Impaired saltiness perception contributes to higher sodium intake among patients with chronic kidney disease: a cross-sectional two-center study.

Objective: Dietary sodium restriction is important in the prognosis of patients with chronic kidney disease (CKD). The association between saltiness perception and sodium intake among CKD patients is unclear, and the factors that influence saltiness are also not fully understood. We evaluated saltiness perception in CKD patients employing a cost-effective saltiness perception test using sodium solutions and evaluated the association between saltiness perception, sodium intake and influencing factors.

Design and methods: CKD outpatients not undergoing dialysis were enrolled from two medical centers and underwent saltiness perception tests together with 24-hour urine collections to measure daily sodium intake. Participants who perceived saltiness using the test solution containing 25 mM sodium were regarded to have "preserved" saltiness perception while those unable to perceive saltiness were regarded as having "impaired" saltiness perception.

Results: Of the total 132 participants, the median daily sodium intake was 3.36 g (range; 0.51 to 9.95 g/day), and 43 (32.6%) were ex- or current smokers. When participants were divided into 3 groups (G) according to daily sodium intake level: low (G1; 0.51 to 2.61 g/day), middle (G2; 2.62 to 3.99 g/day) and high (G3; 4.06 to 9.95 g/day), there was an obvious difference in impaired saltiness perception between three groups: 6.8% in G1, 50.0% in G2 and 86.4% in G3 (p-value = 8.035 x 10^-14, Cochran-Armitage test). In a multiple regression analysis in which the saltiness perception was adopted as a subjective variable, smoking habit (ex- or current smoker) and nonadherence to dietary sodium restriction were identified as significant explanatory variables.

Conclusion: We revealed the clear relationship between higher daily sodium intake and impaired saltiness perception that is related to nonadherence to dietary sodium restriction and smoking habit; both of which could be intervened by nutritional counselling and public health education.