Secondhand smoke exposure and asthma outcomes among African-American and Latino children with asthma

Abstract

Background Secondhand smoke (SHS) exposures have been linked to asthma-related outcomes but quantitative dose-responses using biomarkers of exposure have not been widely reported.Objectives A ssess dose-response relationships between plasma cotinine-determined SHS exposure and asthma outcomes in minority children, a vulnerable population exposed to higher levels of SHS and underrepresented in the literature.Methods We performed analyses in 1172 Latino and African-American children with asthma from the mainland USA and Puerto Rico.We used logistic regression to assess relationships of cotinine levels =0.05 ng/mL with asthma exacerbations (defined as asthma-related hospitalisations, emergency room visits or oral steroid prescription) in the previous year and asthma control.The shape of dose-response relationships was assessed using a continuous exposure variable in generalised additive logistic models with penalised splines.Results T he OR for experiencing asthma exacerbations in the previous year for cotinine levels =0.05 ng/mL, compared with <0.05 ng/mL, was 1.40 (95% CI 1.03 to 1.89), while the OR for poor asthma control was 1.53 (95% CI 1.12 to 2.13).Analyses for dose-response relationships indicated increasing odds of asthma outcomes related with increasing exposure, even at cotinine levels associated with light SHS exposures.Conclusions E xposure to SHS was associated with higher odds of asthma exacerbations and having poorly controlled asthma with an increasing dose-response even at low levels of exposure.Our results support the conclusion that there are no safe levels of SHS exposures.