Objective: The objective of this study is to update prevalence estimates for xerostomia and salivary gland hypofunction (SGH) among older adults through a systematic review and meta-analysis.

Background: Dry mouth is common among older adults but is inconsistently assessed and reported. Xerostomia and SGH represent distinct conditions with different diagnostic approaches, leading to heterogeneity in prevalence estimates.

Materials and methods: A systematic literature search of Medline (PubMed) and Web of Science was conducted from January 2018 to March 2025. This was supplemented by manual backward citation tracking of the foundational review to identify all eligible pre-2018 epidemiological studies. Only studies utilizing population-representative samples of adults aged 50 years and older with defined diagnostic criteria were included. Risk of bias was formally assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Tool for Prevalence Studies. Pooled prevalence estimates were calculated using random-effects meta-analyses. (PROSPERO: CRD420251009592).

Results: A total of 37 studies-encompassing over 1.6 million participants-met the inclusion criteria. The pooled global prevalence of xerostomia among older adults was 21% (95% CI: 19%-23%). For SGH, the pooled prevalence measured via UWS was 12% (95% CI: 4%-24%), whereas SWS yielded a prevalence of 13% (95% CI: 3%-28%). High heterogeneity was observed across all analyses. Differences in diagnostic thresholds and saliva collection methods contributed to the observed variability.

Conclusion: This updated meta-analysis confirms that xerostomia affects around one-fifth of older adults, while SGH is less common, depending on the diagnostic criteria used. Future research should focus on improving diagnostic consistency and sample representativeness to enable more consistent and robust estimates, and thereby better guide prevention and care in geriatric oral health.