Urinary cotinine levels (≤50 ng/mL vs >50 ng/mL) by reported cigarette use on study day, n (%)
| 2016–2017 study* | |||
| February 2017, n=81 | Overall | ≤50 ng/mL | >50 ng/mL |
| Smoked cigarette(s) | 4 (5%) | 2 (50%) | 2 (50%) |
| Did not smoke | 77 (95%) | 61 (79%) | 16 (21%) |
| 2017–2018 study* | |||
| January 2018, n=92 | Overall | ≤50 ng/mL | >50 ng/mL |
| Smoked cigarette(s) | 1 (1%) | 0 (0%) | 1 (100%) |
| Did not smoke | 91 (99%) | 67 (74%) | 24 (26%) |
| April 2018, n=167 | Overall | ≤50 ng/mL | >50 ng/mL |
| Smoked cigarette(s) | 10 (6%) | 2 (20%) | 8 (80%) |
| Did not smoke | 157 (94%) | 117 (75%) | 40 (25%) |
*Survey question: ‘how many cigarettes have you smoked since you woke up this morning?’.