The natural history of light smokers: A population-based cohort study

Among cigarette smokers, lower levels of consumption, defined as smoking fewer cigarettes per day (CPD) or not smoking daily, are becoming more common. The relationship between cigarette consumption and smoking frequency (daily or nondaily) is not well characterized, and the natural history of light smoking (defined here as smoking <= 10 CPD) is poorly understood. We assessed changes in CPD and smoking frequency over time among light smokers (<= 10 CPD) and very light smokers (<= 5 CPD), using a population-based longitudinal survey of 3,083 adult smokers in Massachusetts who were interviewed three times over a 4-year follow-up period (in 2000-2001, 2002-2003, and 2005-2006). We used logistic regression to identify factors associated with light smokers' progression to heavier smoking or smoking reduction/quitting. Seventy percent of very light smokers were nondaily smokers. Very light nondaily smokers differed from very light daily smokers by younger age, higher socioeconomic status, a social smoking pattern, later smoking initiation, less evidence of nicotine addiction, and more recent and planned cessation efforts. Very light nondaily smokers and smokers consuming 6-10 CPD were more likely to remain in the same smoking category and were less likely to increase consumption than were very light daily smokers. Factors independently associated with increasing consumption among very light smokers were smoking daily, nicotine dependence, White ethnicity, social smoking, and having more friends who smoked; among smokers consuming 6-10 CPD, male gender and lack of quitting self-efficacy were associated with increasing consumption. Our findings indicate that most light smoking is not a gateway to heavier smoking.