The effect of gum chewing on xerostomia and salivary flow rate in elderly and medically compromised subjects: a systematic review and meta-analysis

Abstract

Background: Xerostomia negatively affects quality of life. Symptoms include oral dryness; thirst; difficulty speaking, chewing, and swallowing food; oral discomfort; mouth soft tissue soreness and infections; and rampant tooth decay. The objective of this systematic review and meta-analysis was to investigate if gum chewing is an intervention that results in objective improvements in salivary flow rates and subjective relief from xerostomia.

Method: We searched electronic databases including Medline, Scopus, Web of Science, Embase, Cochrane Library (CDSR and Central), Google Scholar and the citations of review papers (last searched 31/03/23). The study populations included: 1) elderly people with xerostomia (> 60 years old, any gender, and severity of xerostomia), and 2) medically compromised people with xerostomia. The intervention of interest was gum chewing. Comparisons included gum chewing vs. no gum chewing. The outcomes included salivary flow rate, self-reported xerostomia, and thirst. All settings and study designs were included. We conducted a meta-analysis on studies where measurements of unstimulated whole salivary flow rate for both a gum chewing, and no gum chewing intervention (daily chewing of gum for two weeks or longer) were reported. We assessed risk of bias using Cochrane's RoB 2 and ROBINS-I tools.

Results: Nine thousand six hundred and two studies were screened and 0.26% (n = 25) met the inclusion criteria for the systematic review. Two of the 25 papers had a high overall risk of bias. Of the 25 papers selected for the systematic review, six met the criteria to be included in the meta-analysis which confirmed a significant overall effect of gum on saliva flow outcomes compared to control (SMD = 0.44, 95% CI: 0.22-0.66; p = 0.00008; I² = 46.53%).

Conclusions: Chewing gum can increase unstimulated salivary flow rate in elderly and medically compromised people with xerostomia. Increasing the number of days over which gum is chewed increases the improvement in the rate of salivation. Gum chewing is linked with improvements in self-reported levels of xerostomia (although it is noted that no significant effects were detected in five of the studies reviewed). Future studies should eliminate sources of bias, standardise methods to measure salivary flow rate, and use a common instrument to measure subjective relief from xerostomia.

Study registration: PROSPERO CRD42021254485.

Keywords: Chewing gum; Dry mouth; Mastication; Meta-analysis; Salivary flow rate; Systematic review; Xerostomia.

Fig. 1

Overview of the systematic review on the effect of gum chewing on xerostomia and salivary flow rate in elderly and medically compromised subjects (as per PRISMA statement)

Fig. 2

Risk of bias summary using the revised Cochrane risk of bias tool for randomised trials (RoB 2). Five domains are reported: D1 (randomisation process); D2 (deviations from the intended interventions); D3 (missing outcome data); D4 (measurement of the outcome) and D5 (selection of the reported result). ‘ + ’ low risk of bias; ‘!’ some concerns, and ‘- ‘ high risk of bias

Fig. 3

Risk of bias summary using the revised Cochrane risk of bias tool for cross-over trials (RoB 2). Six domains are reported: D1 (randomisation process); DS (bias arising from period and carryover effects); D2 (deviations from the intended interventions); D3 (missing outcome data); D4 (measurement of the outcome) and D5 (selection of the reported result). ‘ + ’ low risk of bias; ‘!’ some concerns, and ‘- ‘ high risk of bias

Fig. 4

Risk of bias summary using the revised Cochrane risk of bias tool for non-randomised studies—of Interventions (ROBINS-I). Seven domains are reported: D1 (confounding); D2 (selection of participants into the study); D3 (classification of interventions); D4 (deviations from intended interventions); D5 (missing data); D6 (measurement of outcomes) and D7 (selection of the reported result). ‘ + ’ low risk of bias; ‘!’ some concerns, and ‘- ‘ high risk of bias

Fig. 5

Forest plot

Fig. 6

Funnel plot

Fig. 7

Sensitivity analysis

Fig. 8

Meta-regression bubble plot