Spatial variation in hyperthermia emergency department visits among those with employer-based insurance in the United States – a case-crossover analysis

Table 2 Regression results for time-stratified case-crossover analyses (pooled data 2000–2010)

	Model A		Model B		Model C		Model D
	OR	95% CI	OR	95% CI	OR	95% CI	OR	95% CI
Maximum temperature °F	1.15	1.14, 1.16	1.15	1.14, 1.16	1.15	1.14, 1.17	1.16	1.15, 1.17
Heat wave indicator^a			1.13	0.96, 1.33	1.14	0.84, 1.55	1.15	0.84, 1.54
PM_2.5 concentration (g/m³)					1.02	1.01, 1.03
Ozone concentration (ppb)					0.99	0.98, 1.01
Holiday indicator^b					1.23	0.82, 1.88
Model AIC	14833		14830		4972		4983
Cases	11031		11031		3756		3756
Control days	13774		13774		4655		4655
Maximum heat index	1.12	1.11, 1.21	1.11	1.11, 1.12	1.11	1.10, 1.12	1.12	1.11, 1.13
Heat wave indicator^a			1.46	1.26, 1.70	1.47	1.09, 1.98	1.58	1.17, 2.12
PM_2.5 concentration (g/m³)					1.01	1.01, 1.02
Ozone concentration (ppb)					1.01	1.00, 1.01
Holiday indicator					1.25	0.82, 1.90
Model AIC	14902		14879		4962		5007
Cases	11031		11031		3756		3756
Control days	13774		13774		4655		4655
Spatial synoptic classification	2.56	2.39, 2.74	2.14	1.89, 2.43	1.68	1.36, 2.08	1.99	1.61, 2.45
Heat wave indicator^c			1.25	1.09, 1.44	1.32	1.04, 1.65	1.32	1.05, 1.67
PM_2.5 concentration (g/m³)					1.03	1.02, 1.04
Ozone concentration (ppb)					1.01	1.01, 1.02
Holiday indicator					1.27	0.85, 1.91
Model AIC	14996		14986		5349		5621
Cases	9978		9978		3672		3672
Control days	12442		12442		4537		4537

Maximum daily temperature, maximum daily heat index and SSC correspond to day of ED visit (day₀). Model B indicates if there is an additional ‘heat wave’ duration effect. Since PM_2.5 and Ozone concentrations are not available for all days, the sample sizes for Models C & D are smaller. Comparison of Models B & D indicate if the restricted sample used in Model D (observations with air pollution variables) produce different effect estimate than those obtained using the full sample in Model B.
^aHeat wave indicator denotes any day that is part of 2 or more consecutive days when maximum temperature was above the 95^th percentile for the MSA.
^bHoliday indicator denotes a U.S. Federal holiday. ^cHeat wave indicator denotes any day that is part of 2 or more consecutive days when SSC indicator of extreme heat.

ISSN: 1476-069X