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Abstract & Commentary
Synopsis: Over a 5-year period, the incidence of developing sleep-disordered breathing (AHI > 5 events/hr) is about 37%, about 7% per year. With aging, male gender and body mass index (BMI) lose importance as risk factors for obstructive sleep apnea.
Source: Tischler PV, et al. JAMA. 2003;289:2230-2237.
The purpose of the Cleveland Family Study is to determine the incidence, natural history, and risk factors of obstructive sleep apnea (OSA). This report includes longitudinal data for 285 individuals who were considered not to have significant sleep apnea at baseline (apnea plus hypopnea index [AHI] of fewer than 5 events per hour of sleep). At baseline, 72% were women, 21% were black, 16% had cardiovascular disease and/or diabetes, 42% snored, the mean body mass index (BMI) was 27.6 ± 6.4 kg/m2, and the mean age was 36.8 ± 11.9 years. Extensive medical, demographic, and anthropometric data were gathered; in addition, a limited physical examination and some laboratory testing were performed. Subjects in this report all underwent in-home polysomnography (PSG, a.k.a. "Sleep Studies") on 2 occasions about 5 years apart.
The 5-year incidence of developing sleep-disordered breathing (defined in this study as an AHI of > 5 or more events/hr) was 36.7%. With regard to severity for these incident cases of sleep-disordered breathing (SDB), 20.3% had AHIs of 5-9.9 events/hr, 6.3% had AHIs of 10-15 events/hr, and 10.1% had AHIs of more than 15 events/hr. After ordinal logistic regression to adjust for significant covariants, age, BMI, gender, waist/hip ratio (WHR), and serum cholesterol were significantly associated with the AHI. Variables that were not associated with AHI included self-reported cardiovascular disease, diabetes, family history, race, smoking, alcohol ingestion, or tonsillar size. The association of hypertension with AHI was inconsistent. With aging, the risks for SDB changed. After the age of about 50, male gender was no longer a significant risk factor, and after about age 60, BMI was no longer a significant risk factor.
Comment by Barbara A. Phillips, MD, MSPH
These are astonishing findings, any way you look at it. There are several tempering factors (infra vide), but a 5-year incidence of 37% for an AHI that many would consider to be diagnostic of OSA is downright frightening. To put this in context, CMS (Centers for Medicare and Medicaid Services, formerly known as HCFA or Health Care Financing Administration) will pay for continuous positive airway treatment (CPAP) for patients who have an AHI of 5 or more with just about any symptom1 and for asymptomatic patients who have an AHI of 15 or more (which 10% of this population developed over the course of 5 years). Tischler and colleagues carefully skirt the issue of what constitutes OSA, referring instead to "SDB," or to absolute AHIs. This is smart, given that that they used a nonstandard definition of oxygen desaturation for identifying apneas and hypopneas (this study used an oxygen desaturation of 2.5%, instead of the more standard 4%)2 and that AHIs must be correlated with symptoms to make a diagnosis. Even so, a 5-year incidence of 10% (2% per year) for an AHI of 15 events per hour of sleep is alarmingly high, given that the risk of cardiovascular disease is correlated with AHI and is certainly significant at AHIs of 15 events per hour of sleep or more.3
The classic patient with sleep apnea is a 48-year-old, obese, hypertensive man. This study clearly documents that sleep apnea begins to look different after the age of about 50. Gender and obesity become negligible risk factors after the ages of 50 and 60 years, respectively. This has been reported before.4 It is likely that older patients with sleep apnea are being overlooked because they don’t match the classic stereotype; this is really a disservice to senior citizens, since we know that sleep apnea causes so many of the afflictions of older age, such as hypertension,5 cardiovascular disease,3,6 and cognitive decline,7 and that CPAP can reverse these changes.8-10
Some findings of this study contradict earlier reports. This study found no relationship between AHI and self-reported race, cigarette smoking, or alcohol use. These findings are at variance with previous data.11-13 However, the results of a prospective study of incident data such as this one are more powerful than cross-sectional ones. These issues may remain open questions for now.
Take home messages: Sleep apnea is common and becoming more so. Because the "typical" risk factors (obesity, male gender) become much less important in the older patient, we probably are seriously under diagnosing SDB in geriatric patients, and may be missing opportunities to preserve function and quality of life in this age group.
Dr. Phillips, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington, KY, is Associate Editor of Internal Medicine Alert.
2. Meoli AL, et al. Sleep. 2001;24:469-470.
3. Shahar E, et al. Am J Respir Crit Care Med. 2001;163:19-25.
4. Young T, et al. Arch Intern Med. 2002;162:893-900.
5. Peppard PE, et al. N Engl J Med. 2000;342:1378-1384.
6. Peker Y, et al. Am J Respir Crit Care Med. 2002;166:159-165.
7. Kim H, et al. Am J Respir Crit Care Med. 1997;156:1813-1819.
8. Pepperell JC, et al. Lancet. 2002;359:204-214.
9. Engelman HM, et al. Am J Respir Crit Care Med. 1999;159:461-467.
10. Kanedo Y, et al. N Engl J Med. 2003;348:1233-1241.
11. Redline S, et al. Am J Respir Crit Care Med. 1997;155:186-192.
12. Wetter DW, et al. Arch Intern Med. 1994;154:2219-2224.
13. Block AJ, et al. Am J Med. 1986;80:595-600.