Pediatric asthma hospitalization: individual and environmental characteristics of high utilizers in South Texas

Figures & data

Table A1. List of 15 factors for social vulnerability index

	Factor	Description
Socioeconomic status	Below poverty	Percent of persons below federally defined poverty line
	Unemployed	Percent of persons aged 16+ unemployed
	Income	Per capita income
	No high school diploma	Percent of persons aged 25 years and old, with less than a 12th grade education
Household composition and disability	Aged 65 or older	Percent of persons aged 65 years or older
	Aged 17 or younger	Percent of persons aged 17 years or younger
	Civilian with a disability	Percent of persons more than 5 years old with a disability
	Single-parent households	Percent of male or female householder, no spouse present, with children under 18
Minority status and language	Minority	Percent of minority
	Speak English “less than well”	Percent of persons aged 5 years or older who speak English less than “well”
Housing and transportation	Multi-unit structures	Percent of housing units with 10 or more units in structure
	Mobile homes	Percent of housing units that are mobile homes
	Crowding	Percent of total occupied housing units with more than one person per room
	No vehicle	Percent of households with no vehicle available
	Group quarters	Percent of persons who are in institutionalized group quarters (e.g. nursing homes) and non-institutionalized group quarters (e.g. college dormitories, military quarters)

Figure 1. Hospital resource utilization of pediatric patients with asthma admitted to Driscoll Children’s hospital during 2010–2016.

Table 1. Comparison of hospital resource utilization among low, medium, and high groups in pediatric asthma hospitalizations.

	Median (IQR) or N (%)				p Value
		Number of pediatric asthma hospitalization
	Total	Low group (1 time)	Medium group (2 or 3 times)	High group (≥4 times)
Number of patients	902 (100.0%)	759 (84.2%)	121 (13.4%)	22 (2.4%)
Average number of hospitalizations	1 (1–1)	1 (1–1)	2 (2–2)	5 (4–6)	<0.001
Average number of days spent in the hospital across hospitalizations	2 (1–3)	1 (1–2)	4 (3–5)	12 (10–14)	<0.001
Time between hospitalizations (days)	274 (106–539)	NA	331 (178–664)	169 (56–355)	<0.001
Time between hospitalizations	252 (100.0%)		149 (100.0%)	103 (100.0%)
1–30 days	20 (7.9%)	NA	10 (6.7%)	10 (9.7%)	<0.001
31–90 days	36 (14.3%)		11 (7.4%)	25 (24.3%)
91–365 days	103 (40.9%)		60 (40.3%)	43 (41.7%)
366 days or longer	93 (36.9%)		68 (45.6%)	25 (24.3%)

Note: IQR, Interquartile range; NA, not applicable; p values from Kruskal–Wallis tests for continuous variables and Chi-square tests for categorical variable.

Table A2. Pearson correlation coefficients between ambient air pollutants and social vulnerability index.

	PM2.5	Ozone	SVI
PM2.5	1
Ozone	−0.4327*	1
SVI	0.2109*	−0.2975*	1

Note: * p < 0.001.

Table 2. Comparison of patient and environmental characteristics among hospital utilization groups.

