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A propensity-matched study of low serum potassium and mortality in older adults with chronic heart failure
A Brent Alper1, Ruth C Campbell, Stefan D Anker
1Tulane University, New Orleans, Louisiana, USA.
Insights
Low serum potassium in elderly heart failure (HF) patients is linked to increased mortality. This study found low or low-normal potassium levels were associated with higher death rates but not hospitalizations in older HF patients.
Area of Science:
- Cardiology
- Geriatrics
- Clinical Research
Background:
- Most heart failure (HF) patients are elderly.
- The impact of low serum potassium on outcomes in elderly HF patients remains understudied.
Purpose of the Study:
- To investigate the association between low serum potassium and clinical outcomes in elderly patients with chronic heart failure.
Main Methods:
- A propensity-matched analysis was conducted on elderly patients (>or=65 years) from the Digitalis Investigation Group trial.
- Patients were categorized into low (<4 mEq/L) and normal (4-4.9 mEq/L) serum potassium groups.
- Cox regression analyses assessed the association of low potassium with mortality and hospitalization.
Main Results:
- Low serum potassium (<4 mEq/L) was associated with increased all-cause mortality (HR, 1.22; 95% CI, 1.04-1.44; p=0.014).
- Low-normal serum potassium (3.5-3.9 mEq/L) also showed a significant association with mortality (HR, 1.19; 95% CI, 1.00-1.41; p=0.049).
- Neither low nor low-normal serum potassium levels were significantly associated with all-cause hospitalization.
Conclusions:
- In elderly ambulatory chronic heart failure patients, low and low-normal serum potassium levels are associated with increased mortality.
- These potassium levels were not associated with increased all-cause hospitalization.
- Findings highlight the prognostic significance of potassium levels in older HF populations.
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.
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