Global Brain Blood-Oxygen Level Responses to Autonomic Challenges in Obstructive Sleep Apnea

• Published in: PloS one Vol. 9; no. 8; p. e105261
• Main Authors: Macey, Paul M., Kumar, Rajesh, Ogren, Jennifer A., Woo, Mary A., Harper, Ronald M.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 28.08.2014; Public Library of Science (PLoS)
• Subjects: Adult; Age; Apnea; Autonomic Nervous System - metabolism; Autonomic Nervous System - physiopathology; Biology and Life Sciences; Blood; Blood flow; Blood pressure; Blood Pressure - physiology; Blood volume; Brain; Brain - metabolism; Brain - physiopathology; Brain injury; Brain research; Cerebral blood flow; Cerebrovascular Circulation - physiology; Circulatory system; Cold pressing; Female; Females; Functional magnetic resonance imaging; Head injuries; Heart Rate - physiology; Humans; Hypoxia; Magnetic resonance; Magnetic Resonance Imaging; Male; Males; Medicine and Health Sciences; Middle Aged; Neuroimaging; NMR; Nuclear magnetic resonance; Oxygen; Oxygen - blood; Oxygenation; Perfusion; Research and Analysis Methods; Sex Factors; Sexually transmitted diseases; Sleep; Sleep apnea; Sleep Apnea, Obstructive - metabolism; Sleep Apnea, Obstructive - physiopathology; Sleep disorders; Standard error; STD; Variance analysis; Los Angeles California; United States > US; California
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0105261

Obstructive sleep apnea (OSA) is accompanied by brain injury, perhaps resulting from apnea-related hypoxia or periods of impaired cerebral perfusion. Perfusion changes can be determined indirectly by evaluation of cerebral blood volume and oxygenation alterations, which can be measured rapidly and non-invasively with the global blood oxygen level dependent (BOLD) signal, a magnetic resonance imaging procedure. We assessed acute BOLD responses in OSA subjects to pressor challenges that elicit cerebral blood flow changes, using a two-group comparative design with healthy subjects as a reference. We separately assessed female and male patterns, since OSA characteristics and brain injury differ between sexes. We studied 94 subjects, 37 with newly-diagnosed, untreated OSA (6 female (age mean ± std: 52.1±8.1 yrs; apnea/hypopnea index [AHI]: 27.7±15.6 events/hr and 31 male 54.3±8.4 yrs; AHI: 37.4±19.6 events/hr), and 20 female (age 50.5±8.1 yrs) and 37 male (age 45.6±9.2 yrs) healthy control subjects. We measured brain BOLD responses every 2 s while subjects underwent cold pressor, hand grip, and Valsalva maneuver challenges. The global BOLD signal rapidly changed after the first 2 s of each challenge, and differed in magnitude between groups to two challenges (cold pressor, hand grip), but not to the Valsalva maneuver (repeated measures ANOVA, p<0.05). OSA females showed greater differences from males in response magnitude and pattern, relative to healthy counterparts. Cold pressor BOLD signal increases (mean ± adjusted standard error) at the 8 s peak were: OSA 0.14±0.08% vs. Control 0.31±0.06%, and hand grip at 6 s were: OSA 0.08±0.03% vs. Control at 0.30±0.02%. These findings, indicative of reduced cerebral blood flow changes to autonomic challenges in OSA, complement earlier reports of altered resting blood flow and reduced cerebral artery responsiveness. Females are more affected than males, an outcome which may contribute to the sex-specific brain injury in the syndrome.