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CPAP treatment reduces elevated muscle sympathetic nerve activity in patients with OSA

The use of continuous positive airway pressure treatment for 6 months reversed brain stem changes caused by elevated muscle sympathetic nerve activity in patients with obstructive sleep apnea, according to study results.

“Our results show that 6 months of CPAP treatment significantly reduces the elevated muscle sympathetic nerve activity [MSNA] and the associated brainstem functional and anatomical changes associated with obstructive sleep apnea [OSA],” Linda C. Lundblad, PhD, of University of Western Sydney School of Medicine in Australia, and colleagues wrote. “These data show that the underling mechanisms responsible for elevated MSNA in OSA are indeed reversible and highlight the effectiveness of CPAP treatment in reducing one of the most significant health issues associated with OSA.”

Lundblad and colleagues recorded MSNA and blood oxygen level-dependent (BOLD) brain stem signal intensity in 13 patients and 15 controls using high-resolution functional MRI. Prior to CPAP treatment, OSA patients had significantly elevated systolic (143 ± 5 mmHg) and diastolic (84 ± 2 mmHg) pressures compared with the control group (121 ± 4 mmHg systolic and 68 ± 4 mmHg diastolic).

OSA patients had a BMI of 30, and their BMI did not significantly change during the study period. Of the OSA patients studied, one patient had mild OSA, one had moderate OSA and 11 patients had severe OSA as defined by the number of apnea-hypopnea events per hour; control patients had an average of 3 ± 1 apnea-hypopnea events per hour compared to more than 30 events per hour in the most severe OSA group.

After 6 months of CPAP treatment, OSA patients had significantly reduced their MSNA from 54 ± 4 bursts per minute to 23 ± 3 bursts per minute. Burst incidence for these patients reduced from 77 ± 7 bursts per 100 heart beats to 36 ± 3 bursts per 100 heart beats. Lundblad and colleagues noted that CPAP treatment had a significant effect on diastolic, but not systolic blood pressure or heart rate.

“Signal intensity within the medullary raphe, rostral ventrolateral medulla and dorsolateral pons, which was significantly reduced in OSA subjects prior to CPAP treatment compared with controls, returned towards control levels following 6 months of CPAP treatment,” Lundblad and colleagues wrote. “Furthermore, grey matter increases that were observed in these brainstem regions in OSA subjects prior to CPAP treatment, reduced to control levels and even below following CPAP treatment. These data strongly suggest that functional and anatomical changes within the brainstem, which we believe underlies the elevated sympathetic activity in individuals with untreated OSA, can be restored to healthy levels by CPAP treatment.” – by Jeff Craven

Disclosure: The researchers report no relevant financial disclosures.