title: Nocturnal haemoglobin oxygen saturation variability is associated with vitamin C deficiency in Tanzanian children with sickle cell anaemia.
abstract: OBJECTIVE
  To compare pulse oximetry in children with sickle cell anaemia (SCA) and controls and test the hypothesis that vitamin C deficiency (VCD; <11.4 μmol/L) is associated with nocturnal haemoglobin oxygen desaturation in SCA.
  
  
  METHODS
  We undertook nocturnal and daytime pulse oximetry in 23 children with SCA (median age 8 years) with known steady-state plasma vitamin C concentrations and 18 siblings (median 7 years).
  
  
  RESULTS
  Median nocturnal delta 12 s index (delta12 s), a measure of haemoglobin oxygen saturation (SpO(2)) variability, was 0.38 (interquartile range 0.28-0.51) in SCA and 0.35 (0.23-0.48) in controls, with 9/23 and 6/18, respectively, having a delta12 s >0.4, compatible with obstructive sleep apnoea (OSA). Eleven of twenty-three with SCA had VCD; logged vitamin C concentrations showed a 66% decrease per 0.1 unit increase in delta12 s ([95% CI -86%, -15%]; p=0.023) and delta12 s >0.4 was associated with VCD (odds ratio 8.75 [1.24-61.7], p=0.029). Daytime and mean nocturnal SpO(2) were lower in SCA but there was no association with vitamin C.
  
  
  CONCLUSIONS
  Obstructive sleep apnoea (OSA), detected from nocturnal haemoglobin oxygen saturation variability, is common in Tanzanian children and associated with vitamin C Deficiency in SCA. The direction of causality could be determined by comparing OSA treatment with vitamin C supplementation.
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK. sharon.cox@lshtm.ac.uk
authors.forename: S E
authors.initials: SE
authors.lastname: Cox
authors.forename: V
authors.initials: V
authors.lastname: L'Esperance
authors.forename: J
authors.initials: J
authors.lastname: Makani
authors.forename: D
authors.initials: D
authors.lastname: Soka
authors.forename: C M
authors.initials: CM
authors.lastname: Hill
authors.forename: F J
authors.initials: FJ
authors.lastname: Kirkham
mesh_terms: D000293:Adolescent; D000755:Anemia, Sickle Cell / Q000097:blood* / Q000503:physiopathology; D001206:Ascorbic Acid Deficiency / Q000097:blood* / Q000150:complications; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000150:complications; D013636:Tanzania
chemical_list: D006454:Hemoglobins; D010100:Oxygen