Indoor Pollutant Exposure Is Associated With Heightened Respiratory Symptoms in Atopic Compared to Non-atopic Individuals With COPD

Deepak A Kaji; Andrew J Belli; Meredith C McCormack; Elizabeth C Matsui; D'Ann L Williams; Laura Paulin; Nirupama Putcha; Roger D Peng; Gregory B Diette; Patrick N Breysse; Nadia N Hansel

Disclosures

BMC Pulm Med. 2014;14(147)

Abstract and Introduction

Abstract

Background Indoor particulate matter (PM) has been linked to respiratory symptoms in former smokers with COPD. While subjects with COPD and atopy have also been shown to have more frequent respiratory symptoms, whether they exhibit increased susceptibility to PM as compared to their non-atopic counterparts remains unclear. The aim of this study was to determine whether atopic individuals with COPD have greater susceptibility to PM compared to non-atopic individuals with COPD.

Methods Former smokers with moderate to severe COPD were enrolled (n = 77). PM_2.5, PM with diameter <2.5 micrometers, was measured in the main living area over three one-week monitoring periods at baseline, 3, and 6 months. Quality of life, respiratory symptoms and medication use were assessed by questionnaires. Serum was analyzed for specific IgE for mouse, cockroach, cat, dog and dust mite allergens. Atopy was established if at least one test was positive. Interaction terms between PM and atopy were tested and generalized estimating equation analysis determined the effect of PM concentrations on health outcomes. Multivariate models were adjusted for age, sex, education, race, season, and baseline lung function and stratified by atopic status.

Results Among atopic individuals, each 10 μg/m³ increase in PM was associated with higher risk of nocturnal symptoms (OR, 1.95; P = 0.02), frequent wheezing (OR, 2.49; P = 0.02), increased rescue medication use (β = 0.14; P = 0.02), dyspnea (β = 0.23; P < 0.001), higher St. George's Respiratory Quality of Life score (β = 2.55; P = 0.01), and higher breathlessness, cough, and sputum score (BCSS) (β = 0.44; P = 0.01). There was no association between PM and health outcomes among the non-atopic individuals. Interaction terms between PM_2.5 and atopy were statistically significant for nocturnal symptoms, frequency of rescue medication use, and BCSS (all P < 0.1).

Conclusions Individuals with COPD and atopy appear to be at higher risk of adverse respiratory health effects of PM exposure compared to non-atopic individuals with COPD.

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Abstract and Introduction
Background
Methods
Results
Discussion
Conclusion
References

Table 1. Baseline participant characteristics
Participant characteristics	Non atopic (n = 54)	Atopic (n = 23)	p
Age, mean (SD)	69.3 (7.1)	69.7 (7.1)	0.86
Gender, % male	63	57	0.60
Race, (%)
Caucasian	89	83	0.71
Black/African American	9	13
Other	2	4
Education, (%)
< High School	19	22	0.63
High School	24	9
Some College	30	39
Bachelor's Degree	13	13
At least some Graduate School	15	17
Smoking History, mean (SD)
Pack Years	56.8 (28.4)	60.7 (31.0)	0.60
Last Cigarette (Years Since)	13.0 (9.7)	13.4 (8.0)	0.85
Baseline Health Status
Post Bronchodilator FEV₁% predicted, mean (SD)	52.4 (16.11)	51.9 (17.29)	0.89
Pre FEV₁/FVC	0.50 (0.10)	0.52 (0.10)	0.45
Post FEV₁/FVC	0.51 (0.10)	0.54 (0.11)	0.28
Bronchodilator reversibility, (%)	31.5	30.4	0.93
Chronic Bronchitis (%)	39	35	0.73
Emphysema (%)	57	70	0.32
SGRQ, mean (SD)	38.6 (17.6)	42.0 (20.7)	0.47
MMRC, mean (SD)	2.6 (1.0)	2.5 (1.2)	0.63
Medication list, (%)
Long acting beta agonist (LABA)	8	4	0.61
Inhaled Corticosteroids (ICS)	19	5	0.12
ICS/LABA combination	44	65	0.10
Long acting muscarinic antagonist	37	43	0.60
Nasal steroids	6	9	0.61
Leukotriene modifiers	8	9	0.88
Theophylline	2	9	0.16
Antihistamine	2	9	0.16
Comorbidities, (%)
Congestive heart failure	6	9	0.61
Diabetes	19	26	0.45
Cancer	19	22	0.74
Myocardial infarction	11	22	0.22
Hypertension	59	61	0.90
Kidney disease	2	0	0.51

