P024 The Obstructive Sleep Apnoea Endotypes are Similar in Elderly Veterans with and without PTSD.

BACKGROUND: Approximately 60% of veterans living with post-traumatic stress disorder (PTSD) experience obstructive sleep apnoea (OSA). Why OSA is so prevalent in individuals with PTSD remains unknown, though the presence of PTSD may influence the underlying endotypes known to cause OSA. We examined whether upper airway collapsibility, muscle compensation, loop gain, and the arousal threshold differ in trauma exposed elderly male veterans with OSA with and without comorbid PTSD. METHODS: Using the ventilatory flow pattern from diagnostic polysomnography, the four OSA endotypes were measured in a retrospective cohort of 21 OSA patients with PTSD and 27 OSA-only patients. All participants are male Vietnam War veterans with mild-to-severe OSA (AHI M=26.8, SD=18.6; range: 6.0-105.9 events/h). Age (M=71.3, SD=3.5) and BMI (M=27.4, SD=3.4 kg/m²) were similar between groups. RESULTS: There were no statistically significant differences (p-values>0.3) in the OSA endotype traits between OSA-only and OSA+PTSD patients for upper airway collapsibility (78.35 [72.81-83.82] vs. 76.68 [71.53-83.56]%eupnea), muscle compensation (5.41 [1.83-7.21] vs. 4.27 [0.34-9.18]%eupnea), arousal threshold (146.95 [128.64-151.28] vs. 135.76 [126.59-147.54]%eupnea), and loop gain (M=0.60, SD=0.14 vs. M=0.56, SD=0.17). CONCLUSION: The endotypes underlying OSA in elderly male veterans with PTSD were similar to their trauma exposed OSA-only counterparts. PTSD may exert little influence on the OSA endotypes in elderly samples beyond the effect that age and trauma exposure may have in OSA patients. What underlies the increased prevalence of OSA in PTSD remains unclear and further work examining these endotypes using larger and more diverse samples is needed before robust conclusions can be made.