Variables	Median (IQR) or N (%)				p Value
	Total (N = 902)	Low group (N = 759)	Medium group (N = 121)	High group (N = 22)
Individual-level characteristics (at index admission)
Age (years)	8 (6-11)	8 (6-12)	8 (6-10)	7 (6-10)	0.194
Age					0.090
5–11 years	686 (76.1)	567 (74.7)	101 (83.5)	18 (81.8)
12–18 years	216 (23.9)	192 (25.3)	20 (16.5)	4 (18.2)
Gender					0.479
Male	536 (59.4)	445 (58.6)	78 (64.5)	13 (59.1)
Female	366 (40.6)	314 (41.4)	43 (35.5)	9 (40.9)
Ethnicity					0.775
Hispanic	677 (75.2)	567 (74.9)	94 (77.7)	16 (72.7)
Non-Hispanic	223 (24.8)	190 (25.1)	27 (22.3)	6 (27.3)
Type of insurance					0.794
Public (Medicaid)	617 (68.4)	516 (68.0)	86 (71.1)	15 (68.2)
Private or self-pay	285 (31.4)	243 (32.0)	35 (28.9)	7 (31.8)
Use of medication					0.965
Yes	832 (92.2)	700 (92.2)	112 (92.6)	20 (90.9)
No	70 (7.8)	59 (7.8)	9 (7.4)	2 (9.1)
Length of stay (days)	2 (1–2)	1 (1–2)	2 (1–3)	2 (2–3)	<0.001
Length of stay					<0.001
1 day	430 (47.6)	387 (51.0)	38 (31.4)	5 (22.7)
2 days	291 (32.3)	241 (31.7)	41 (33.9)	9 (40.9)
3 days or longer	181 (20.1)	131 (17.3)	42 (34.7)	8 (36.4)
Season					0.376
Warm	355 (39.4)	292 (38.5)	52 (43.0)	11 (50.0)
Cold	547 (60.6)	467 (61.5)	69 (57.0)	11 (50.0)
Year					<0.001
2010	171 (19.0)	132 (17.4)	27 (22.3)	12 (54.5)
2011	138 (15.3)	105 (13.8)	27 (22.3)	6 (27.3)
2012	162 (18.0)	138 (18.2)	22 (18.2)	2 (9.1)
2013	130 (14.4)	106 (14.0)	22 (18.2)	2 (9.1)
2014	136 (15.1)	121 (15.9)	15 (12.4)	0 (0.0)
2015	75 (8.3)	67 (8.8)	8 (6.6)	0 (0.0)
2016	90 (9.9)	90 (11.9)	0 (0.0)	0 (0.0)
Environmental characteristics
SVI (continuous)	0.68 (0.49-0.83)	0.68 (0.49-0.84)	0.68 (0.48-0.81)	0.67 (0.57-0.81)	0.809
SVI (categorical)					0.138
Quartile 1 (the lowest)	235 (24.9)	186 (24.5)	35 (28.9)	4 (18.2)
Quartile 2	236 (26.2)	201 (26.5)	25 (20.7)	10 (45.5)
Quartile 3	216 (24.0)	177 (23.3)	36 (29.7)	3 (13.6)
Quartile 4 (the highest)	225 (24.9)	195 (25.7)	25 (20.7)	5 (22.7)
PM2.5 (continuous)	8.52 (8.32–8.63)	8.51 (8.31–8.63)	8.53 (8.37–8.64)	8.51 (8.38–8.66)	0.454
PM2.5 (categorical)					0.335
Quartile 1 (the lowest)	229 (25.4)	202 (26.6)	24 (19.8)	3 (13.6)
Quartile 2	222 (24.6)	183 (24.1)	30 (24.8)	9 (40.9)
Quartile 3	228 (25.3)	190 (25.0)	34 (28.1)	4 (18.2)
Quartile 4 (the highest)	223 (24.7)	184 (24.2)	33 (27.3)	6 (27.3)
Ozone (continuous)	36.01 (35.8–36.29)	36.02 (35.8–36.3)	35.97 (35.87–36.19)	36.20 (35.97–36.33)	0.160
Ozone (categorical)					0.052
Quartile 1 (the lowest)	211 (23.4)	183 (24.1)	25 (20.7)	3 (13.6)
Quartile 2	240 (26.6)	193 (25.4)	44 (36.4)	3 (13.6)
Quartile 3	217 (24.1)	180 (23.7)	28 (23.1)	9 (40.9)
Quartile 4 (the highest)	234 (25.9)	203 (26.8)	24 (19.8)	7 (31.8)

Note: IQR, Interquartile range; p values from Kruskal–Wallis tests for continuous variables and Chi-square tests for categorical variables.

Table 3. Results of bivariate and multivariate ordered logistic regression analysis among hospital utilization groups.

