The initial sample was sized to ensure the statistical power needed to test primary and secondary aims of the study [21 (link)]. Consistently, the reduction for each participant has been calculated taking into account the difference between the number of cigarettes smoked per day at the baseline and at 1-year. Changes in smoking status and frequency of respiratory symptoms were evaluated by the use of Chi-squared test. Participants were included into three groups based on their smoking status (Abstinent, Reduced consumption or No change). We defined abstinence as self-reported complete absence of tobacco cigarette use over the previous month. Thus, the abstinent group included who reported continuous abstinence over the previous month. This status was also controlled at month 6 and 12 by the use of eCO level, that must be under or equal 7 ppm. The reduction group included smokers that reported at least a 20% decrease in daily tobacco consumption compared to the baseline. All the other participants were considered current smokers with no status change. An Intention-to-treat analysis (ITT) was used. Mix-designed ANCOVA tests were used to evaluate significant changes in CO, Dependence Level, LCQ, and HADS. SPSS package (version 26.0, IBM, Chicago, IL, USA, 2019) was used.
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