Gastroesophageal reflux disease (GERD) is very common. The more loosely defined, the more common it is. In a telephone survey accessing >20,000 randomly selected US residents, 22% report having heartburn at least once a month.1 Even using a more restrictive definition, GERD is common. A population-based endoscopy study of 1,000 Scandinavians found a 15.5% prevalence of esophagitis.2 Herein lies the problem in examining the relationship between GERD and obstructive sleep apnea (OSA). Are we simply looking at two common conditions that may well coexist in an individual? Do they commonly coexist because of shared risk factors? Or does a causal relationship exist between them?