Associations between severity and duration of sleep-disordered breathing and brain tissue volume

Abstract

Introduction: Cross-sectional studies indicate sleep-disordered breathing (SDB) is associated with structural brain alterations; it is unclear whether SDB precedes structural changes.

Aim: We investigated differences in brain tissue volume by prior SDB exposure in a population-based cohort. We hypothesized greater severity and longer duration of SDB is associated with lower tissue volume.

Methods: A subset of Wisconsin Sleep Cohort Study subjects (n=145; 51% female; mean[range] age=68[50-85] y) participated in a neuroimaging protocol. Up to 25 y of polysomnography data were used to characterize SDB history as never (apnea-hypopnea index [AHI]<5 on all studies), recent-onset (AHI≥5 for <10 y), or chronic (AHI≥5 for >10 y). Gray and white matter volume, total volume of white matter hyperintensities (WMH), and the ratio of WMH volume/total intracranial volume (ICV) were compared between SDB groups using linear regression. We also examined associations between most recent AHI and tissue volume variables.

Results: Total gray matter volume was lower among individuals with chronic SDB (beta=-19 mL, p<0.2) and new-onset SDB (beta=-18 mL, p<0.2) than those who never had SDB. Total white matter volume did not differ between SDB groups. Higher log(AHI+1) was associated with lower gray matter volume (beta=-36 mL per 10-fold increase in AHI, p<0.01), higher WMH volume (beta=7 mL per 10-fold increase in AHI, p<0.2), and a higher WMH/ICV ratio (beta=0.006 per 10-fold increase in AHI, p<0.05).

Conclusion: More prolonged and severe SDB is associated with lower brain volume. The difference in gray matter volume between chronic and no SDB groups was equivalent to what we found associated with 9 y of aging.