Background: Evidence suggests that oxidative stress is a unifying feature underlying the toxic actions of particulate matter (PM). We have investigated whether individual plasma antioxidant concentrations (uric acid and vitamins C, A, and E) and 10 antioxidant genes modify the response to PM with respect to hospital admissions for chronic obstructive pulmonary disease (COPD) or asthma.
Methods: Using a bidirectional, hospital-based, case-crossover study, 209 patients admitted for asthma or COPD to the Chelsea and Westminster Hospital (London), with 234 admissions, were recruited between May 2008 and July 2010. PM10 levels in the area of Kensington and Chelsea at the time of admission were compared with the levels 14 days before and 14 days after the event. Conditional logistic regression was used to estimate the effect of PM10 at several temporal lags, while controlling for confounders.
Results: An increase in asthma/COPD admission rate was related to a 10 μg/m3 increase in PM10, with the highest effect noted 0–3 days before the exacerbation (for lag 0–3, odds ratio = 1.35 [95% confidence interval = 1.04–1.76]). Serum vitamin C modified the effect of PM10 on asthma/COPD exacerbations. A similar (although weaker) influence was observed for low levels of uric acid and vitamin E, whereas vitamin A showed no effect modification. GSTP1 (rs1695), SOD2 (rs4880), and Nrf2 (rs1806649) were associated with a trend toward an increased risk of hospital admissions during periods of high PM10 levels.
Conclusions: Our study suggests that the concentration of antioxidants in patients' serum modifies the short-term effects of PM10 on asthma and COPD exacerbations.
From the aMRC-HPA Centre for Environment and Health, Imperial College, London, United Kingdom; bMRC-HPA Centre for Environment and Health, King's College, London, United Kingdom; cInstitute of Genetic Medicine, EURAC, Bolzan, Italy; dNHLI, Imperial College, London; and eChelsea and Westminster Hospital, London, United Kingdom.
Submitted 20 June 2011; accepted 7 February 2012; posted 23 April 2012.
Supported by grants from the UK Department of Health's Policy Research Programme, and the Medical Research Council and the Health Protection Agency through the MRC-HPA Centre for Environment and Health. The authors reported no other financial interests related to this research.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.
Correspondence: Cristina Canova, MRC-HPA Centre for Environment and Health, Respiratory Epidemiology and Public Health Group, National Heart and Lung Institute, Emmanuel Kaye Building, Manresa Road, Imperial College, London SW3 6LR, United Kingdom. E-mail: firstname.lastname@example.org.