Table 4.

Hazard Ratios for Year From Cox Regression Involving Duration of Symptoms, Intake Group and Year, and the Interaction Between Intake Group and Year

			Estimated Hazard Ratio	95% Confidence Interval	P Value
yr1	AT		0.63	0.45, 0.88	.006
	Non-AT		1.00	0.78, 1.28	.966
yr2	AT	97–98 vs 95–96	0.58	0.15, 2.26	.433
		99–00 vs 95–96	0.07	0.01, 0.53	.011
	Non-AT	97–98 vs 95–96	0.94	0.42, 1.85	.742
		99–00 vs 95–96	1.29	0.50, 3.33	.598
yr3	AT	98–00 vs 95–97	0.10	0.02, 0.46	.003
	Non-AT	98–00 vs 95–97	1.23	0.60, 2.54	.570