Effect of TRP-Stimulating Compounds to Reduce Swallowing Response Time in the Elderly: A Systematic Review

There is still controversy on evidence supporting compounds that stimulate the transient receptor potential cation channel (TRP) receptor, which can reduce the latency of swallowing reflex. This systematic review aims to evaluate the effectiveness of TRP-stimulating compounds to reduce swallowing reflex time in the elderly. We searched the following databases: PubMed, EMBASE, OVID, Central, Scopus, ISI, CINALH, LILACS, CRD database, and Open grey until June 1st, 2019. We included randomized controlled trials (RCTs) which compared swallowing time between TRP-stimulating compounds and placebo or no treatment in population aged more than 60 years old. We assessed bias using the Cochrane risk of bias tool. Three authors independently screened and selected studies. Quality assessment and data extraction were performed by two authors independently. Of 363 reviews, we included four RCTs. Two RCTs used black pepper, one RCT used capsaicinoids, and the other one used capsaicin ointment to stimulate the TRPV1 receptor. All of the studies were assessed at unclear bias except the study, which used capsaicin ointment with assessed as low risk of bias. Meta-analysis could not be done in this study due to the different baseline characteristics and definition of swallowing reflex time. This review demonstrates the potential effect of TRPV1-stimulating compounds to reduce swallowing response time in the elderly were remains unclear. Most studies had an unclear bias. Further larger and well-designed RCTs are needed to draw robust conclusions.