Evaluation of Spontaneous Swallow Frequency in Healthy People and Those With, or at Risk of Developing, Dysphagia: A Systematic Review and Meta-Analysis.

Dysphagia is a common, and frequently undetected, complication of many neurological disorders and of sarcopoenia in ageing persons. However it is difficult to detect dysphagia clinically until the point of visible aspiration, and there are relatively few trained speech and language therapists, whose time and remit are limited to those with obvious disorders. Reduction in spontaneous swallowing frequency (SSF) has been mooted as a possible proxy for dysphagia. We therefore conducted a systematic review of the literature to describe SSF in both the healthy population, and in disease specific populations, in order to assess its utility as a screening tool to identify dysphagia.

Methods

We searched Medline, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials databases. Metadata were extracted, collated, and analysed via a random effects model to give quantitative insight.

Results

Three hundred and twelve articles were retrieved, with 19 meeting inclusion and quality criteria. Heterogeneity between studies was high (I2 = 98%), in part, due to the variety of methods for swallow identification reported. The mean SSF in Healthy younger groups was 0.98/min [CI: 0.78; 1.23]. In the Parkinson’s groups mean SSF was 0.59/min [0.41; 0.85]. Mean SSF in Healthy older, Higher risk and Dysphagic populations were similar (0.21/min [0.12; 0.37], 0.26/min [0.14; 0.85]), (0.27/min [0.17; 0.43] respectively).

Conclusions

SSF is a novel, non-invasive clinical variable which warrants further explorations as to its potential to identify persons at risk of dysphagia. Larger, well-conducted studies are needed to develop objective, standardised methods for detecting SSF, and develop normative values in healthy populations.