In the study, which covered 300 full-time employees at an airline reservations office, smokers called in sick an average of four days over a three-month period, with former smokers calling in sick 2.4 times and people who had never smoked calling in sick 1.3 days over the same time period.

Employees also completed a questionnaire that assessed their own view of their productivity level as well as how productive they thought their supervisors and co-workers would rate them. Investigators also assessed more objective levels of productivity such as the number of reservations made and the amount of time the reservations agent was unavailable between calls.

Analysis of objective productivity measures showed no significant differences among the three groups, but trends indicated greater productivity among former versus current smokers and increased productivity with time since smoking cessation, according to the study, which was published in the September issue of the journal Tobacco Control.

The study was funded by GlaxoSmithKline, a pharmaceutical company that makes the anti-smoking drug Zyban.