|  |  | p-value for least significant difference | ||
---|---|---|---|---|---|
 | n (%) | Mean NO2(SD) | Daily | Occasional | Former |
Daily | 1,249 (20.9) | 15.70 (3.24) | Â | Â | Â |
Occasional | 283 (4.7) | 15.52 (3.63) | 0.40 | Â | Â |
Former | 2,127 (35.6) | 15.42 (3.29) | 0.02 | 0.63 | Â |
Never | 2,308 (38.6) | 15.23 (3.19) | <0.001 | 0.16 | 0.05 |