Characteristics of subjects

NonsmokersSmokers
Number1516
Age
 Mean34.4  ± 9.638.4  ± 10.6
 Range21–5818–60
Males/females8/710/6
Years smoking
 Mean20  ± 11
 Range8–35
Smoking dose, pack per day
 Mean1.10  ± 0.36
 Range0.5–2
Time between last cigarette and PET scan, h
 Mean2.7  ± 2
 Range2–9.5