Although low Spo2 predicts neurologic complications in SCA,48 in patients with hemoglobinopathies, right shift of the oxygen dissociation curve and the presence of carboxyhemoglobin and methemoglobin may lead to overestimation.49 Daytime and nocturnal Spo2 are not necessarily correlated in SCA, with a greater proportion of patients experiencing desaturation at night.50 Furthermore, we used postcode rather than direct measures of SES, which were unavailable for the majority. This evidence concerns the gene HBG2 and hemoglobinopathy.