Trends in serum cotinine concentrations among daily cigarette smokers: Data from NHANES 1999-2010

- Serum cotinine levels increased over time for males, females, and whites.
- CFM nicotine levels increased over time for males, females, whites and blacks.
- Cigarettes smoked per day decreased over time for females, whites, and blacks.
- CFM tar levels decreased over time for Mexican Americans.
- Serum cotinine levels increased with exposure to second hand smoke at home.

To the best of our knowledge, there have been no apparent studies of the trends in serum cotinine levels among smokers. Data from National Health and Nutrition Examination Survey for the period 1999-2010 were used to evaluate trends for serum cotinine levels; average number of cigarettes smoked per day; and Cambridge filter method (CFM) tar and CFM nicotine levels by gender, race/ethnicity, and cigarette mentholation status. Regression models were fitted to evaluate the factors associated with serum cotinine levels. Serum cotinine levels increased over time for both males and females, non-Hispanic whites and others. CFM nicotine levels also rose over time for cigarettes smoked by both males and females and by both non-Hispanic whites and non-Hispanic blacks. Average number of cigarettes smoked per day decreased over time for females, non-Hispanic whites and non-Hispanic blacks. CFM tar levels fell only for Mexican Americans. Exposure to second hand smoke at home was found to be associated with more than 1 ng/ml increase in serum cotinine levels. This large study on a nationally representative sample of daily smokers suggested that increasing concentrations of CFM nicotine in cigarettes over time led to elevated serum cotinine levels even though the number of cigarettes smoked daily remained relatively constant.