The effect of dehydration on parotid salivary gland function

Dehydration is common in the elderly, and has been traditionally linked with salivary hypofunction. This study examined the effect of dehydration on parotid salivary flow rates. Twelve young and 12 older healthy subjects abstained from food and fluid intake for 24 hrs (dehydration) and then underwent i.v. rehydration proportional to the amount of weight lost. Unstimulated and stimulated parotid flow rates, weight, hematocrit and hemoglobin values were assessed at baseline and 24 hrs, and 1 hr after completion of rehydration. All subjects experienced decreases in weight and increases in hematocrit and hemoglobin during dehydration. I.v. fluids caused weight gain and decreased hematocrit and hemoglobin, demonstrating that subjects were metabolically rehydrated. During dehydration, unstimulated flow rates decreased in young (p < 0.001) and older (p < 0.001) subjects, and stimulated flow rates decreased in young (p > 0.05) and older (p = 0.03) subjects. While flow rates increased with rehydration, they remained lower than baseline levels. No age or gender differences were detected for salivary data. These findings suggest that dehydration may cause decreased parotid flow rates, independent of age in healthy adults.