)
<2	875	1.73	2.09	2.42	2.59	2.66	0.031	(0.027,0.037)	<.01
2–24	542	1.40	1.26	1.39	1.59	1.92	0.015	(0.012,0.022)
≥25	1038	1.12	1.17	1.16	1.23	1.34	0.008	(0.006,0.012)
	ATBC cohort
Age started smoking
<15	369	1.87	2.54	2.55	2.86	2.78	0.031	(0.027,0.037)	.01
15–17	1611	1.71	2.16	2.27	2.35	2.83	0.029	(0.026,0.030)
18–19	1297	1.36	2.03	2.04	2.33	2.51	0.024	(0.022,0.027)
20–22	1757	1.51	2.07	2.05	2.27	2.53	0.025	(0.023,0.028)
≥23	945	1.59	1.92	1.99	2.26	2.25	0.024	(0.021,0.028)
Smoking cessation (y)e
<1	1556	1.48	1.93	1.81	1.85	2.22	0.021	(0.019,0.023)	.03
≥1	135	0.89	1.55	1.53	1.36	2.03	0.012	(0.007,0.021)

CI = confidence interval. Data from the AHS and the Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Study.

^aAHS models adjusted for center, race, birth year, age, sex, education, alcohol consumption, high blood pressure, diabetes mellitus, total cholesterol, body mass index and use of cigars or pipe exclusively with entries based on M = 5 imputations. For AHS, categories reflected one imputation. RRs computed relative to never-smokers. For ATBC, CHD rates in never-smokers derived from the CHD mortality rate in Finnish males, assuming a 0.7 proportion of ever-smokers and a RR by ever smoked of 2.0.

^bFor continuous pack-years (d) and cigarettes/day (n) with categorical modifying factor x with F levels, data fitted using: $\text{ERR} (d,n,x)={{{\displaystyle \sum }}^{\text{}}}_f {\beta }_f d_f \text{exp}\{{\gamma }_f \text{ln}(n_f)\},$ with ERR/PKY estimate at 20 cigarettes/day given as $\text{ERR} (d=1,n=20,x=x_f)={\beta }_f \text{exp}\{{\gamma }_f \text{ln}(20)\}.$ For overall data, the ERR/PKY at 20 cigarettes/day was 0.025 (0.021, 0.029) for AHS data based on parameter estimates β = 0.177 and γ = −0.659 and 0.026 (0.025, 0.027) for ATBC data based on parameter estimates β = 0.169 and γ = −0.624.

^cCHD events in smokers only.

^d p value for test of homogeneity of smoking effects across factor f, ie, β₁ =…= β_F and γ₁ =…= γ_F.

^eData restricted to the active follow-up period through 1994.