Pediatric patient asthma-related emergency department visits and admissions in Washington, DC, from 2001–2004, and associations with air quality, socio-economic status and age group

Table 3 Lagged Day Associations of ED Visits with Ozone and Pollen.

Visits 1–17 yrs
	Ozone		Tree Pollen		Grass Pollen
Lag (days)	Mean % Change in Daily Visits per Unit	T-test p-value	Mean % Change in Daily Visits per Unit	T-test p-value	Mean % Change in Daily Visits per Unit	T-test p-value
0	1 (-0.1, 2.1)	0.078	0.5 (0, 1.1)	0.068	0.7 (-1.8, 3.1)	0.602
1	0.1 (-1, 1.2)	0.879	0.4 (-0.2, 1)	0.202	1.9 (-0.4, 4.3)	0.112
2	-0.2 (-1.3, 0.9)	0.724	0.5 (-0.1, 1.1)	0.105	2.3 (-0.1, 4.7)	0.056
3	0.3 (-0.8, 1.5)	0.572	0.2 (-0.4, 0.8)	0.492	2.6 (0.3, 5)	0.030
4	0.2 (-0.9, 1.3)	0.754	0.2 (-0.4, 0.9)	0.441	-0.4 (-2.9, 2.3)	0.787
Visits 5–12 yrs
	Ozone		Tree Pollen		Grass Pollen
Lag (days)	Mean % Change in Daily Visits per Unit	T-test p-value	Mean % Change in Daily Visits per Unit	T-test p-value	Mean % Change in Daily Visits per Unit	T-test p-value
0	3.2 (1.4, 5)	0.000	1.8 (0.9, 2.6)	0.0001	1.6 (-2, 5.4)	0.378
1	1.9 (0.2, 3.7)	0.030	1.2 (0.4, 2.1)	0.005	3.5 (0.1, 7.1)	0.046
2	2.3 (0.6, 4.1)	0.009	1.5 (0.7, 2.4)	0.0002	4.3 (0.9, 7.9)	0.013
3	2.8 (1.1, 4.6)	0.002	1.1 (0.3, 2)	0.01	5.5 (2.2, 9)	0.001
4	3.3 (1.6, 5.1)	0.000	1.1 (0.2, 2)	0.016	3.1 (-0.5, 6.8)	0.088

The top and bottom tables are for the 1–17 yr old and 5–12 yr old age groups, respectively. The mean % change in daily visits in these tables is per unit 0.01 ppm increase in ozone, 100 grains m^-3 increase in tree pollen, and 10 grains m^-3 increase in grass pollen.

ISSN: 1476-069X