Aim Homozygous sickle cell anaemia (SCA; HbSS) is associated with neurological compromise and attention difficulties. Previous work has shown tentative links between executive dysfunction and daytime oxygen desaturation in SCA. Previous work has not however examined the effects of nocturnal oxygen saturation on attention, nor has it considered whether any relationship is confounded by the effects of socio-economic status (SES) or age.

Methods Thirteen children (8–12 years, 6 Female) and twentytwo adolescents (13–18 years, 11 Female) with SCA enrolled on the Prevention of Morbidity in Sickle Cell Disease Phase 2 randomised controlled trial of auto-adjusting continuous positive airways pressure underwent cognitive assessment at baseline, which included the Conners’ Continuous Performance Test (CPT). Overnight oximetry was conducted at home within two weeks of assessment. Multiple deprivation indices (MDI) were derived from postcodes.

Results In adolescents, after correcting for the effects of MDI, correlations were found between time spent with oxygen saturation <94% and Conners’ CPT detectability (r=0.430, p=0.036) and omissions (r=0.418, p=0.042), and between the time spent with oxygen saturation <84% and detectability (r=0.728, p=0.0001), omissions (r=0.566, p=0.004), commissions (r=0.679, p=0.0001), perseverations (r=0.898, p=0.0001), hit reaction time (r=0.372, p=0.0001), and variability (r=0.776, p=0.0001). Relationships were also found between mean nocturnal oxygen saturation and hit reaction time (RT; r= 0.374, p=0.072), omissions (r=0.360, p=0.084) and RT standard deviation (r= 0.389, p=0.060), between minimum nocturnal oxygen saturation and perseverations (r= 0.374, p=0.072) and between the number of 3% oxygen dips per hour and RT (r=0.354, p=0.089). In children the only relationship found was a trend in the opposite direction between RT and mean overnight oxygen saturation (r=0.502, p=0.067).

Conclusion This study confirms, for the first time in SCA, links between hypoxia and attention deficits. The relationships hold when SES is taken into account. The absence of similar links and existence of a relationship in the opposite direction in children requires further scrutiny. These preliminary data indicate that the effects of hypoxia on these domains may only emerge during brain development in adolescence. CPT performance may serve as a useful cognitive endpointfor trials of reducing hypoxic exposure.