Fig. 2
Cumulative lung cancer mortality risk of a nonsmoker and continuing smoker. Data of risk were from Doll et al [20]. The continuing smoker’s age corresponding to that of a nonsmoker was calculated from the coefficient of the aging effect and the lag time (Fig. 1), and age at starting smoking. a Smoking started at age 11; b Smoking started at age 18. Solid line, nonsmoker; dashed line, continuing smoker. It should be noted that these figures demonstrate the smoking effect as additional aging effect during the smoking period and do not predict the risk in a very old person. It is known that cancer risk in the very old is often lower than that predicted by various cancer models. The sextic regression equation obtained from the risk in a nonsmoker and continuing smoker starting at age 18 together was: y = − 5.096171 × 10− 10 x 6 + 1.983542 × 10− 7 x 5 − 3.006177 × 10− 5 x 4 + 2.309032 × 10− 3 x 3 − 0.0953864x 2 + 2.014889x − 17.00096