Research Article
Using the Negative Exponential Model to Describe Changes in Risk of Smoking-Related Diseases following Changes in Exposure to Tobacco
Table 1
Summary of lung cancer results for reducing amount smoked from three prospective studies.
| Characteristic | Study 1 [148] | Study 2 [149] | Study 3 [150] |
| Location | Denmark | Norway | Korea |
| Sex | M and F combined | M, F | M |
| Time between the two examinations (years) | 5 to 10 | 3 to 13 | 2 |
| Follow-up period from examination two (years) | 18 | 21.2 | 10.7 |
| Definition of a continuing smoker ( subjects) | Heavy smoker (at least 15 cigs/day) at each exam ( 7351) | Heavy smoker (at least 15 cigs/day) at each exam ( 4739M, 1831F) | At each exam subjects were described as heavy (20+, 57730), moderate (10–19, 101347), or light (<10 cigs/day, 76754) |
|
Definition of a reducing smoker ( subjects) | () Heavy smoker at first exam reducing by at least 50% at the second exam ( 832) | () As for study 1, males ( 348) | () Heavy smoker at first exam reducing to moderate smoker at second exam ( 15936) | | () As for study 1, females ( 127) | () Heavy to light ( 4293) | | | () Moderate to light ( 19168) |
| Ratio of average consumption at the two exams in reducers () | () 8.5/20.2 = 0.42 | () 9.7/22.9 = 0.42 | () 0.50 | | () 8.6/19.5 = 0.44 | () 0.17 | | | () 0.33 |
| Time from reduction to end of follow-up (years)a | 21.4 | 24.0 | 11.7 |
| Cases in reducers | () 52 | () 10 | () 63 | | () 2 | () 95 | | | () 53 |
| Average age at the time of reduction (years) () | () 49.0 | () 39.0 | () 42.6 | | () 38.2 | () 42.9 | | | () 42.4 |
| Observed RRs (95% CIs)b | () 0.73 (0.54–0.98) | () 0.71 (0.36–1.39) | () 0.72 (0.59–0.89) | | () 0.51 (0.12–2.08) | () 0.63 (0.46–0.86) | | | () 0.79 (0.64–0.98) |
| NEM predicted RRs | () 0.64 | () 0.60 | () 0.80 | | () 0.61 | () 0.67 | | | () 0.73 |
|
|
Estimated as the time of follow-up plus half the time between the two examinations. Reducers relative to continuing smokers.
|