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What determines whether smokers cut down or quit?


For smoking reduction and cessation strategies it would be helpful to know which characteristics (of smokers, their habits, lifestyles, etc.) are most likely to determine whether smokers successfully quit or reduce the amount they smoke. This study aims to determine predictors of spontaneous smoking reduction and cessation in moderate and heavy smokers.

Bottom line

Impaired lung function and amount smoked were among the predictors of smoking reduction and cessation.


NS Godtfredsen et al. Predictors of smoking reduction and cessation in a cohort of Danish moderate and heavy smokers. Preventive Medicine 2001 33: 46-52.


Participants were 3,791 moderate and heavy smokers (2,173 men and 1,618 women) from the Copenhagen City Heart Study who attended two examinations, in 1976 and 5 years later. Questionnaires collected information on smoking habits at baseline and follow-up. Other health-related measures taken included body mass index and lung function. Participants smoked more than 15 g tobacco a day (moderate smokers 15-24 g and heavy smokers 25 g or more; one cigarette = 1 g). Smoking reduction was defined as a decrease in daily tobacco consumption of 10 g a day or more. Participants who reported reduced smoking or smoking cessation were compared with those who continued their habit unchanged.


Of the 3,791 initial participants, 2,542 completed the follow-up (851 died and 398 dropped out). Their average age was 52 years.

After 5 years, 9% of men and 7% of women had stopped smoking; 13% of men and 9% of women had reduced their smoking.

Smoking reduction , in men and women, was associated with high tobacco consumption (25+ g/day) and severely impaired lung function (FEV1 less than 50% predicted). In men, additional predictors included older age (60 years+) and being overweight; and in women, living alone and smoking other types of tobacco (apart from cigarettes).

Smoking cessation , in men and women, was associated with a tobacco consumption of 15-24 g/day and impaired lung function. Men who inhaled smoke were less likely to quit; women who smoked without filters were less likely to quit. Additional predictors of smoking cessation in women included being overweight, having at least 12 years of education and smoking other types of tobacco (apart from cigarettes).

No associations were observed between smoking reduction or cessation and symptoms of chronic obstructive pulmonary disease or alcohol consumption.


The overriding limitation of this study is the small number of participants in each of the groups (ranging from as few as 4 to 213). Further associations may have been found with larger sample sizes (or indeed, some of the associations observed here could turn out to be spurious).

The reasons why smokers reduce the amount they smoke or quit are complex and it is difficult to make any suggestions from this paper when the results are open to question.

This paper investigated only a few possible predictors of smoking reduction and cessation. Other likely candidates include becoming pregnant, being diagnosed with a serious medical condition and rehabilitation after surgery. Understanding which characteristics of smokers most likely determine whether they will quit or reduce their habit, as well as the times in their lives when they are most likely to do so, is invaluable in order to successfully help smokers change their behaviour.