title: Case-control study of factors associated with nutritional rickets in Nigerian children.
abstract: OBJECTIVE
  Because the causes of nutritional rickets in tropical countries are poorly understood, we conducted a case-control study to determine factors associated with rickets in Nigerian children.
  
  
  METHODS
  We compared 123 Nigerian children who had rickets with matched control subjects. Dietary, demographic, anthropometric, and biochemical data were collected to assess factors related to calcium and vitamin D status, which might predispose children to rickets.
  
  
  RESULTS
  Mean (+/- SD) daily dietary calcium intake was low in both children with rickets and control children (217 +/- 88 mg and 214 +/- 77 mg, respectively; P =.64). Children with rickets had a greater proportion of first-degree relatives with a history of rickets (14.6% vs 3.1%; P <.001), a shorter mean duration of breast-feeding (16.0 vs 17.3 months; P =.041), and a delayed age of walking (14 vs 12 months; P <.001). Among children with rickets, biochemical features suggestive of calcium deficiency included hypocalcemia, extremely low calcium excretion, and elevated 1, 25-dihydroxyvitamin D and parathyroid hormone values. Median 25-hydroxyvitamin D concentrations were 32 and 50 nmol/L (13 and 20 ng/mL) in children with rickets and control children, respectively (P <.0001). Only 46 subjects with rickets (37%) had 25-hydroxyvitamin D values <30 nmol/L (12 ng/mL).
  
  
  CONCLUSIONS
  Vitamin D deficiency appears unlikely to be the primary etiologic factor of rickets in African children. Moreover, low dietary calcium intake alone does not account for rickets. Insufficient dietary calcium probably interacts with genetic, hormonal, and other nutritional factors to cause rickets in susceptible children.
authors.affiliation: Department of Family Medicine, Jos University Teaching Hospital, Jos, Nigeria.
authors.forename: T D
authors.initials: TD
authors.lastname: Thacher
authors.forename: P R
authors.initials: PR
authors.lastname: Fischer
authors.forename: J M
authors.initials: JM
authors.lastname: Pettifor
authors.forename: J O
authors.initials: JO
authors.lastname: Lawson
authors.forename: C O
authors.initials: CO
authors.lastname: Isichei
authors.forename: G M
authors.initials: GM
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000886:Anthropometry; D002118:Calcium / Q000172:deficiency / Q000652:urine; D002136:Calcium, Dietary / Q000008:administration & dosage; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D006996:Hypocalcemia / Q000150:complications; D008297:Male; D009549:Nigeria; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000008:administration & dosage; D012279:Rickets / Q000209:etiology* / Q000378:metabolism; D018709:Statistics, Nonparametric; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D014807:Vitamin D; D010758:Phosphorus; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium