title: A propensity-matched study of low serum potassium and mortality in older adults with chronic heart failure.
abstract: OBJECTIVE
  Most HF patients are older adults, yet the associations of low serum potassium and outcomes in these patients are unknown. We studied the effect of low serum potassium in a propensity-matched population of elderly HF patients.
  
  
  METHODS
  Of the 7788 patients in the Digitalis Investigation Group trial, 4036 were >or=65 years. Of these, 3598 had data on baseline serum potassium and 324 with potassium >or=5 mEq/L were excluded. Remaining patients were categorized into low (<4 mEq/L; n=590) and normal (4-4.9 mEq/L; n=2684) potassium groups. Propensity scores for low-potassium, calculated for each patient, were used to match 561 low-potassium and 1670 normal-potassium patients. Association of low potassium and outcomes were assessed using matched Cox regression analyses.
  
  
  RESULTS
  Patients had a mean (+/-SD) age of 72 (+/-6) years, 29% were women and 12% were non-whites. Of the 561 low-potassium patients, 500 had low-normal (3.5-3.9 mEq/L) potassium. All-cause mortality occurred in 37% (rate, 1338/10,000 person-years) normal-potassium and 43% (rate, 1594/10,000 person-years) low-potassium patients (hazard ratio {HR} for low-potassium, 1.22; 95% confidence interval {CI}, 1.04-1.44; p=0.014). Low-normal (3.5-3.9 mEq/L) potassium levels had a similar association with mortality (HR, 1.19, 95% CI, 1.00-1.41, p=0.049). Low (HR, 1.10; 95% CI, 0.96-1.25; p=0.175) or low-normal (HR=1.09, 95% CI=0.95-1.25, p=0.229) serum potassium levels were not associated with all-cause hospitalization.
  
  
  CONCLUSIONS
  In a propensity-matched population of elderly ambulatory chronic HF patients, well-balanced in all measured baseline covariates, low and low-normal serum potassium were associated with increased mortality but had no association with hospitalization.
authors.affiliation: Tulane University, New Orleans, Louisiana, USA.
authors.forename: A Brent
authors.initials: AB
authors.lastname: Alper
authors.forename: Ruth C
authors.initials: RC
authors.lastname: Campbell
authors.forename: Stefan D
authors.initials: SD
authors.lastname: Anker
authors.forename: George
authors.initials: G
authors.lastname: Bakris
authors.forename: Christy
authors.initials: C
authors.lastname: Wahle
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Love
authors.forename: L Lee
authors.initials: LL
authors.lastname: Hamm
authors.forename: Marjan
authors.initials: M
authors.lastname: Mujib
authors.forename: Ali
authors.initials: A
authors.lastname: Ahmed
mesh_terms: D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002908:Chronic Disease; D005260:Female; D006333:Heart Failure / Q000097:blood* / Q000401:mortality*; D006760:Hospitalization / Q000639:trends; D006801:Humans; D008297:Male; D011188:Potassium / Q000097:blood*
chemical_list: D015415:Biomarkers; D011188:Potassium