title: Serum phosphorus and mortality in the Third National Health and Nutrition Examination Survey (NHANES III): effect modification by fasting.
abstract: BACKGROUND
  Serum phosphorus levels have been associated with mortality in some but not all studies. Because dietary intake prior to measurement can affect serum phosphorus levels, we hypothesized that the association between serum phosphorus level and mortality is strongest in those who have fasted longer.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Nationally representative sample of 12,984 participants 20 years or older in the Third National Health and Nutrition Examination Survey (1988-1994).
  
  
  METHODS
  Serum phosphorus level, fasting duration (dichotomized as ≥ 12 or < 12 hours).
  
  
  RESULTS
  All-cause and cardiovascular mortality determined by death certificate data from the National Death Index.
  
  
  METHODS
  Serum phosphorus measured in a central laboratory and fasting duration recorded as time since food or drink other than water was consumed.
  
  
  RESULTS
  Individuals fasting 12 or more hours had lower serum phosphorus levels than those fasting less than 12 hours (3.34 vs 3.55 mg/dL; P < 0.001) and higher correlation with repeat measurement (0.66 vs 0.53; P = 0.002). In multivariable-adjusted Cox regression models, the highest quartile of serum phosphorus was associated with increased mortality in participants fasting 12 or more hours (adjusted HR, 1.74; 95% CI, 1.38-2.20; reference, lowest quartile) but not in participants fasting less than 12 hours (adjusted HR, 1.08; 95% CI, 0.89-1.32; P for interaction = 0.002). Relationships were consistent using 8 hours as the fasting cutoff point or cardiovascular mortality as the outcome.
  
  
  CONCLUSIONS
  Observational study, lack of fibroblast growth factor 23 or intact parathyroid hormone measurements.
  
  
  CONCLUSIONS
  Fasting but not nonfasting serum phosphorus levels were associated with increased mortality. Risk prognostication based on serum phosphorus may be improved using fasting levels.
authors.affiliation: Division of Nephrology, Geisinger Health System, Danville, PA. Electronic address: achang@geisinger.edu.
authors.forename: Alex R
authors.initials: AR
authors.lastname: Chang
authors.affiliation: Division of Nephrology, Johns Hopkins University, Baltimore, MD; Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, MD.
authors.forename: Morgan E
authors.initials: ME
authors.lastname: Grams
mesh_terms: D000328:Adult; D002318:Cardiovascular Diseases / Q000097:blood / Q000401:mortality; D002423:Cause of Death; D015331:Cohort Studies; D015987:Effect Modifier, Epidemiologic; D005215:Fasting / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D010758:Phosphorus / Q000097:blood*; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors; D013223:Statistics as Topic; D013997:Time Factors; D014481:United States / Q000453:epidemiology
chemical_list: D010758:Phosphorus
keywords: Phosphorus; cardiovascular; death; fast; fasting; mortality; phosphate