Our analyses indicated no association between perceived helpfulness of each reported cessation method and duration of quitting.
For duration of quitting, RRs were also expressed relative to current smokers.
For duration of quitting compared to current smoking the number of data sets available are somewhat less than the corresponding number for duration of quitting compared to never smoking.
For duration of quitting compared to current smoking, data are available from one less study than for duration of quitting compared to never smoking for COPD, but from the same studies for CB.
The results are limited by the variability of the categories used by different studies to classify duration of quitting.
Data are too few for emphysema to make inferences for age of starting and duration of quitting.
From the second question, we obtained information on whether the father or mother who quit smoking smoked during pregnancy, by simultaneously looking at the duration of quitting smoking and their child's age.
For the dose-related indices, meta-analyses were conducted for: E amount smoked, F age of starting to smoke, G pack-years, H duration of smoking, I duration of quitting compared to never smokers (or long-term ex smokers), and J duration of quitting compared to current smokers (or short-term quitters).
The number of studies providing usable data for duration of quitting compared to never smoking is seven for COPD, and seven for CB, but none for emphysema.
Table 18 presents results for duration of quitting (vs. never smoking) based on results for smoking of any product (or cigarettes if not available).
