Effect modification by race-ethnicity of environmental tobacco smoke exposure on airway inflammation in US children

Tobacco smoke exposure and fractional exhaled nitric oxide levels among U.S. adolescents

BACKGROUND

Fractional exhaled nitric oxide (FeNO) can objectively guide clinical practice in the assessment, diagnosis, and treatment of eosinophilic airway inflammation. FeNO values may be affected by current smoking, but the role of tobacco smoke exposure (TSE) is understudied.

OBJECTIVE

This study investigated the associations between biochemically validated and self-reported TSE and FeNO levels among U.S. nonsmoking adolescents without asthma.

METHODS

National Health and Nutrition Examination Survey 2007-2012 data were used. TSE was assessed via serum cotinine and self-reported measures. We assessed FeNO continuously and using cutpoints of >35 ppb and >50 ppb to indicate likely eosinophilic inflammation in children and adults, respectively. We conducted linear and logistic regression adjusting for potential covariates.

RESULTS

Overall, 34.0% of adolescents had low cotinine (0.05-2.99 ng/ml), 6.2% had high cotinine (≥3.00 ng/ml), and 11.9% had home TSE. Compared to adolescents with no/minimal cotinine, adolescents with high cotinine were at reduced odds to have FeNO >35 ppb (adjusted odds ratio [aOR] = 0.54, 95%CI = 0.43,0.69). Adolescents with low cotinine had lower FeNO values (β = -2.05, 95%CI = -3.61,-0.49), and were also at decreased odds to have FeNO >35 ppb (aOR = 0.74, 95%CI = 0.66,0.83) and FeNO >50 ppb (aOR = 0.62, 95%CI = 0.53,0.72). Adolescents with home TSE were at reduced odds to have FeNO >50 ppb (aOR = 0.72, 95%CI = 0.57,0.91) than adolescents without home TSE. Adolescents with a higher number of cigarettes/day smoked inside their home were at reduced odds to have FeNO >35 ppb (OR = 0.98, 95%CI = 0.97,0.99) and FeNO >50 ppb (OR = 0.98, 95%CI = 0.96,0.99).

CONCLUSIONS

TSE was associated with decreased FeNO levels. The addition of TSE may be clinically important when interpreting thresholds for FeNO.

Smokeless tobacco use and fractional exhaled nitric oxide in men in a national survey

BACKGROUND

Tobacco use is an important risk for asthma and increases asthma severity. Fractional exhaled nitric oxide (FeNO) is used as a noninvasive biomarker of eosinophilic airway inflammation. Substantial numbers of men use smokeless tobacco. The effect of use of smokeless tobacco on FeNO is not known.

OBJECTIVE

To estimate the association between use of smokeless tobacco and FeNO among US men.

METHODS

The National Health and Nutrition Examination Survey 2007-2012 was analyzed to assess association of use of smokeless tobacco and FeNO levels in parts per billion in US men. Participants were categorized by smoking status and use of snuff or chewing tobacco in the previous 5 days. FeNO was measured using a device that relies on an electrochemical sensor.

RESULTS

In 3,791 male nonsmokers without asthma, weighted mean natural logarithm FeNO by exposure to smokeless tobacco was 2.81 (geometric mean FeNO, 16.59 ppb; 95% CI, 2.77-2.85) in unexposed and 2.66 (geometric mean, 14.30 ppb; 95% CI, 2.55-2.77) in the exposed. In weighted linear regression analyses, use of smokeless tobacco was associated with significantly lower natural logarithm FeNO after controlling for age and race (black vs nonblack) (coefficient, -0.124; SE, 0.056; P = .03; 95% CI, -0.237 to -0.011). Results were unchanged after additionally controlling for recent nitric oxide-rich vegetable consumption and upper respiratory tract infection (coefficient, -0.118; SE, 0.055; P = .04; 95% CI, -0.228 to -0.007).

CONCLUSIONS

Use of smokeless tobacco was associated with lower mean natural logarithm FeNO levels in nonsmokers with no history of asthma. Interpretation of FeNO should consider all forms of tobacco use.