title: Disturbed mineral metabolism is associated with muscle and skin complaints in a prospective cohort of dialysis patients.
abstract: BACKGROUND
  Disturbed mineral metabolism is associated with increased morbidity and mortality, however, its influence on physical symptoms is less clear. We explored the effects of disordered plasma calcium, phosphorus, calcium-phosphorus (Ca x P) product and intact parathyroid hormone (iPTH) concentrations according to the K/DOQI guideline for bone metabolism and disease on the risk of muscle and skin complaints in dialysis patients.
  
  
  METHODS
  As part of NECOSAD, a prospective multicentre study in the Netherlands, we included 1469 consecutive patients who started haemodialysis or peritoneal dialysis between 1997 and 2004. Muscle pain, cramps and itching (pruritus) and dry (xerosis) skin were repeatedly measured using the Kidney Disease Quality of Life-Short Form questionnaire. Odds ratios (OR) for the risk of complaints over time were calculated by generalized estimating equations (GEE) models.
  
  
  RESULTS
  Mean age was 59 +/- 15 years, 61% of the patients were male and 63% were on haemodialysis. At baseline >65% of the patients had muscle and skin complaints. Compared with patients who met the target, the risk of muscle pain was increased in patients with hyperphosphataemia [OR: 1.2; 95% confidence interval (CI): 1.1-1.5] iPTH concentrations below the target range were associated with lower risk of cramps (OR 0.8, 95%CI: 0.6-0.9). The risk of pruritus was increased in patients with severely elevated plasma calcium (OR 1.4; 95%CI: 1.1-1.7), phosphorus (OR 1.4; 95%CI: 1.1-1.7) and Ca x P product levels (OR 1.6; 95%CI: 1.3-2.0). Finally, increased plasma calcium concentrations were associated with an elevated risk of xerosis (OR 1.4; 95%CI: 1.1-1.9).
  
  
  CONCLUSIONS
  Disturbed mineral metabolism according to the K/DOQI guideline is associated with more muscle and skin complaints in dialysis patients. These findings emphasize the importance of keeping mineral metabolism in dialysis patients in tight control.
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Centre, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands. m.noordzij@amc.uva.nl
authors.forename: Marlies
authors.initials: M
authors.lastname: Noordzij
authors.forename: Elisabeth W
authors.initials: EW
authors.lastname: Boeschoten
authors.forename: Willem J
authors.initials: WJ
authors.lastname: Bos
authors.forename: Friedo W
authors.initials: FW
authors.lastname: Dekker
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Bossuyt
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Krediet
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Korevaar
mesh_terms: D000368:Aged; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008903:Minerals / Q000378:metabolism; D009120:Muscle Cramp / Q000175:diagnosis* / Q000209:etiology; D009132:Muscles / Q000473:pathology*; D010281:Parathyroid Hormone / Q000097:blood*; D010758:Phosphorus / Q000097:blood*; D011446:Prospective Studies; D011537:Pruritus / Q000175:diagnosis* / Q000209:etiology; D006435:Renal Dialysis / Q000009:adverse effects* / Q000379:methods*; D012306:Risk; D012867:Skin / Q000473:pathology*; D013997:Time Factors
chemical_list: D008903:Minerals; D010281:Parathyroid Hormone; D010758:Phosphorus; D002118:Calcium