People who drive commercial vehicles could be incorrectly reporting their symptoms of sleep apnea due to fears of losing their jobs, according to a study presented at the European Respiratory Society's Annual Congress in Vienna, Austria.

People with sleep apnea suffer frequent disruptions to their breathing during sleep, leaving them with headaches, drowsiness and sometimes depression during the day. Obstructive sleep apnea is a well-established risk for traffic accidents.

"Our study suggests that commercial drivers are playing down their levels of sleepiness for fear of losing their jobs," said Dr. Werner Strobel from University Hospital, Basel, Switzerland.

Strobel and his fellow researchers came to this conclusion after examining 37 commercial vehicle drivers with sleep apnea and comparing them with a group of 74 patients with sleep apnea who were not commercial vehicle driver. Both groups had similar characteristics of age, body mass index, and similar numbers of disturbances suffered on average during the night. Both groups also underwent treatment using CPAP.

Levels of sleepiness were then analyzed using the Epworth Sleepiness Score; a well-established short questionnaire used to give levels of sleepiness during the day time. The survey provides a score, which is the sum of eight items and can range between zero and 24. The higher the score, the higher the person's level of daytime sleepiness.

"Both the group of drivers and the group of non-drivers began the study with a similar number of disturbances during the night. You would therefore expect their reports of sleepiness to be similar to begin with. However, the drivers estimated their levels of sleepiness as lower than the non-drivers. This pattern continued throughout the course of the study, with drivers reporting lower symptoms, yet receiving less treatment and making more unscheduled visits to the clinic," Strobel noted.

At the start of the study, commercial drivers reported an average score of 8.1 on the sleepiness scale, compared with an average of 11.0 reported by non-commercial drivers, despite a similar number of disturbances at night between the two groups. The difference was also seen after six months of treatment using CPAP therapy for sleep apnea, with the drivers reporting an average sleepiness score of 4.8 and non-drivers reporting an average of 7.7.

The authors of the study speculate that the lower scores reported by the commercial drivers could be due to drivers under-scoring their sleepiness levels for fear of losing their licenses.