title: Impact of age on survival predictability of bone turnover markers in hemodialysis patients.
abstract: BACKGROUND
  Abnormalities in serum alkaline phosphatase (ALP) and intact parathyroid hormone (PTH) concentrations, as biochemical markers of bone turnover in dialysis patients, correlate with increased mortality in maintenance hemodialysis (MHD) patients. Changes in bone turnover rate vary with age. The mortality predictability of serum ALP and PTH levels in MHD patients may be different across ages.
  
  
  METHODS
  We examined differences across four age groups (18 to <45, 45 to <65, 65 to <75 and ≥ 75 years) in the mortality predictability of serum ALP and PTH in 102 149 MHD patients using Cox models.
  
  
  RESULTS
  Higher serum ALP levels were associated with higher mortality across all ages; however, the ALP-mortality association was much stronger in young patients (<45 years) compared with older patients. The association between higher serum PTH levels and mortality was stronger in older patients compared with the younger groups. Serum PTH levels were incrementally associated with mortality only in middle-aged and elderly patients (≥ 45 years). Compared with patients with serum PTH 150 to <300 pg/mL, the death risks were higher in patients with serum PTH 300 to <600 pg/mL [HRs (95% CI): 1.05 (1.01-1.10), 1.15 (1.10-1.21) and 1.25 (1.19-1.31) for patients 45 to <65, 65 to <75 and ≥ 75 years, respectively], and ≥ 600 pg/mL [HRs(95% CI): 1.07 (1.01-1.14), 1.31(1.21-1.42) and 1.45(1.33-1.59) for age categories 45 to <65, 65 to <75 and ≥ 75 years, respectively]. However, no significant association between higher serum PTH levels and mortality was observed in patients <45 years.
  
  
  CONCLUSIONS
  There are important differences in mortality-predictability of serum ALP and PTH in older MHD patients compared with their younger counterparts. The effect of age needs to be considered when interpreting the prognostic implications of serum ALP and PTH levels.
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, Division of Nephrology & Hypertension, Orange, CA, USA.
authors.forename: Paungpaga
authors.initials: P
authors.lastname: Lertdumrongluk
authors.forename: Wei Ling
authors.initials: WL
authors.lastname: Lau
authors.forename: Jongha
authors.initials: J
authors.lastname: Park
authors.forename: Connie M
authors.initials: CM
authors.lastname: Rhee
authors.forename: Csaba P
authors.initials: CP
authors.lastname: Kovesdy
authors.forename: Kamyar
authors.initials: K
authors.lastname: Kalantar-Zadeh
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000097:blood*; D016723:Bone Remodeling; D001842:Bone and Bones / Q000378:metabolism*; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000378:metabolism / Q000401:mortality*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D011379:Prognosis; D006435:Renal Dialysis / Q000401:mortality*; D015996:Survival Rate; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D000469:Alkaline Phosphatase
keywords: age; alkaline phosphatase; bone turnover markers; hemodialysis; parathyroid hormone
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