For example, in a recent study among a nationally representative sample in the US, individuals with shorter TTFC had greater tobacco carcinogen levels (creatinine-adjusted urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL)), even after adjustment for other smoking factors [13]. TTFC is also predictive of both plasma and urinary cotinine levels, even after adjustment for the number of cigarettes smoked per day [14]. Recently, we reported that TTFC differentiates lung cancer risk and provides information beyond usual smoking metrics [9]. Furthermore, a recent Canadian study demonstrated that current smokers with COPD had greater odds of high nicotine addiction, as measured by the total FTND score compared to smokers without COPD [7]. This suggests that TTFC may help to quantify disease risk, but no study has yet reported the association between TTFC and COPD.
