Untreated Moderate-to-Severe Sleep-Related Breathing Disorders Are Associated with Increased Frequency of Episodes of Autonomic Dysreflexia during Sleep in Individuals with Subacute or Chronic Spinal Cord Injury: A Prospective Cross-Sectional Study.
Julio Furlan1, Eldon Loh2, Mark Boulos3
1Lyndhurst Centre, KITE Research Institute, University Health Network; University of Toronto, 2Western University, 3Sunnybrook Health Sciences, University of Toronto Centre
Objective:
This ongoing cross-sectional study is focused on the potential association between moderate-to-severe sleep-related breathing disorders (SRBDs) and more severe cardiovascular dysfunction following spinal cord injury (SCI).
Background:
Sleep-related breathing disorders (SRBDs) are common and under-recognized among individuals living with spinal cord injury (SCI). SRBDs can affect the sympathetic response, but the impact of untreated SRBDs on cardiovascular autonomic function after SCI remains incompletely understood.
Design/Methods:
This cross-sectional study included adults with subacute/chronic (≥1 month after SCI onset), cervical or high-thoracic (T6 or above) SCI. The diagnosis of SRBD was established using a home-based/hospital unattended sleep screening test that quantifies the apnea-hypopnea index (AHI). Moderate-to-severe SRBD was defined as an AHI ≥ 15 events per hour. Episodes of autonomic dysreflexia (AD) were defined as a sudden increase in systolic blood pressure (BP) ≥ 20 mmHg.
Results:
This study included 45 individuals (14 females, 31 males with ages from 20 to 84 years; mean age: 57.0 years) with motor complete (n=22) or incomplete (n=24) SCI at cervical (n=38), or high thoracic levels. Time from SCI onset varied from 1.5 months to 52 years (mean time: 49.4 months). Mean AHI was 16.0 events per hour (AHI range: 0.8-51.7). The AHI was not associated with systolic BP (mean+/-SEM: 122.0+/-2.2 mmHg; p=0.903), diastolic BP (72.6+/-3.0 mmHg; p=0.639), mean arterial pressure (90.1+/-2.4 mmHg; p=0.714), and heart rate (70.6+/-1.4 bpm; p=0.669) during sleep. However, the AHI was significantly, positively correlated with the number of silent episodes of AD (mean +/- SEM: 3.6+/-0.4; Rsqr=0.220, p=0.001) during sleep, after excluding other causes of AD.
Conclusions:
The results of this cross-sectional study suggest that more severe SBRBs are associated with frequent silent episodes of AD during sleep among individuals with SCI. Future research is needed to assess the effects of continuous positive airway pressure (CPAP) therapy on cardiovascular dysfunction following SCI.