Method: Systematic searches of the PubMed, EBSCOhost, Web of Science, Cochrane, EMBASE, Dissertations and Theses, and Scopus databases were conducted to identify potentially relevant studies, published between 1966 and June 2013. Studies that examined unstimulated and stimulated whole salivary flow rates in healthy human subjects aged 18 to 98 years were included. A standardized mean difference and 95% confidence interval (CI) were calculated for whole unstimulated and stimulated salivary flow rates between young and elderly individuals using Hedge’s g. A random effects model was used. To address the potential influence of medication use on age-related salivary flow rate effects, the analysis was repeated on the subgroup of studies that included only medication-free subjects.
Result: Forty-six articles met the systematic review inclusion criteria. In both the unstimulated and stimulated conditions, salivary flow rates were reduced in the elderly group compared with the young group (Hedge’s g=0.604, 95% CI 0.449 – 0.759, p<0.0001 and Hedge’s g=0.336, 95% CI 0.010 – 0.661, p=0.043, respectively). These effects were observed for both male and female subjects. When the analysis was limited to studies of medication-free subjects (N=25), unstimulated whole salivary flow rate remained significantly lower in the elderly group compared with the young group (Hedge’s g=0.585, 95% CI 0.355 – 0.814, p<0.0001), while stimulated whole salivary flow rate was not significantly different between groups.
Conclusion: Unstimulated and stimulated whole salivary flow rates are significantly decreased in elderly subjects of both genders. While medication use may explain the age-related decrease in stimulated whole salivary flow rate, medication use does not appear to account for the age-related decrease in unstimulated whole salivary flow rate.