More importantly, the epidemiological studies also show there is a fourth group of smokers, consisting of the majority of smokers (≈70%) [4], [5], [12], who maintain normal or near normal lung function.
In the analysis restricted to never and former smokers (consisting of 755 participants and 1,737 individual observations), we found fairly similar results (see Supplemental Material, Figure S2).
The cancer-non smoker group consisted of 16 samples and the cancer-smoker group had 24 samples.
Further, the COPD cohort tended to be older, with more male participants, whereas the non-smoker group consisted of proportionally more females.
In our analysis, we compared current smokers to non-current smokers, a group which consisted of both former and never smokers; the same measure was used in at least two other studies [ 4, 5].
For smokers, personalised information consisted of 1) quitting smoking now you can recover properly from TB, and 2) as soon as you quit, your coughing and sputum will decrease.
Most notably, similarly to previous reports [ 7, 23], the difference between healthy volunteers and lung cancer patients was still present irrespectively whether the control group consisted of smokers or non-smokers.
The patients were divided into three groups: Group S; consisted of smokers, Group SHS; consisted of exposure smokers, and Group NS; consisted of individuals who did not have any history of smoking and were not exposed to smoke.
Study participants were mostly men and consisted of never smokers (32.5%), occasional smokers (4.5%), and ex-smokers (63%).
Approximately one-third of each population consisted of smokers.
