BERLIN QUESTIONNAIRE FOUND TO BE EFFECTIVE IN SPECIFYING RISK FOR SLEEP APNEA

CLEVELAND-New findings support the efficacy of the Berlin Questionnaire, the first sleep apnea screening survey designed specifically for use in primary care settings.¹ "We think the questionnaire is a reasonable starting point for primary care physicians to begin to think about sleep apnea," said Kingman P. Strohl, MD, one of the study authors, in a recent interview with Respiratory Reviews.

Richard P. Millman, MD, wholeheartedly agrees. "This well-designed study shows that a simple, self-administered patient questionnaire is an excellent way of identifying patients at high risk for sleep apnea who might benefit from sleep testing for that condition," he wrote in an editorial.² Dr. Millman is with the Division of Pulmonary, Sleep, and Critical Care Medicine at Rhode Island Hospital in Providence.

The questionnaire was "the outcome of a consensus conference [Conference on Sleep in Primary Care, April 1996] between primary care physicians and pulmonary specialists, which took place in Berlin, Germany," explained Dr. Strohl, a professor of medicine, physiology, biophysics, and anatomy at Case Western Reserve University in Cleveland. As part of those proceedings, 120 German and American primary care and pulmonary physicians chose questions from the literature about sleep apnea risk factors. The result was a 14-item screening tool designed to ferret out the presence of such sleep apnea symptoms as snoring, daytime sleepiness, and drowsiness when driving. That information was then correlated with patient-specific data on age, gender, ethnicity, height, weight, neck circumference, and blood pressure.

To simplify sleep apnea screening, the physicians distinguished between high- and lower-risk patients. High-risk patients had to have persistent (more than three or four times a week) sleep apnea symptoms and hypertension. Those without persistent symptoms or only one sleep apnea symptom were considered to be at lower risk.

The study authors evenly divided 1,000 Berlin Questionnaires among five primary care physicians at five sites in the Cleveland area. All five physicians belonged to a hospital-owned network, were board-certified in internal medicine, and had been practicing primary care medicine for more than 4 years. "According to network records, no physician had referred more than two patients for sleep studies in the previous year," noted the authors in their published report.

Office staff gave the questionnaires to consecutive patients who visited the physicians for any reason. To be included in the analysis, completed questionnaires had to be dated, with the date falling within 3 weeks of distribution, and had to be returned to the study authors within 1 month of completion.

Sleep apnea symptoms were prevalent among the 744 questionnaire respondents. Indeed, 47.9% snored (often louder than normal speech) at least three or four times a week, 38.8% had daytime fatigue, 5.2% had breathing pauses during sleep observed by others, and 4.4% nodded off while driving. Other respondents had these symptoms as well, although somewhat less frequently.

"Overall, about 30% of respondents had two or more signs or symptoms suggesting obstructive sleep apnea," Dr. Strohl told Respiratory Reviews. More men than women were found to be at high risk (44.5% vs 33%; P<.002).

Using an alphabetical list, the authors contacted the first 75 high-risk patients and the first 65 low-risk patients and asked them to participate in home sleep studies with a portable monitor. The monitor measured nasal and oral airflow, chest wall movement, oxygen saturation (SaO₂), and pulse rate during sleep.

For measurements to be acceptable, patients had to be in bed at least 6 hours and achieve good to excellent respiration and SaO₂. The study authors defined a respiratory disturbance as a decrease in nasal or oral airflow (alone or with chest wall movement) of about 50% for 10 seconds or more. An SaO₂ decrease of 4% or greater was considered a significant oxygen desaturation.

The researchers measured the number of respiratory disturbances per patient per hour of sleep to determine the respiratory disturbance index (RDI). In addition, they counted the number of SaO₂ decreases of 4% or greater per hour of sleep to determine the oxygen desaturation index.

One hundred respondents (69 high-risk and 31 low-risk) took part in the home sleep studies. A much higher mean RDI and oxygen desaturation index were found in the high-risk group than in the lower-risk group (21.1±18.5 vs 4.7±7.0, respectively, for mean RDI; 19.4±19.5 vs 5.9±7.6, respectively, for mean oxygen desaturation index).

Risk grouping was useful in predicting an RDI greater than 5--a strong indicator of sleep apnea. "For example, being in the high-risk group predicted an RDI greater than 5 with a sensitivity of 0.86%, a specificity of 0.77%, a positive predictive value of 0.89%, and a likelihood ratio of 3.79," reported the study authors. Similarly, being in the lower-risk group was highly predictive of an RDI less than 5.

This study also shows that primary care physicians underrecognize sleep apnea, Dr. Millman noted in his editorial, citing sparse sleep apnea referrals among the study physicians. "The real problem," he explained, "is a lack of education at all levels about sleep disorders. Physicians have been shown to receive, on average, a total of only 2.1 hours of formal education in sleep medicine during their medical school training."³ He, therefore, recommended increased training in the recognition of sleep disorders in medical school, residency, and postgraduate education.

Although the Berlin Questionnaire appears valid, more work is necessary. "I think the questionnaire needs to be verified in other settings," said Dr. Strohl, noting that there are plans to test it in different regions of the United States as well as in other countries.

-Timothy Begany

References
1. Netzer NC, Stoohs RA, Netzer CM, et al. Using the Berlin Questionnaire to identify patients at risk for the sleep apnea syndrome. Ann Intern Med. 1999;131:485-491.
2. Millman RP. Do you ever take a sleep history? [Editorial]. Ann Intern Med. 1999;131:535-536.
3. Rosen R, Mahowald M, Chesson A, et al. The Taskforce 2000 survey on medical education in sleep and sleep disorders. Sleep. 1998;21:235-238.