LAUSR

For the first time, we comprehensively investigated the effects of repeated exposures to baseline (BL), total sleep deprivation (TSD), and recovery (REC) phases at 2, 4, and 8 months on cardiovascular (CV) measures. We conducted a five-day experiment twice (at months 2 and 4) in a 4-month study (N=6 healthy adults; 3 females), and a similar five-day experiment three times (at months 2, 4, and 8) in an 8-month study (N=5 healthy adults; 2 females). During these repeated experiments, CV measures were collected via echocardiography or blood pressure monitor [systolic and diastolic blood pressure (SBP and DBP)] at three assessment time points: 1) after two baseline 8h time in bed (TIB) nights (BL); 2) after a night of total sleep deprivation (TSD); and 3) after two recovery nights of 8-10h TIB (REC). CV measures were also collected once pre and post study. Seated stroke volume (SV), cardiac index (CI), left ventricular ejection time (LVET), SBP and DBP, systemic vascular resistance index (SVRI), and mean arterial pressure (MAP) were collected. Data did not significantly differ between the two studies and therefore were pooled together for analysis (N=11). Repeated measures ANOVA and post-hoc comparisons corrected for multiple testing examined CV measures across all time points. SV, CI, SVRI, LVET, and SBP, but not DBP or MAP, showed significant changes across time. SV increased with TSD compared to pre-study, BL, and post-study at month 2. CI increased with TSD compared to pre-study, BL, REC, and post-study at month 2. SVRI decreased with TSD compared to pre-study, BL, and REC at month 2 and LVET and SBP increased with TSD compared to BL at month 2. In the 8-month sample subset, SBP increased with TSD compared to BL at month 8. TSD increased SV, CI, LVET, and SBP, and decreased SVRI, compared to BL at month 2. Notably, TSD also increased SBP compared to BL at month 8, indicating a sustained adverse effect after long-duration repeated exposure to TSD. Overall, SV, CI, SVRI, LVET, and SBP are reliable biomarkers for assessing the harmful long-term cardiovascular effects of TSD. NASA grants NNX14AN49G and 80NSSC20K0243 (NG)