Table 2:

Effects of climate, patient demographics, and hospital characteristics on the incidence of SAH and SAH-related mortality

Variable	SAH Incidence Model (χ² = 3483, df = 20, P < .0001)		SAH Death Model (χ² = 896, df = 20, P < .0001)
Variable	RR^b	P value	RR^b	P value
Temperature stratum (df = 6)^c	see Figure 3A	.1453	see Figure 3B	.3005
USDA zone (df = 8)^c	see Figure 3c^a	.0009^a	see Figure 3D	.0863
Age (df = 1)^d	0.99 (0.98–1.01)	.5787	1.18 (1.16–1.19)^a	<.0001^a
Female gender (df = 1)^e	1.03 (1.01–1.06)^a	.0375^a	1.01 (0.98–1.03)	.5579
Teaching hospitals (df = 1)^f	1.25 (1.20–1.32)^a	<.0001^a	0.90 (0.85–0.97)^a	<.0001^a
Large hospital bed size (df = 1)^g	1.07 (1.02–1.11)^a	.0017^a	0.99 (0.94–1.01)	.1124
Urban location (df = 1)^h	1.09 (1.04–1.15)^a	.0003^a	0.97 (0.92–1.02)	.1358

↵a Indicates significant effects.
↵b RR with 95% confidence interval as defined in Materials and Methods.
↵c See Materials and Methods for a description of stratifications and groupings.
↵d Change in RR for every 10-year increase in age.
↵e Compared to males.
↵f Compared with nonteaching hospitals.
↵g Compared with small and medium-sized hospitals.
↵h Compared with rural hospital locations.