Biomarker Helps to Confirm Mortality Risk with Second-Hand Smoke

Serum cotinine, a metabolite of nicotine, is a better indicator of secondhand smoke exposure and subsequent health risk than self-reported questionnaires, according to new research.

Nonsmokers are exposed to secondhand smoke without realizing it. Therefore, they may not be aware of their risk of lung cancer or other smoking-related disease. For this reason, researchers aimed to determine whether measuring cotinine levels in the blood would be a better indicator of subsequent health risk.
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To conduct their study, the researchers analyzed data from 20,175 participants aged 20 years and older in the National Health and Nutrition Examination Survey (NHANES) who self-reported not smoking (with and without secondhand smoke exposure). Data were collected from 1999 to 2010 and were compared with National Death Index data.

At baseline, the researchers measured serum cotinine levels and categorized nonsmokers based on reported race-specific cutoff points: 5.92 ng/mL for non-Hispanic blacks, 4.85 ng/mL for non-Hispanic whites, 0.84 ng/mL for Mexican Americans, and 3.08 ng/mL for all other groups.

After adjusting for multiple variables, the researchers found that serum cotinine levels indicated a significant increase in years of life lost across all concentrations (range: 5.6 years of life lost in the lowest quartile to 7.5 years of life lost in the highest quartile).

Cotinine levels were also significantly associated with overall survival, all-cause mortality, lung cancer, all cancers, and heart diseases in participants who did and did not report secondhand smoke exposure.

“Serum cotinine levels identify [secondhand smoke]-attributable mortality in subjects who would have otherwise been overlooked by questionnaire data, providing further evidence that the economic toll of [secondhand smoke] may be substantially higher than what was reported based on questionnaires,” the researchers concluded.

—Amanda Balbi

Reference:

Flores RM, Liu B, Taioli E. Association of serum cotinine levels and lung cancer mortality in non-smokers [published online September 7, 2016]. Carcinogenesis. doi:10.1093/carcin/bgw094.