THE RELATIONSHIP BETWEEN DEHYDRATION AND PAROTID SALIVARY-GLAND FUNCTION IN YOUNG AND OLDER HEALTHY-ADULTS

Background. Saliva is essential for the maintenance of oral health. Th e primary constituent of saliva is water and, traditionally decreased body water homeostasis has been linked with salivary dysfunction. This is consistent with the greater prevalence of dehydration and salivary gland dysfunction among the elderly. However, this association betwee n dehydration and salivary dysfunction has never been tested using obj ective criteria The purpose of this study was to determine the effect of body dehydration upon parotid salivary flow rates in young and olde r healthy adults. Methods. Twelve young (20-40 years) and 12 older (60 -80 years) healthy subjects abstained From food and beverage intake fo r 24 h (dehydration) and then underwent intravenous rehydration to rep lace all lost weight. Unstimulated and stimulated parotid salivary flo w rates, weight, hematocrit, hemoglobin, serum sodium, plasma protein, creatinine, serum, and urine osmolality values were assessed at basel ine, 24 h, and 1 h after the completion of rehydration. Results. All s ubjects experienced a significant decrease in weight and increased lev els of hematocrit, hemoglobin, plasma protein, and creatinine during d ehydration with few age-related differences. intravenous fluid replace ment increased weight and decreased hematocrit, hemoglobin, plasma pro tein, and creatinine back to baseline values, demonstrating that subje cts were metabolically rehydrated. Unstimulated (young and older, p =. 0001) and stimulated (young, p >.05; older, p =.03) parotid Row rates decreased during the 24-h dehydration period, yet did not completely r eturn (young and older unstimulated, p <.001; young and older stimulat ed, p >.05) to baseline values after rehydration. Conclusions. These f indings suggest that body dehydration is associated with decreased par otid salivary gland Row rates, and that these changes are generally ag e-independent in healthy adults. Furthermore, although subjects were m etabolically rehydrated, unstimulated salivary Bow rates remained sign ificantly lower than baseline levels.