The role of oral dryness in interdialytic weight gain by diabetic and non-diabetic haemodialysis patients

Background. Factors influencing the percentage of daily interdialytic weight gain (IDWG%) and their interactions in haemodialysis (HD) patients have not been well-defined, especially in diabetic patients. We analysed contributing factors for the increase of IDWG%, particularly xerostomia (oral dryness), among diabetic and non-diabetic HD patients. Methods. We collected 3 month prospective data in 184 stable HD patients (116 non-diabetic and 68 diabetic), including assessments of xerostomia by 100 mm visual analog scales (VASs), and the unstimulated whole salivary (UWS) flow rate was measured in 91 patients by a spitting method. Results. Diabetic patients have higher IDWG% (P = 0.042) and VAS oral dryness score (P = 0.021), whereas, have lower UWS (P = 0.032). In non-diabetic patients, the VAS oral dryness score, age, Kt/V and blood urea nitrogen (BUN) level correlated independently with IDWG%. In diabetic patients, the haemoglobin A 1C (HbA_1C) correlated significantly with IDWG% after controlling for age, Kt/V and BUN level; however, when VAS oral dryness score was introduced into the regression model, the effect of HbA_1C became marginally significant (P = 0.073) while the VAS oral dryness score became significantly correlated with IDWG%. The increases in IDWG% per unit change in VAS oral dryness score did not show significant difference between the non-diabetic and total diabetic patients; however, it was larger in patients with HbA_1C≥9%. Conclusions. Xerostomia plays a significant role in increasing IDWG% among diabetic and non-diabetic HD patients. In diabetic patients, the increased IDWG% associated with the increasing HbA_1C level is largely dependent on the severity of xerostomia, and we speculate that insulin deficiency may operate synergistically with xerostomia in increasing IDWG% in patients with HbA_1C ≥9%.