title: Association of serum phosphorus concentration with mortality in elderly and nonelderly hemodialysis patients.
abstract: OBJECTIVE
  Hypo- and hyperphosphatemia have each been associated with increased mortality in maintenance hemodialysis (MHD) patients. There has not been previous evaluation of a differential relationship between serum phosphorus level and death risk across varying age groups in MHD patients.
  
  
  METHODS
  In a 6-year cohort of 107,817 MHD patients treated in a large dialysis organization, we examined the association between serum phosphorus levels with all-cause and cardiovascular mortality within 5 age categories (15 to <45, 45 to <65, 65 to <70, 70 to <75, and ≥75 years old) using Cox proportional hazards models adjusted for case-mix covariates and malnutrition inflammation complex syndrome (MICS) surrogates.
  
  
  METHODS
  All-cause and cardiovascular mortality.
  
  
  RESULTS
  The overall mean age of the cohort was 60 ± 16 years, among whom there were 45% women, 35% Blacks, and 58% diabetics. The time-averaged serum phosphorus level (mean ± SD) within each age category was 6.26 ± 1.4, 5.65 ± 1.2, 5.26 ± 1.1, 5.11 ± 1.0, and 4.88 ± 1.0 mg/dL, respectively (P for trend <.001). Hyperphosphatemia (>5.5 mg/dL) was consistently associated with increased all-cause and cardiovascular mortality risks across all age categories, including after adjustment for case-mix and MICS-related covariates. In fully adjusted models, a low serum phosphorus level (<3.5 mg/dL) was associated with increased all-cause mortality only in elderly MHD patients ≥65 years old (hazard ratio [95% confidence interval]: 1.21 [1.07-1.37], 1.13 [1.02-1.25], and 1.28 [1.2-1.37] for patients 65 to <70, 70 to <75, and ≥75 years old, respectively), but not in younger patients (<65 years old). A similar differential cardiovascular mortality risk for low serum phosphorus levels between old and young age groups was observed.
  
  
  CONCLUSIONS
  The association between hyperphosphatemia and mortality is similar across all age groups of MHD patients, whereas hypophosphatemia is associated with increased mortality only in elderly MHD patients. Preventing very low serum phosphorus levels in elderly dialysis patients may be associated with better outcomes, which needs to be examined in future studies.
authors: Division of Nephrology and Hypertension, Harold Simmons Center for Chronic Disease Research & Epidemiology, University of Irvine Medical Center, Orange, California; Royal Irrigation Hospital, Srinakharinwirot University, Nonthaburi, Thailand.
authors: Paungpaga
authors: P
authors: Lertdumrongluk
authors: Connie M
authors: CM
authors: Rhee
authors: Jongha
authors: J
authors: Park
authors: Wei Ling
authors: WL
authors: Lau
authors: Hamid
authors: H
authors: Moradi
authors: Jennie
authors: J
authors: Jing
authors: Miklos Z
authors: MZ
authors: Molnar
authors: Steven M
authors: SM
authors: Brunelli
authors: Allen R
authors: AR
authors: Nissenson
authors: Csaba P
authors: CP
authors: Kovesdy
authors: Kamyar
authors: K
authors: Kalantar-Zadeh
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002318:Cardiovascular Diseases / Q000097:blood / Q000150:complications / Q000401:mortality; D015331:Cohort Studies; D005260:Female; D006801:Humans; D054559:Hyperphosphatemia / Q000097:blood* / Q000150:complications / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D010758:Phosphorus / Q000097:blood*; D006435:Renal Dialysis / Q000401:mortality*
chemical_list: D010758:Phosphorus
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