Abstract & Commentary
Comment by Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington, KY, and Associate Editor, Internal Medicine Alert.
Synopsis: In women, obstructive sleep apnea appears to be associated with idiopathic edema, even after controlling for obesity.
Source: Blankfield RP, et al. Sleep Medicine. 2004;5:583-587.
This was a prospective study of patients from 2 private family practice offices in Ohio. A single physician recruited consecutive edematous obese patients to participate; nearly agreed. He also recruited nonedematous patients to serve as controls, about half of whom agreed to participate. Edema was defined as bilateral, pitting, pretibial swelling. Exclusion criteria included an ejection fraction of less than 50%, poorly controlled asthma, documented lung disease, hypoalbuminuria, proteinuria, pregnancy, nonambulatory state, cardiac disease, use of calcium channel blockers, unilateral edema, myxedema, or idiopathic cyclic edema. History and physical examination, spirometry, and overnight polysomnography (sleep studies) were done using established techniques.
Blankfield and colleagues enrolled 44 patients with edema and 34 without. Most of the edema was an incidental finding, not a chief complaint. The edematous patients were heavier (body mass index [BMI], 47.0 vs 36.5), sleepier (Epworth Sleepiness Score, 11.2 vs 5.7), and more likely to be smokers (58 vs 15%). They also had more severe sleep apnea (apnea-hypopnea index [AHI], 34.1 vs 17.0), lower waking oxygen saturation (96.2 vs 97.1%) and slightly worse pulmonary function.
After logistic regression to adjust for BMI, 63% of edematous women had sleep apnea (using an AHI > 15 as the criteria for diagnosing sleep apnea), but only 25% of the nonedematous women did (P = 0.02). A similar difference in the likelihood of sleep apnea in edematous vs nonedematous men did not emerge, probably because the numbers of men were too small.
In a companion article, Blankfield et al found that of 8 men and women with sleep apnea and edema who complied with nasal continuous positive airway pressure, seven experienced a reduction in their edema, a result that was statistically significant.1 The results of the second article indicate that sleep apnea can cause leg edema.
Comment
Lower extremity edema is a common finding in clinical practice. It is particularly prevalent in women. In fact, in a study of women attending a fracture clinic or their general practitioner, 28% and 33%, respectively, experienced non-menstrually related swelling symptoms in the month prior to interview.2 Blankfield et al found that affective symptoms, a family history of swelling, and a BMI > 25 kg/m2 were significantly associated with the presence of mild-to-severe swelling symptoms. Obesity is clearly a major risk factor for edema, and in obese patients the edema is often attributed to the obesity. Blankfield et al had previously noted3 an association between edema and sleep apnea, but had been unable to control for obesity, a problem they rectified to some extent in the current paper. Although edematous patients were indeed heavier than nonedematous patients in this study, the association between edema and sleep apnea persisted even after controlling for obesity.
Why should sleep apnea be associated with edema? Clearly, sleep apnea is prevalent in heart failure,4 but the edematous patients in this study had normal left ventricular ejection fractions. It is, of course, right heart failure that is associated with peripheral edema, and we really don’t know about right ventricular function in these folks. There is a fair body of evidence to suggest that sleep apnea impairs right ventricular function and raises pulmonary artery pressures.5
What does this mean to us in clinical practice? When confronted with a person (especially of the female persuasion) with idiopathic edema, consider the possibility that she might have sleep apnea. It’s treatable, and treatment improves multiple outcomes.
References
1. Blankfield RP, et al. Sleep Med. 2004;5:589-592.
2. Dunnigan MG, et al. QJM. 2004;97:755-764.
3. Blankfield RP, Zyzanski SJ. J Fam Pract. 2002;51: 561-564.
4. Mansfield DR, Naughton MT. Minerva Med. 2004;95:257-280.
5. Marrone O, Bonsignore M. Sleep Med Rev. 2002;6: 175-193.
In women, obstructive sleep apnea appears to be associated with idiopathic edema, even after controlling for obesity.
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