0625 Characterization of Obstructive Sleep Apnea in Active-Duty US Military Personnel Receiving Interdisciplinary Care at the National Intrepid Center of Excellence

Introduction

Among active-duty service members (ADSMs), obstructive sleep apnea (OSA) is associated with decreased quality of life and military readiness/retention. Limited evidence suggests mild traumatic brain injury (mTBI) patients have increased OSA incidence, but little is known about the underlying physiology. This study aims to characterize OSA in treatment-seeking ADSMs with a history of remote mTBI and/or persistent neurobehavioral symptoms to improve detection and early intervention.

Methods

This is a retrospective analysis of data collected from ADSMs attending the National Intrepid Center of Excellence Intensive Outpatient Program for persistent symptoms associated with mTBI. Sleep assessment included overnight polysomnography and self-report assessments of sleep quality, somatic and mood symptoms. OSA severity was determined by apnea-hypopnea index (negative: <5, mild: 5-15, moderate/severe: ≥15). Group differences were assessed using analysis of covariance and pairwise least squares regression, controlling for age and body mass index, and corrected for multiple comparisons.

Results

Analyses included 574 ADSMs, mostly male (99%), with a mean age of 39.7. The majority (n=288; 50.2%) were OSA negative (OSA-neg); a third had mild OSA (m-OSA) (n=216; 38%); and a tenth were diagnosed with moderate/severe OSA (mod/s-OSA) (n=70; 12%). Mod/s-OSA patients had increased arousal index (p<0.01), hypoxia time (p<0.001), reduced total sleep time (p<0.01) and sleep efficiency (p<0.001) compared to m-OSA and OSA-neg patients. M-OSA patients had an increased arousal index compared to OSA-neg patients (p<0.01). Patient groups did not significantly differ on subjective measures of sleep (i.e., quality, sleepiness), post-concussive, or behavioral health symptoms (anxiety, depression, post-traumatic stress symptoms, alcohol misuse).

Conclusion

In our sample of treatment-seeking ADSMs, nearly half presented with OSA according to cut-scores derived for AHI, greater than that expected in the general population. As reported in civilian populations, mod/s-OSA patients demonstrated worse objective sleep measures compared to m-OSA and OSA-neg patients, yet in our sample their self-reported symptom severity did not differ. These findings suggest a low threshold for OSA screening is needed in the symptomatic mTBI population and that multiple factors other than OSA likely contribute to perceived sleep disturbances and neurobehavioral symptoms.

Support (If Any)

None.

RNA Toxicity and Perturbation of rRNA Processing in Spinocerebellar Ataxia Type 2

BACKGROUND

Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disease caused by expansion of a CAG repeat in Ataxin-2 (ATXN2) gene. The mutant ATXN2 protein with a polyglutamine tract is known to be toxic and contributes to the SCA2 pathogenesis.

OBJECTIVE

Here, we tested the hypothesis that the mutant ATXN2 transcript with an expanded CAG repeat (expATXN2) is also toxic and contributes to SCA2 pathogenesis.

METHODS

The toxic effect of expATXN2 transcripts on SK-N-MC neuroblastoma cells and primary mouse cortical neurons was evaluated by caspase 3/7 activity and nuclear condensation assay, respectively. RNA immunoprecipitation assay was performed to identify RNA binding proteins (RBPs) that bind to expATXN2 RNA. Quantitative PCR was used to examine if ribosomal RNA (rRNA) processing is disrupted in SCA2 and Huntington's disease (HD) human brain tissue.

RESULTS

expATXN2 RNA induces neuronal cell death, and aberrantly interacts with RBPs involved in RNA metabolism. One of the RBPs, transducin β-like protein 3 (TBL3), involved in rRNA processing, binds to both expATXN2 and expanded huntingtin (expHTT) RNA in vitro. rRNA processing is disrupted in both SCA2 and HD human brain tissue.

CONCLUSION

These findings provide the first evidence of a contributory role of expATXN2 transcripts in SCA2 pathogenesis, and further support the role of expHTT transcripts in HD pathogenesis. The disruption of rRNA processing, mediated by aberrant interaction of RBPs with expATXN2 and expHTT transcripts, suggest a point of convergence in the pathogeneses of repeat expansion diseases with potential therapeutic implications. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.