Please note some of the data from the above table were previously published in a manuscript from the CODE cohort [5].
BCSS = Breathlessness, Cough, and Sputum Scale.
SGRQ = St. George's Respiratory Questionnaire.
MMRC = Modified Medical Research Council.
FEV₁ = Forced expiratory volume in 1 second.
FVC = Forced vital capacity.
SD = Standard deviation.

Table 2. Bivariate association of indoor pollutant concentrations* and respiratory health
Bivariate analysis	Non-atopic participants (n = 54)			Atopic participants (n = 23)
Bivariate analysis	β	p	95% CI	β	p	95% CI
MMRC (dyspnea)	0.11	0.31	[−0.11,0.33]	0.21	0.01	[0.06,0.37]
Rescue medication use	0.06	0.49	[−0.11,0.24]	0.18	0.03	[0.02,0.34]
BCSS	−0.28	0.13	[−0.65,0.09]	0.32	0.09	[−0.05,0.69]
SGRQ	1.04	0.47	[−1.77,3.85]	2.15	0.05	[0.03,4.27]
	OR	p	95% CI	OR	p	95% CI
Wheeze	1.38	0.14	[0.90,2.11]	2.25	0.01	[1.22,4.14]
Nocturnal symptoms	1.00	0.98	[0.55,1.80]	1.76	0.04	[1.02,3.01]
Cough	0.76	0.27	[0.46,1.24]	1.11	0.50	[0.82,1.51]
Phlegm	1.09	0.67	[0.72,1.66]	1.15	0.37	[0.84,1.57]
Severe exacerbations	0.89	0.81	(0.35, 2.28)	1.27	0.21	(0.87, 1.83)

BCSS = Breathlessness, Cough, and Sputum Scale.
SGRQ = St. George's Respiratory Questionnaire.
MMRC = Modified Medical Research Council.
*ORs and coefficients represent difference in stated outcomes for every 10 point change in PM_2.5.
Bold values represent statistically significant associations (p < 0.05).

Table 3. Multivariate analyses of association of indoor pollutant concentrations and respiratory health*
Multivariate analysis	Non-atopic participants (n = 54)			Atopic participants (n = 23)			int(p)
Multivariate analysis	β	p	95% CI	β	p	95% CI	int(p)
MMRC	0.08	0.52	[−0.16, 0.32]	0.23	<0.001	[0.09, 0.34]	0.62
Rescue medication use	0.01	0.90	[−0.18, 0.20]	0.14	0.02	[0.02, 0.26]	<0.001
BCSS	−0.30	0.13	[−0.70, 0.09]	0.44	0.01	[0.11, 0.76]	0.08
SGRQ	1.06	0.45	[−1.67, 3.80]	2.55	0.01	[0.69, 4.41]	0.44
	OR	p	95% CI	OR	p	95% CI
Frequent wheeze	1.16	0.56	[0.71, 1.88]	2.49	0.02	[1.17, 5.30]	0.17
Nocturnal symptoms	0.60	0.19	[0.29, 1.27]	1.95	0.02	[1.09, 3.48]	0.03
Cough	0.70	0.20	[0.41, 1.20]	1.26	0.23	[0.86, 1.85]	0.28
Phlegm	1.25	0.37	[0.77, 2.05]	1.32	0.15	[0.91, 1.93]	0.79
Severe exacerbations	0.87	0.79	[0.31, 2.42]	2.12	0.03	[1.06, 4.27]	0.63