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Abstract During long-duration spaceflight, astronauts experience headward fluid shifts and expansion of the cerebral perivascular spaces (PVS). A major limitation to our understanding of the changes in brain structure and physiology induced by spaceflight stems from the logistical difficulties of studying astronauts. The current study aimed to determine whether PVS changes also occur on Earth with the spaceflight analog head-down tilt bed rest (HDBR). We examined how the number and morphology of magnetic resonance imaging-visible PVS (MV-PVS) are affected by HDBR with and without elevated carbon dioxide (CO2). These environments mimic the headward fluid shifts, body unloading, and elevated CO2 observed aboard the International Space Station. Additionally, we sought to understand how changes in MV-PVS are associated with signs of Spaceflight Associated Neuro-ocular Syndrome (SANS), ocular structural alterations that can occur with spaceflight. Participants were separated into two bed rest campaigns: HDBR (60 days) and HDBR + CO2 (30 days with elevated ambient CO2). Both groups completed multiple magnetic resonance image acquisitions before, during, and post-bed rest. We found that at the group level, neither spaceflight analog affected MV-PVS quantity or morphology. However, when taking into account SANS status, persons exhibiting signs of SANS showed little or no MV-PVS changes, whereas their No-SANS counterparts showed MV-PVS morphological changes during the HDBR + CO2 campaign. These findings highlight spaceflight analogs as models for inducing changes in MV-PVS and implicate MV-PVS dynamic compliance as a mechanism underlying SANS. These findings may lead to countermeasures to mitigate health risks associated with human spaceflight.

OBJECTIVES/GOALS: Weaimed to compare subjective and objective sleep in individuals with chronic post-concussive symptoms. We hypothesized an association between self-reported sleep quality and objective sleep parameters, which is different for concussed and control cohorts. METHODS/STUDY POPULATION: 28 individuals with chronic post-concussive symptoms and 13 age-matched controls (no concussion history) completed the ISI, PSQI, PROMIS Depression, Anxiety, Stress and Cognitive questionnaires at enrollment. Objective sleep parameters were obtained for a minimum of 7 days and up to 30 days with a validated sleep monitoring device placed under the subject’s bed (Emfit). For each night, raw activity data per minute were analyzed to determinein-bed, sleep, wake, andout-of-bedtimes. These measures were used to calculate total sleep time (TST), sleep onset latency (SOL), and wake after sleep onset (WASO) for each night. RESULTS/ANTICIPATED RESULTS: Concussed individuals reported worse sleep with PSQI and ISI scores significantly higher than controls. They also showedsignificant associations between PSQI and Dep ression, ISI and Depression, and ISI and Anxiety scores. There was no difference between objective sleep parameters in the concussed and control cohorts (in-bed/sleep/wake/out-of-bed times, TST, SOL, and WASO). Instead, higher PSQI, ISI, Depression, Anxiety, and Stress scores (greater symptom burden) were all associated with later sleep times, where as higher Cognitive scores (greater cognitive function) were associated with earlier sleep times, regardless of group status. DISCUSSION/SIGNIFICANCE: Concussed individuals report worse subjective sleep but no differences to controls when objectively assessing sleep. Depression/anxiety, and not concussion status, determine objective sleep parameters. Psychiatric comorbidities should inform the treatment of post-concussive sleep disturbances.