Does sleeping on a waterbed promote gastroesophageal reflux?

We conducted a randomized prospective study with extended intraesophageal pH monitoring on two consecutive nights to test the hypothesis that a waterbed (WB) might increase recumbent acid exposure compared to a regular bed (RB). We studied 10 controls (mean age 29 years; five males, five females) with no history of reflux symptoms more than two times per month. We also studied 10 reflux patients (mean age 42 years; seven males, three females) with symptoms at least five days a week and documented recumbent reflux, with or without upright reflux, by previous 24 hr pH study. A standard meal (56% fat) was provided at 6 PM. After randomization, the subjects and patients slept on the assigned bed (WB or RB) in one nearby hotel. The pH probe was removed the next morning at 8 AM. On the same day, the pH probe was inserted at 4 PM and the routine was repeated with use of the other bed. No significant difference (P greater than 0.05; paired t test) was found between the regular bed and waterbed in any measurement of recumbent reflux. Our study does not support the hypothesis that greater recumbent reflux may occur when sleeping flat on a waterbed compared to a regular bed. It does not, however, absolutely refute the possible association of waterbed use with esophagitis, since elevation of the head of a waterbed is not possible.