Purpose: In general, clinical acid reflux sleep studies focus on nocturnal symptoms, such as heartburn, as a study endpoint. However, it has been shown that most nocturnal reflux events are silent, and do not cause classic symptoms of acid reflux or heartburn.
The purpose of this study is to determine if silent acid-induced sleep arousals have characteristics that differ from spontaneous sleep arousals on polysomnography.
Methods: The records of 16 patients who had previously undergone simultaneous polysomnography and overnight esophageal pH analysis, were reviewed. A sleep arousal was defined as a shift in EEG frequency lasting for at least 3 seconds, but no more that 15 seconds. An esophageal reflux event was considered to have occurred when the pH recording was < 4.0. Arousals were reflux associated if they occurred while the pH was below 4.0 and up to 5 minutes after the pH had returned to 4.0. For each acid associated arousal, a corresponding spontaneous arousal was chosen for comparison.
Results: There were a total of 33 overnight acid reflux events, which resulted in 27 acid induced arousals. Ten acid induced arousals occurred in stage 1 sleep, while 17 occurred in stage 2 sleep. No acid induced arousal occurred during stage 3, 4 or REM sleep. Of the 27 non-acid induced arousals analyzed, 5 occurred in stage 1 sleep, 18 occurred in stage 2 sleep, and 4 occurred in REM sleep. There were no arousals during stage 3 or 4 sleep. The mean duration of an acid induced arousal was 5.2 sec compared to 5.6 sec for spontaneous arousals (p > 0.05). Eleven acid induced arousals occurred while the patient was supine, and 16 occurred while the patient was on their right side. In comparison, eight non-acid induced arousals occurred while the patient was supine and 19 occurred while the patient was on their right side. No acid or non-acid induced arousals occurred while the patients where on their left side.
Conclusions: Silent acid induced arousals are indistinguishable from spontaneous non-acid induced arousals in duration and body position. Sleep disturbances with multiple sleep arousals may be due to silent acid reflux episodes, which are scored during polysomnography as being spontaneous arousals.
Thus, silent gastroesophageal reflux may present and be diagnosed as a primary sleep disorder.