Abstract: We found two studies involving 162 adults that met our inclusion criteria. Neither of the two studies included children. The duration of treatment and length of sessions varied between studies from four sessions delivered weekly, to four sessions over two months. Similarly, length of sessions varied slightly from one 60-minute session and three 45-minute sessions to four 30-minute sessions. The control interventions were healthy lifestyle advice in both studies. One study contributed HRQoL data, using the Leicester Cough Questionnaire (LCQ), and we judged the quality of the evidence to be low using the GRADE approach. Data were reported as between-group difference from baseline to four weeks (MD 1.53, 95% confidence interval (CI) 0.21 to 2.85; participants = 71), revealing a statistically significant benefit for people receiving a physiotherapy and speech and language therapy intervention (PSALTI) versus control. However, the difference between PSALTI and control was not observed between week four and three months. The same study provided information on SAEs, and there were no SAEs in either the PSALTI or control arms. Using the GRADE approach we judged the quality of evidence for this outcome to be low. Data were also available for our prespecified secondary outcomes. In each case data were provided by only one study, therefore there were no opportunities for aggregation; we judged the quality of this evidence to be low for each outcome. A significant difference favouring therapy was demonstrated for: objective cough counts (ratio for mean coughs per hour on treatment was 59% (95% CI 37% to 95%) relative to control; participants = 71); symptom score (MD 9.80, 95% CI 4.50 to 15.10; participants = 87); and clinical improvement as defined by trialists (OR 48.13, 95% CI 13.53 to 171.25; participants = 87). There was no significant difference between therapy and control regarding subjective measures of cough (MD on visual analogue scale of cough severity: −9.72, 95% CI −20.80 to 1.36; participants = 71) and cough reflex sensitivity (capsaicin concentration to induce five coughs: 1.11 (95% CI 0.80 to 1.54; participants = 49) times higher on treatment than on control). One study reported data on adverse events, and there were no adverse events reported in either the therapy or control arms of the study. The paucity of data in this review highlights the need for more controlled trial data examining the efficacy of SLT interventions in the management of UCC. Although a large number of studies were found in the initial search as per protocol, we could include only two studies in the review. In addition, this review highlights that endpoints vary between published studies.  The improvements in HRQoL (LCQ) and reduction in 24-hour cough frequency seen with the PSALTI intervention were statistically significant but short-lived, with the between-group difference lasting up to four weeks only. Further studies are required to replicate these findings and to investigate the effects of SLT interventions over time. It is clear that SLT interventions vary between studies. Further research is needed to understand which aspects of SLT interventions are most effective in reducing cough (both objective cough frequency and subjective measures of cough) and improving HRQoL. We consider these endpoints to be clinically important. It is also important for future studies to report information on adverse events. Because of the paucity of data, we can draw no robust conclusions regarding the efficacy of SLT interventions for improving outcomes in unexplained chronic cough. Our review identifies the need for further high-quality research, with comparable endpoints to inform robust conclusions.

Plain-language summary: We found two relevant studies to include in the review. Both studies were randomised controlled trials (a type of study in which participants are assigned to one of two or more treatment groups using a random method) in which participants had a diagnosis of UCC. Participants received either an intervention including SLT techniques or 'healthy lifestyle advice' as a control group. We chose to use health-related quality of life and serious adverse events to judge whether SLT is a useful intervention. Only one of the studies comparing SLT to usual care reported data about quality of life (using a questionnaire). After four weeks, participants in the study who were receiving the SLT treatment, physiotherapy and speech and language therapy intervention (PSALTI), had on average an improvement in their quality of life compared to people in the control group. However, this benefit compared to control was short-lived and disappeared after four weeks. This means that although the treatment appeared to work in the shorter term, it may not improve quality of life in the longer term compared to usual care. We also looked for information about side effects or harms of the treatment. The same study reported that no one experienced serious side effects or harms during the study. Other ways of measuring the impact of SLT were also considered, and in each case relevant data were only provided by one study. An improvement in objective cough counts (using a cough monitor), symptoms (using symptom scores), and clinical improvement was shown with SLT compared to controls. The included trials reported no difference for other secondary outcomes such as subjective measures of cough or cough reflex sensitivity (measured in the laboratory using airway irritants). The small number of high-quality, relevant studies found in this review means that we cannot be sure of the overall benefits of SLT in the management of UCC. Improvements in health-related quality of life were associated with the PSALTI intervention over a short period in one study, but further research is required to replicate this finding. Overall, more controlled trials are required to fully examine the potential of SLT for the management of UCC.