Serum Bicarbonate Concentration and Cause-Specific Mortality: The National Health and Nutrition Examination Survey...

To assess the association between serum bicarbonate concentration and cause-specific mortality in the US general population.

A total of 31,195 individuals enrolled in the National Health and Nutrition Examination Survey between 1999 and 2010 were followed for a median 6.7 (interquartile range, 3.7-9.8) years. Cause-specific mortality was defined as cardiovascular, malignancy, and noncardiovascular/nonmalignancy causes. Cox proportional hazards adjusted for demographics, comorbidities, medications, and renal function were used to test the association between baseline serum bicarbonate and the outcomes of interest.

Of the 2798 participants who died, 722 had a cardiovascular- and 620 had a malignancy-related death. Compared with participants with serum bicarbonate 22 to 26 mEq/L, those with a level below 22 mEq/L had an increased hazard of all-cause and malignancy-related mortality (hazard ratio [HR], 1.54; 95% CI, 1.30-1.83; and HR, 1.46; 95% CI 1.00-2.13, respectively). The hazard for cardiovascular mortality was increased by 8% with each 1 mEq/L increase in serum bicarbonate above 26 mEq/L (HR, 1.08; 95% CI, 1.01-1.15). The findings were consistent in participants with or without chronic kidney disease, with no significant interactions observed.

In a large cohort of US adults, serum bicarbonate concentration level below 22 mEq/L was associated with malignancy-related mortality, whereas a concentration above 26 mEq/L was associated with cardiovascular mortality. Further studies to evaluate potential mechanisms for the differences in cause-specific mortality are warranted.