Short-Term Nitrogen Dioxide Exposure and Emergency Hospital Admissions for Asthma in Children: A Case-Crossover Analysis in England

Figures & data

Table 1 Characteristics of Asthma Emergency Hospital Admissions of Children Aged 0–14 in England between 2011 and 2015

	Asthma-Related Hospital Admission (Age 0–14 Years)		%Total Population Aged 0–14 of England^a
	n = 111,766	%
Age Group (Years)
0–4	47,771	42.8	35.4
5–9	41,161	36.8	31.7
10–14	22,834	20.4	32.9
Sex
Male	70,106	62.7	51.2
Female	41,660	37.3	48.8
Season^b
Warm	52,835	47.3	–
Cold	58,931	52.7	–
Income Deprivation Quintile^c
1 (least deprived)	12,489	11.2	18.9
2	15,290	13.7	18.1
3	18,776	16.8	18.6
4	25,923	23.2	20.4
5 (most deprived)	39,288	35.1	24.0
Region of England
South West	8275	7.4	10.0
Yorkshire and the Humber	10,592	9.5	9.8
East Midlands	6143	5.5	8.6
London	18,185	16.3	15.9
North West	22,905	20.5	13.1
West Midlands	16,393	14.7	10.5
East of England	9638	8.6	11.1
South East	13,873	12.4	16.3
North East	5762	5.1	4.7
Patient-to-hospital Distance
≤10 kilometres	81,635	73.0	–
>10 kilometres	30,131	27.0	–

Notes: ^aBased on 2011 census, data source: Office for National Statistics (www.ons.gov.uk). ^bCold season: October to March; Warm season: April to September. ^cBased on Index of Multiple Deprivation 2015, Income Domain.

Figure 1 Flow chart of case selection.

Figure 2 Daily average count of asthma-related emergency hospital admissions in children in England by month, averaged across 2011–2015.

Figure 3 Odds ratios and 95% confidence intervals for asthma-related emergency hospital admissions in children associated per 10 μg/m³ increase in NO₂ (lag 0–4), including overall effect size and stratification by age, sex, season, income deprivation quintile, and region. P-value for difference was calculated using a Wald test to compare the difference between subgroups.