Cortisol, sleep and cognition in sickle cell anaemia

Objectives/Introduction: Cortisol is critical for supporting a healthy immune system, maintaining energy levels and cognitive function- ing. The relationship of cortisol, cognition and sleep in sickle cell dis- ease (SCD) is not well understood. Methods: Participants of African heritage (Meanage = 19.37, Nmale= 16, Ncontrol = 18, NSCD= 27) were recruited from the community in London, UK. Salivary cortisol was taken 4 times on a week day. Sleep was measured with an Actiwatch (CamNtech) for 7 nights. Assessment from the Wechsler Scales of Intelligence occurred within 7 days of data collection. Results: Both groups slept on average 6 h, but SCD experienced greater sleep fragmentation (SF) and night wake bouts (WB) (SF; 31% & WB; 41) compared to controls (SF; 25% & WB; 34, both p < 0.05). SCD had numerically greater sleep latency of 48 min (range:8min-3h6min)comparedto35min(range:3min-1h 55 min) for controls (p = 0.21). The mean full-scale IQ, processing speed index (PSI) and perceptual reasoning index (PRI) were lower in SCD: FSIQSCD = 95 (SD = 11.8) & FSIQcontrols= 107.22 (SD = 9.55), PSISCD = 90.56 (SD = 13.3) & PSIcontrols= 106.78 (SD = 10.38, both p < 0.01) & PRISCD = 101.11 (SD = 13.95) & PRIcontrols= 108.24 (SD = 10.69), p = 0.06. SCD showed a flatter cortisol profile with lower normalized cortisol in the afternoon (54%) compared to controls (89%, p = 0.027). There was a positive correlation be- tween morning cortisol and PRI (r (45) = 0.41, p < 0.01) and PSI (r (45) = 0.30, p < 0.05), suggesting that greater increase in morning cortisol might be beneficial for cognitive performance. Hierarchical multiple regression revealed that WB and morning cortisol predict PSI(R2 =0.575,F(3,41)=6.76,p=0.001)andPRI(R2 =0.514,F(3, 41) = 4.9, p = 0.005) in patient and controls. Conclusions: Morning cortisol and WB could be contributing fac- tors to the observed cognitive differences in SCD. Frequent WB and SF might be an indicator of sleep disordered breathing in SCD. It is important to understand what drives the relationship between sleep and cognitive difficulties to develop interventions early on for chil- dren with SCD