Contrary to some reports, scuba divers do not appear to have an accelerated decline in lung function, according to researchers at the German Naval Institute.

"Obstructive changes in lung function have been reported with cumulative scuba diving exposure," Dr. Kay Tetzlaff, of the University of Tuebingen, and colleagues write in the medical journal Chest.

To look into this, the researchers studied in 468 military scuba divers and a comparison 'control' group of 122 military submariners, all of them men. Specifically, the team tracked the participants' decline over time in lung performance -- measured as the maximum volume of air expired in 1 second (called the FEV1).

Tetzlaff's group conducted the tests in all of the subjects on at least three occasions over a period of at least 1 year. The average follow-up was 5 years.

At the start of the study, the lung function of divers and controls was greater than the expected norm. Over the study period, no significant difference in the decline of FEV1 was observed between divers and controls.

Forty-three percent of divers and 33 percent of controls reported a history of smoking, and the investigators found that FEV1 decline was significantly more rapid in smokers than in non-smokers.

The drop-off was also greater in subjects with above-average FEV1 to begin with, and in those who were above the average age of the group.

"It is worth mentioning that in the present study the most rapid decline in FEV1 was found in smoking divers with a baseline FEV1 above average," Tetzlaff's team notes.

The investigators conclude that "in healthy males with normal lung function and an uneventful diving history, there are no long-term deleterious respiratory effects. This may be reassuring for millions of recreational divers worldwide," they add.