Exploring the relationship between plasma substance P and glottal incompetence in the elderly

We speculated that increased blood-plasma levels of Substance P may serve as an indicator of glottal incompetence, which is usually indicated by reduced maximum phonation time. We performed an initial study to test the plausibility of this hypothesis. Patients with dysphonia caused by glottal incompetence were asked to perform vocal exercises for six months to reduce glottal incompetence and we compared the plasma concentration of Substance P before and after the vocal exercise to detect correlation between maximum phonation time and plasma concentration of Substance P. Based on the results, we further hypothesized that patients exhibiting dysphonia with maximum phonation time less than 14 s, in particular less than 10 sec, caused by glottal incompetence may have increased plasma concentration of Substance P with the results of elevated thresholds of cough reflex associated with subclinical aspiration in airways. Further study is needed on patients with decreased Substance P levels, with low scores on Activities of Daily Living and who are hospitalized with aspiration pneumonia.