BACKGROUND: Sleep-related breathing disorders (SRBDs) affect as many as 40% of elderly people. The association of SRBDs with structural brain abnormalities remains unclear. In this observational study, we evaluated gray matter changes in the brain associated with sleep abnormalities in volunteers and their relationship with the severity of SRBDs. METHODS: One hundred fifty two healthy subjects aged 66.0 +/- 0.6 years-old underwent tridimensional brain MRI and nocturnal polygraphic recording during which apnea/hypopnea index (AHI) and the oxyhemoglobin desaturation index (ODI) were measured. Using voxel-based morphometry, we investigated the presence of gray matter abnormalities in association with AHI and ODI. FINDINGS: Seventy-six subjects (50%) had SRBDs defined by an AHI > or = to 15 and 25 subjects (16%) SRBDs defined by an ODI > or = 15, in the absence of systematic excessive daytime sleepiness. A significant symmetrical loss of gray matter in the intermediate reticular zone of the bulbopontine area was found to correlate with both AHI and ODI (P < 0.05 corrected for multiple comparisons for cluster significance). INTERPRETATION: This gray matter volume decrease in brain regions involved in breathing/autonomic functions, as well as their correlation with the severity of the disorder, suggests a pathophysiological link between structural changes and SRBDs.