Increased Physician-Reported Sleep Apnea: The National Ambulatory Medical Care Survey
Abstract & Commentary
Synopsis: In this retrospective analysis of the National Ambulatory Medical Care Survey (NAMCS) from 1990-1998, Namen and colleagues found a 12-fold increase in the diagnosis of sleep apnea among outpatients. Sleep apnea reporting was greatest among primary care providers (37%), pulmonologists (24%), and otolaryngologists (18%).
Source: Namen AM, et al. Chest. 2002;121:1741-1747.
The incidence of sleep apnea (SA) in middle-age adults is 2-4% and higher among the elderly. SA puts the patient at risk for heart disease, hypertension, increased mortality, increased motor vehicle accidents, and increased work-related injuries. These consequences, along with their additional health care costs, have highlighted the need for increased physician recognition of SA. However, it has been reported that only 10% of patients with clinically significant SA are recognized. A national consensus panel recommended that efforts be made to educate physicians in order to improve detection of the disease. These have included increased hours of medical education dedicated to sleep-disordered breathing, and advertisements and increased reports in the lay press and medical literature. It is not known whether this has led to any change in the frequency with which physicians diagnose SA. The purpose of this study was to assess changes in the number of patients per year in whom physicians report SA, what specialties are more likely to report SA, and what the demographics are of patients in whom SA is reported.
To acquire the data, Namen and associates searched the National Ambulatory Medical Care Survey (NAMCS). NAMCS is a national survey of office-based physicians conducted by the National Center for Health Services and the Centers for Disease Control and Prevention. The survey contains data on individual outpatient office visits and is then weighted to reflect national estimates. Data regarding patterns of disease reporting, disease-specific patient characteristics, and diagnosis are available. The data set from 1990-1998 contains 372,830 records and provides a weighted estimate representative of 6.2 billion patient visits. The patients could further be stratified by physician specialty. The database was searched for all diagnostic codes used to describe SA. Among patients with the diagnosis, a further analysis was conducted regarding other diagnosis, patient age, and gender. In addition, a search for any other primary sleep disorder was conducted. To assess for changes in the frequency of SA reported in the medical literature, a librarian blinded to NAMCS data surveyed MEDLINE and the Science Citation Index for the years 1990-1998. The trend in the number of accredited sleep laboratories from 1990-1998 was acquired from the database of the American Academy of Sleep Medicine.
During the 9-year period, there was a 12-fold increase in the number of SA diagnosis reported per year (from 110,000 diagnosis/yr to 1.3 million [P < 0.0001]). In contrast, the frequency of common diseases such as upper respiratory tract infection (URI), hypertension (HTN), and diabetes mellitus (DM) did not significantly change (mean reporting frequencies: URI, 65 million/yr; HTN, 52.2 million/yr; DM, 69 million/yr). The frequency of reporting parasomnias, restless leg syndrome, and narcolepsy did not significantly change, but the frequency of insomnia diagnoses increased 4-fold (from 801,862 diagnosis/yr to 2,686,006 (P < 0.001]).
The patients diagnosed were predominately male (71%) and white (89%). Most diagnoses were made from the ages of 30-69 (84%), with a peak in the 40-49 year age group (33%). Comorbidities included cardiovascular disease (16%), pulmonary disorders such as COPD, asthma and respiratory distress (13%), and obesity (6%). When stratified according to physician specialty, nearly 80% of SA was reported by 3 groups of physicians. Primary care providers (internal medicine, family practice, pediatrics) accounted for 37%, pulmonologists 24%, and otolaryngologists 18%. This distribution did not change over the 9-year period.
During the period from 1992-1996, there was a more than 50% increase in the number of publications regarding SA (from 202 articles per year to 344) cited in MEDLINE. The Science Citation Index revealed a 21-fold increase (data not shown) in the number of references to SA publications from 1990-1998. There was a strong association between the number of SA diagnoses and the number of SA publications (RR = 0.93, P < 0.001), the number of references to sleep publications (RR = 0.97, P < 0.001) and the number of sleep laboratories (RR = 0.90, P < 0.001) during 1990-1998.
Comment by David Ost, MD & Charles Scott Hall, MD
SA is a common disorder with serious sequelae. It has been estimated to be as common as asthma1 and adds billions of dollars to health care costs.2 One report estimated the prevalence in middle aged adults to be 2% with less than 10% of patients with SA actually diagnosed.3 There clearly needs to be increased physician awareness of SA and the results of this study by Namen et al are encouraging. Even though these data are based on weighted estimates that may overestimate or underestimate an effect and the overall rate of reporting is still low, there is clearly a trend toward increased diagnosis and awareness of SA. The relationships between SA diagnosis and the medical literature and sleep laboratory availability, while intriguing, do not indicate cause and effect.
Dr. Ost, Assistant Professor of Medicine, NYU School of Medicine, Director of Interventional Pulmonology, Division of Pulmonary and Critical Care Medicine, Northshore University Hospital, Manhasset, NY, is Associate Editor of Internal Medicine Alert. Dr. Hall is a Fellow in Pulmonary and Critical Care Medicine, North Shore University Hospital-NYU School of Medicine, Manhasset, NY.
References
1. Young T, et al. N Engl J Med. 1993;328:1230-1235.
2. Wake up America: A National Sleep Alert. Vol 2. Bethesda, MD: National Commission on Sleep Disorders Research; 1995.
3. Young T, et al. Sleep. 1997;20:705-706.
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