Cigarette smoking is a well-known risk factor for chronic obstructive pulmonary disease (COPD), a group of lung diseases that includes emphysema and chronic bronchitis. But few studies have looked at whether other types of smoking contribute to COPD as well.

In the new study, researchers found that among more than 3,500 U.S. adults, those who had ever smoked cigars or pipes were more likely than non-smokers to show obstructed airflow - a hallmark of COPD -- during tests of lung function.

Of the 56 study participants who said they had smoked at least 20 cigars or pipe-bowls in their lives, 18 percent showed airway obstruction. That compared with less than 8 percent of men and women who had never smoked.

When the researchers weighed other factors -- like age and history of cigarette smoking -- cigar and pipe smoking were linked to a doubling in the odds of airflow obstruction.

The findings suggest that pipe and cigar smoking produce a measurable increase in the risk for COPD, the investigators report in the Annals of Internal Medicine.

Physicians should consider pipe and cigar smoking a risk factor for COPD and counsel their patients to quit, senior researcher Dr. R. Graham Barr, an assistant professor at Columbia University Medical Center in New York, said in a news release from the journal.

The findings add to evidence of the serious health risks of cigars and pipes, which many people tend to view as safe ways to smoke. Cigar and pipe smoking have been linked to increased risks of mouth and throat cancers, heart disease and lung cancer. One study estimated that those risks were on par with those associated with light cigarette smoking (defined in the study as up to 19 cigarettes per day).

One reason that people often regard pipes and cigars as safer smoking alternatives is their belief that the smoke is not inhaled into the lungs, according to an editorial published with the study.

But research shows that belief is incorrect, write Drs. Michael B. Steinberg and Cristine D. Delnevo of the University of Medicine and Dentistry of New Jersey in New Brunswick.

The current study, they add, offers further evidence that smokers of these products are exposed to sufficient levels of toxins to affect their lung health.

The findings are based on questionnaires and lung-function tests given to more than 3,500 U.S. adults ages 48 to 90. Overall, 9 percent said they had smoked at least 20 pipe-bowls in their lives, while 11 percent had smoked at least 20 cigars. Just over half had ever smoked cigarettes.

Study participants who had only smoked cigars or pipes -- that is, cigarette-free -- generally had poorer scores on their lung-function tests and were twice as likely to show airflow obstruction as people who had never smoked.

The effects were compounded among people who had smoked cigarettes as well; their risk of airflow obstruction was increased more than three-fold. Among the 428 study participants who had smoked both cigarettes and cigars or pipes, 21 percent had obstructed airways.

The findings are particularly important in light of the fact that cigars and pipes are still often seen as emblems of sophistication, affluence, education and celebration, according to Steinberg and Delnevo.

These images, they write, largely fostered by the tobacco industry, perpetuate the idea that these products play a suitable role in our society.