Sleep apnea is a common condition that occurs due to an obstruction in airflow into the lungs during sleep. The disorder is characterized by episodes in which the patient stops breathing temporarily, sometimes several times throughout the night.
Kingman P. Strohl, co-author of the study, and his colleagues gave 744 adult patients from five primary care sites in Cleveland the Berlin Questionnaire, which was developed by the Conference on Sleep in Primary Care in April 1996.
The questionnaire asks patients to determine the frequency and severity of signs seen in sleep apnea, such as snoring and daytime sleepiness. In addition, it asks questions regarding high blood pressure and obesity, known risk factors for the development the disorder. The results of the study are published in the Oct. 5 issue of Annals of Internal Medicine.
Of the 744 patients who filled out the questionnaire, 279 were classified as being at high risk for the disorder. Subsequent sleep studies showed that 46% actually did have it. No doctor at any of the five practices had referred more than two patients for further sleep evaluation in the past year.
Strohl and his fellow researchers also found that more than a third of the primary care patients involved in the study reported risk factors for sleep apnea -- high blood pressure and obesity. And almost 5% of them reported being drowsy while driving more than three times per week. However, the authors write, primary care physicians often do not ask patients about the symptoms, and therefore sleep apnea frequently goes undiagnosed.
Determining who should take the questionnaire "probably should be decided on the basis of symptom severity. Four percent of the respondents in this survey said that they were drowsy [while driving] every day of the week. And only 50% of those had symptoms of sleep apnea. Perhaps this is the group to focus on because of the societal and professional risks they pose," Strohl tells WebMD. Strohl is a professor of medicine at Case Western and director of the university's Center for Sleep Education and Research.
In an editorial that accompanies the study, Richard P. Millman, MD, stresses that physicians and patients need to be educated about sleep apnea. Millman is director of the Sleep Disorders Center at Rhode Island Hospital in Providence and a professor at Brown University School of Medicine. He maintains that primary care physicians can correctly refer high-risk patients for sleep testing if only they ask the right questions. At Rhode Island Hospital, Millman notes, sleep apnea was confirmed with all-night sleep studies in 96% of the 68 patients referred by their primary care physicians.
"This well-designed study shows that a simple self-administered patient questionnaire is an excellent way of identifying patients who are at high risk for sleep apnea and who might benefit from sleep testing for that condition. It implies that the prevalence of obstructive sleep apnea is probably higher than previously considered by earlier studies," writes Millman.
The authors stress that more studies on the questionnaire need to be conducted, and that even though it may be effective, a physician is still needed to begin a treatment plan.
This research was supported in part by grants from 3M Inc. and the National Institutes of Health.