Concentrations of serum cotinine across stages of glomerular function among US adult smokers and nonsmokers.

Data from National Health and Nutrition Examination Survey for 1999-2016 were used to investigate variabilities in serum cotinine levels for US adult smokers (N = 8951) and nonsmokers (N = 28,205) aged ≥ 20 years across the stages of glomerular function (GF). Those with serum cotinine levels < 3.3 ng/mL and did not report using any tobacco products during the last 5 days were classified as nonsmokers. Those with serum cotinine levels ≥ 3.3 ng/mL and reported using cigarettes, cigars, pipes, and/or water pipes with or without using e-cigarettes and/or smokeless tobacco products during the last 5 days were classified as nonsmokers. Those who had eGFR > 90 mL/min/1.73 m2 were classified to be in GF stage 1 or GF-1, those with 60 ≤ eGFR ≤ 90 mL/min/1.73 m2 were classified to be in GF-2, those with 45 ≤ eGFR < 60 mL/min/1.73 m2 were classified to be in GF-3A, and those with 15 ≤ eGFR <45 mL/min/1.73 m2 were classified to be in GF-3B/4. Among nonsmokers, except for females and non-Hispanic blacks, adjusted levels of serum cotinine (AGM) decreased relatively sharply from GF-1 to GF-2, stayed relatively stable at GF-2 and GF-3A, and then rose moderately to GF-3B/4. For example, for non-Hispanic whites, AGMs were 0.042, 0.033, 0.031, and 0.037 ng/mL at GF-1, GF-2, GF-3A, and GF-3B/4 respectively. Among smokers, except for females and non-Hispanic blacks, AGMs increased relatively sharply from GF-1 to GF-2 and then decreased from GF-2 to GF-3/4. For example, for males, AGMs were 151.9, 192.0, and 162.9 ng/mL at GF-1, GF-2, and GF-3/4 respectively. AGMs for male smokers were lower than for female smokers at GF-3/4 (162.9 vs. 197.2 ng/mL, p < 0.01). The order of AGMs by race/ethnicity was non-Hispanic blacks > non-Hispanic whites > Hispanics and others at every GF stage. AGMs at GF-3/4 were higher than AGMs at GF-1 for smokers.