A pair of new studies find that smokers take many more sick days annually than nonsmokers and perform worse when they are on the job, Bloomberg News reported March 29.

A Swedish study by Petter Lundborg and colleagues from Free University of Amsterdam found that smokers took an average of 34 sick days per year, compared to 20 per year for people who never smoked and 25 per year among former smokers.

Sweden has one of the highest rates of sickness absence in the industrialized world; in the U.S., the average worker takes off nine days annually for illness. "The results suggest that policies that reduce and/or prevent smoking may also reduce the number of days of sick leave," wrote Lundborg.

In a study of women in the U.S. Navy, San Diego State University researcher Terry Conway and colleagues found that smokers were more likely to be discharged for medical reasons, bad behavior, misconduct, drug misuse and personality disorders. Smokers also were more apt to resign from the Navy before serving their full terms, and were paid less.

However, noted Conway, "Cigarette smoking might simply be a marker for other underlying factors such as nonconformity and high risk-taking, that contribute to poorer performance."

The research was published in the journal Tobacco Control.