Nutritional status modifies cause-specific mortality risk associated with higher serum calcium levels in patients undergoing hemodialysis: The Q-cohort Study.

BACKGROUND & AIMS: Higher serum calcium and phosphate levels are important risk factors for morbidity and mortality in patients undergoing hemodialysis. While studies have shown that malnutrition blunts the impact of hyperphosphatemia on mortality risk, the effect of malnutrition or protein-energy wasting on the mortality risk associated with higher serum calcium levels remains unclear.

METHODS

This prospective, multicenter, observational cohort study followed 3049 patients undergoing maintenance hemodialysis for 4 years. The exposures were serum calcium levels and surrogate markers of nutritional status (serum albumin, serum creatinine levels, and the malnutrition-inflammation complex syndrome score), and the primary outcome was all-cause mortality, with cardiovascular and non-cardiovascular mortality analyzed as secondary outcomes. Mortality risks were estimated using Cox proportional hazards regression models.

RESULTS

During a median follow-up of 3.5 years, 639 patients died. Higher serum calcium levels were associated with increased all-cause, cardiovascular, non-cardiovascular, infection-related, and malignancy-related mortality in the multivariable-adjusted models. When patients were stratified into four groups based on the combination of serum calcium and nutritional markers, higher serum calcium levels were associated with increased all-cause and cardiovascular mortality, regardless of nutritional status. However, the risk of non-cardiovascular mortality associated with higher calcium levels was diminished in well-nourished patients.

CONCLUSIONS

Nutritional status may differentially modify the risk of cause-specific mortality associated with elevated serum calcium levels in patients undergoing hemodialysis.