Table 1.

Clinical characteristics of subjects.

Group	N	Age	Years of smoking	Number of cigarettes/day
Nonsmokers	36	53.00 ± 1.20	N/A	N/A
All smokers	63	54.21 ± 0.81	28.79 ± 1.16	18.03 ± 1.15
≥20 cigarettes/day	36	54.72 ± 1.04	30.28 ± 1.18	23.61 ± 1.27
<20 cigarettes/day	27	53.52 ± 1.26	26.81 ± 2.17	10.59 ± 0.88