	Unadjusted model		Adjusted models
	OR (95% CI)	p Value	OR (95% CI)	p Value	OR (95% CI)	p Value
Individual-level characteristics (at index admission)
Age
5–11 years	Ref.	0.031	Ref.	0.020	Ref.	0.025
12–18 years	0.60 (0.37, 0.95)		0.56 (0.35, 0.91)		0.57 (0.35, 0.93)
Gender
Male	Ref.	0.277	Ref.	0.204	Ref.	0.229
Female	0.81 (0.56, 1.18)		0.78 (0.53, 1.14)		0.79 (0.53, 1.16)
Ethnicity
Non-Hispanic	Ref.	0.630	Ref.	0.455	Ref.	0.538
Hispanic	1.11 (0.73, 1.69)		1.18 (0.76, 1.84)		1.16 (0.73, 1.83)
Type of insurance
Private or self-pay	Ref.	0.544	Ref.	0.662	Ref.	0.627
Public (Medicaid)	1.13 (0.76, 1.67)		1.09 (0.73, 1.64)		1.11 (0.72, 1.72)
Use of medication
No	Ref.	0.987	Ref.	0.626	Ref.	0.627
Yes	1.01 (0.51, 1.96)		1.19 (0.59, 2.40)		1.22 (0.60, 2.49)
Length of stay
1 day	Ref.		Ref.		Ref.
2 days	1.88 (1.22, 2.92)	0.005	1.80 (1.15, 2.81)	0.011	1.80 (1.15, 2.84)	0.011
3 days or longer	3.43 (2.18, 5.39)	<0.001	3.23 (2.01, 5.17)	<0.001	3.38 (2.10, 5.46)	<0.001
Season
Cold	Ref.	0.197	Ref.	0.034	Ref.	0.042
Warm	1.27 (0.88, 1.82)		1.51 (1.03, 2.20)		1.49 (1.01, 2.20)
Admission year	0.75 (0.67, 0.83)	<0.001	0.76 (0.68, 0.85)	<0.001	0.76 (0.68, 0.86)	<0.001
Environmental characteristics
Social vulnerability index
Quartile 1 (the lowest)	Ref.				Ref.
Quartile 2	0.86 (0.52, 1.41)	0.551			0.84 (0.48, 1.45)	0.525
Quartile 3	1.04 (0.64, 1.70)	0.862			0.89 (0.50, 1.56)	0.674
Quartile 4 (the highest)	0.74 (0.44, 1.25)	0.261			0.63 (0.34, 1.16)	0.135
PM2.5 level
Quartile 1 (the lowest)	Ref.				Ref.
Quartile 2	1.63 (0.96, 2.76)	0.071			1.42 (0.75, 2.71)	0.280
Quartile 3	1.49 (0.88, 2.53)	0.141			1.27 (0.62, 2.59)	0.514
Quartile 4 (the highest)	1.59 (0.94, 2.70)	0.085			1.48 (0.71, 3.09)	0.298
Ozone level
Quartile 1 (the lowest)	Ref.				Ref.
Quartile 2	1.57 (0.94, 2.60)	0.084			1.78 (1.01, 3.14)	0.045
Quartile 3	1.38 (0.81, 2.34)	0.238			1.43 (0.77, 2.67)	0.260
Quartile 4 (the highest)	1.02 (0.59, 1.76)	0.954			1.30 (0.64, 2.65)	0.469

Table A3. Results of multivariate ordered logistic regression analysis for each pollutant.

	PM2.5 model		Ozone model
	OR (95% CI)	p Value	OR (95% CI)	p Value
Age
5–11 years	Ref.		Ref.
12–18 years	0.56 (0.35, 0.92)	0.021	0.56 (0.34, 0.91)	0.020
Gender
Male	Ref.		Ref.
Female	0.79 (0.54, 1.17)	0.251	0.79 (0.53, 1.16)	0.226
Ethnicity
Non-Hispanic	Ref.		Ref.
Hispanic	1.17 (0.74, 1.84)	0.503	1.16 (0.73, 1.83)	0.522
Type of insurance
Private or self-pay	Ref.		Ref.
Public (Medicaid)	1.13 (0.73, 1.73)	0.585	1.11 (0.73, 1.73)	0.595
Use of medication
No	Ref.		Ref.
Yes	1.16 (0.57, 2.36)	0.680	1.24 (0.61, 2.53)	0.553
Length of stay
1 day	Ref.		Ref.
2 days	1.81 (1.15, 2.84)	0.010	1.77 (1.13, 2.78)	0.013
3 days or longer	3.37 (2.10, 5.43)	<0.001	3.33 (2.07, 5.36)	<0.001
Season
Cold	Ref.		Ref.
Warm	1.47 (1.00, 2.15)	0.050	1.51 (1.03, 2.22)	0.036
Admission year	0.77 (0.69, 0.86)	<0.001	0.76 (0.68, 0.85)	<0.001
Social vulnerability index
Quartile 1 (lowest)	Ref.		Ref.
Quartile 2	0.87 (0.51, 1.49)	0.617	0.79 (0.47, 1.35)	0.395
Quartile 3	0.93 (0.54, 1.61)	0.807	0.85 (0.48, 1.48)	0.559
Quartile 4 (highest)	0.65 (0.36, 1.18)	0.161	0.61 (0.33, 1.11)	0.106
PM2.5 level
Quartile 1 (lowest)	Ref.
Quartile 2	1.42 (0.75, 2.71)	0.280
Quartile 3	1.27 (0.62, 2.59)	0.514
Quartile 4 (highest)	1.48 (0.71, 3.09)	0.298
Ozone level
Quartile 1 (lowest)			Ref.
Quartile 2			1.79 (1.05, 3.06)	0.036
Quartile 3			1.40 (0.80, 2.45)	0.242
Quartile 4 (highest)			1.06 (0.58, 1.93)	0.842