Normative Values of the Repetitive Saliva Swallow Test and Clinical Factors Affecting the Test Scores in Healthy Adults

The Repetitive Saliva Swallow Test (RSST) is a screening test for oropharyngeal dysphagia during which the subject is asked to perform as many empty swallows as possible in 30 s. Previous validation studies found a cutoff value of 3 > swallows as pathological. The aims of this study were to establish the normative values of the RSST and to examine the effect of clinical factors on RSST scores in healthy adults. A cross-sectional study of 280 adults. An equal number of females and males were recruited for each decade of life, ages 20 to 90 years. Patients reporting swallowing difficulties, history of neurologic disorders, or head and neck surgery or radiation were excluded. Data collected included RSST scores, number and type of comorbidities, number of prescribed medications, body mass index, smoking habits, and self-assessment xerostomia questionnaire. The mean RSST score for the entire cohort was 7.01 +/- 2.86. Males had a higher RSST score (7.6 +/- 3.04 compared to 6.47 +/- 2.56, p = 0.001). Age showed an inverse correlation with RSST scores (Pearson's Correlation Coefficient (PCC) = -0.463, p < 0.0001), as well as body mass index, BMI (PCC = -0.2, p < 0.0001), number of co-morbidities (PCC=-0.344, p < 0.0001) and number of prescribed medications (PCC= -0.425, p < 0.0001). Self-reported amount of saliva positively correlated (PCC = 1.05, p = 0.04) with RSST scores. A multivariate logistic regression analysis was performed. Age, sex, BMI, and number of prescribed medications were found as significant independent factors on RSST scores. RSST scores in healthy adults decline with age and are lower in females, individuals taking multiple medications and with higher BMI. Mean RSST for all age groups did not fall beneath the previously established pathological cut-off.