Longer term exposure to secondhand smoke and health outcomes in COPD: impact of urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol

Abstract

Introduction: Secondhand smoke (SHS) contains respiratory irritants and has the potential to adversely affect adults with chronic obstructive pulmonary disease (COPD), but few studies have evaluated the impact of SHS on COPD.

Methods: We used data from 72 nonsmoking participants in a cohort study of COPD. Urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was measured as an indicator of longer term SHS exposure, whereas urine cotinine was assessed as a measure of more recent exposure. The impact of SHS exposure on COPD-related health status was examined using multivariate linear regression (controlling for age, sex, race, educational attainment, and smoking history). Health status was measured using a validated COPD severity score, reported dyspnea, a standard health status measure (Short Form-12), and activity restriction.

Results: The urine NNAL-to-creatinine ratio (per interquartile increment) was associated with greater COPD severity (mean score increase 1.7 points; 95% CI 0.6-2.8; p = .0003). Higher urine NNAL was also related to greater dyspnea, poorer physical health status, and more restricted activity (p < or = .05 in all cases). When considered simultaneously, longer term exposure (NNAL) had a greater negative impact on COPD status than shorter term exposure (cotinine).

Discussion: Urine NNAL can be used to estimate longer term SHS exposure and negatively affects a number of health outcomes among adults with COPD. Screening for and prevention of SHS exposure among persons with COPD may be beneficial.

Figure 1.

Details of sampling and recruitment for baseline through Wave 3. Wave 2 attempted to recruit all subjects who indicated a diagnosis of asthma or chronic obstructive pulmonary disease (COPD) at baseline. Wave 3 attempted to recruit all subjects followed in Wave 2 plus those who indicated a diagnosis of allergic rhinitis or obstructive sleep apnea at baseline. The participants in the current study included subjects with COPD who completed Wave 3 follow-up, were current nonsmokers, and had urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol measured.

Figure 2.

Longer term secondhand smoke exposure and chronic obstructive pulmonary disease (COPD) severity. (a) Locally weighted regression scatter plot smoother (LOWESS) procedure was used to graphically depict the relationship between 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL)-to-creatinine ratio and COPD severity score in a flexible manner (shown in orange). The blue line is the fitted linear regression line. The gray area shows the 95% CI. (b) LOWESS plot of COPD severity score residuals that adjust for age, sex, race, educational attainment, and smoking history, and NNAL-to-creatinine ratio (orange line). The blue line is the fitted linear regression line. The gray area shows the 95% CI.