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Article #77

Gastroesophageal reflux disorder affects about 5% of the population. It arises from backward flow up into the esophagus of acidic stomach contents, causing pain and burning. Since this can happen in normal people, parameters are set to define the threshold of disease. Moreover, in normal people, unlike those with the disease, gastroesophageal reflux rarely happens at night. When it does occur at night, it usually lasts longer than when during the day. Some people report awakening with symptoms, but it has remained unclear whether the reflux symptoms caused the arousal, or vice versa. Others seem able to sleep through these events. In patients with sleep apnea, the negative pressures generated in the chest to overcome obstructions may trigger reflux. In fact, CPAP has been found to reduce the acidity of esophageal contents.      Fifteen patients suspected to have OSA on the basis of snoring, excessive daytime sleepiness, and at-home sleep recording, were included in this study, without regard to presence or absence of reflux symptoms. These were assessed after intake.      Ages ranged from 34 to 66 years, averaging 51 years. All were obese, with Body Mass Indices ranging from 25 to 40, averaging 32. Apnea Hypopnea Indices ranged from 0.6 (1 case) to 100 respiratory events per hour, thus spanning the range of apnea severity from normal to severe. but averaging 30 (moderately severe). Only 5 patients (33%) reported symptoms of reflux.      All patients received laboratory sleep studies concurrent with continuous measurement of esophageal acidity, which went on for an entire 24 hours. This record was considered pathological if pH fell below 4 for more than 10.5% of the time spent in an upright position, or 6% in a lying position. An event was labelled a reflux if pH stayed below 4 for at least 30 seconds.      On average, patients experienced 265 arousals, including 26 awakenings, during the course of the night. Respiratory events preceded, on average, 78% of the arousals and 58% of the awakenings.      During the daytime, all patients showed evidence of reflux, four to a pathological degree. At night, eight patients--only three of whom reported nocturnal reflux symptoms--had a total of 69 reflux events.      About half of these reflux events occurred with the patient awake, while the remainder were followed within a minute by arousal or awakening. In only one instance did sleep continue without interruption or disruption by the reflux event. No relationship appeared between respiratory events and reflux events.      Pathological reflux appeared to be more common in this sample of sleep apnea patients than in the general population. Also, it occurred without some patients' awareness of symptoms. Though reflux events often took place while patients were awake (after initial sleep onset), when reflux occurred while asleep it almost always seemed to result in arousal or awakening. No relationship between respiratory and reflux events occurred to support the theory that the negative pressures associated with obstructed breathing caused the reflux. Most of the far more frequent respiratory events resulted in no reflux.      An alternative explanation for the high frequency of reflux in these apnea patients may lie in the association of both reflux and apnea with obesity.

In one respect, this small study serves to remind us to avoid the tempting fallacy of assuming that, because one disorder, such as sleep apnea, shows an association with another, such as gastroesophageal reflux, the two must have some cause-and-effect relationship to each other. It is quite possible for an observed association of two disorders to result from each having a causal relationship of its own with a different condition, such as obesity. Similar fallacies can arise if we fail to consider other "intervening variables," such as age or sex, which may create a spurious association between other disorders.       However, aside from the basic intellectual point it teaches, this study does serve to illustrate a clinical point which I have thought worth emphasizing. The point is that sleep continuity--or its opposite, fragmentation--is the end result of a wide range of factors, even in sleep apnea patients where the respiratory events may appear, at least before treatment, as the predominant influence.      Once apnea is eliminated or much reduced, these other factors may play a larger role in the disruption of sleep, and the sometimes puzzling persistence of symptoms like excessive daytime sleepiness without enough respiratory events to explain them.      As with apnea itself, reflux may go unnoticed by the patient even when it causes arousals. These reflux events and related arousals, moreover, may go much more often unnoticed by a bed partner as well.      To simplify the moral of the tale, you might remind yourself that "Just because you have sleep apnea, this doesn't mean that you're immune to all the many other things that can disrupt your sleep without youre awareness!"

"Breath's a ware that will not keep. Up, lad; when the journey's over There'll be time enough for sleep." A.E. Housman, 1859-1936

 

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