Cross-sectional Associations of Serum Sodium, Potassium, and Chloride with Cognition in Patients on Hemodialysis: The Osaka Dialysis Complication Study (ODCS).

RATIONALE &

OBJECTIVES

Cognitive function is impaired in patients with chronic kidney disease, particularly in those undergoing hemodialysis, although the precise mechanisms are not well understood. This cross-sectional study examined the possible relationship between serum electrolyte levels and cognitive function in patients receiving maintenance hemodialysis.

STUDY

DESIGN

Cross-sectional study.

SETTINGS &

PARTICIPANTS

Eligible patients were selected from the participants of the Osaka Dialysis Complication Study, a multicenter study conducted in Japan.

EXPOSURES: Serum sodium, potassium, and chloride levels.

OUTCOMES: Cognitive function assessed by the Modified Mini-Mental State examination (3MS) which was mathematically transformed to 3MS' to follow a normal distribution.

ANALYTICAL APPROACH: Multivariable-adjusted linear regression analysis.

RESULTS

For this study, 1,207 patients were selected. Their median age, 3MS score, serum sodium, potassium, and chloride concentrations were 67 (IQR, 60-74) years, 91 (IQR, 82-97) points, 139 (IQR, 137-141) mEq/L, 4.7 (IQR, 4.2-5.2) mEq/L, and 102 (IQR, 99-105) mEq/L, respectively. After adjustment, sodium (P = 0.23) or potassium (P = 0.38) were not associated with the 3MS score, whereas serum chloride was positively associated with the 3MS score (3MS', regression coefficient 0.100 [0.062, 0.138] per 1 IQR (6 mEq/L), P < 0.001) independently of potential confounders. The positive association between serum chloride and cognition was consistent in subgroup analysis. The difference in the 3MS score by 1 IQR of chloride was comparable to that of the difference by 7 years of age.

LIMITATIONS: Causality cannot be determined because of the cross-sectional design.

CONCLUSIONS

This study revealed that serum chloride level was a novel factor independently associated with cognitive performance in patients on maintenance hemodialysis, suggesting an unrecognized role of chloride in cognition.