The frequency of spontaneous swallowing is useful for screening of dysphagia in acute stroke. Low levels of substance P (SP) in saliva attenuate the swallowing reflex. The aim of this study was to determine the relationship between the frequency of spontaneous swallowing and salivary SP levels. In 40 subjects, saliva was collected within 72 h after stroke onset and salivary SP levels were measured using ELISA kit at a later date. The frequency of spontaneous swallowing was measured over 1 h using a microphone placed on the neck. Pneumonia was diagnosed by the presence of pyrexia and at least two respiratory problems of four categories (sputum, cough or breathing pattern, breath sound, and gas change). The presence of detectable levels of SP in the saliva was confirmed in 17 patients (high SP group), whereas the level was below the detection limit of the ELISA kit in 23 patients (low SP group). The frequency of spontaneous swallowing was significantly lower in low SP group (16.1 ± 11.6 per hour) than in the high SP group (30.4 ± 20.4, p = 0.016). As the result of multiple regression analysis, salivary SP levels were correlated with frequency of spontaneous swallowing independently of age, NIHSS, and GCS. The incidence of pneumonia was significantly higher in the low than high SP group (p < 0.001). In conclusion, the frequency of spontaneous swallowing was decreased in acute stroke patients with low salivary SP levels. Salivary SP levels can be potentially a useful biomarker of risk of stroke-associated pneumonia in the acute stage.
Dysphagia Substance P Aspiration pneumonia Acute stroke Deglutition Stroke-associated pneumonia
This is a preview of subscription content, log in to check access.
This study was funded partly by Tokyo Metropolitan Clinical Research Grant (No. H27040308).
Compliance with Ethical Standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Cohen DL, Roffe C, Beavan J, et al. Post-stroke dysphagia: a review and design considerations for future trials. Int J Stroke. 2016;11:399–411.CrossRefPubMedGoogle Scholar
Nishino T, Takizawa K, Yokokawa N, Hiraga K. Depression of the swallowing reflex during sedation and/or relative analgesia produced by inhalation of 50% nitrous oxide in oxygen. Anesthesiology. 1987;67:995–8.CrossRefPubMedGoogle Scholar
Arai T, Yasuda Y, Takaya T, Toshima S, Kashiki Y, Yoshimi N, Fujiwara H. ACE inhibitors and symptomless dysphagia. Lancet. 1998;352:115–6.CrossRefPubMedGoogle Scholar
Tanaka N, Nohara K, Okuno K, Kotani Y, Okazaki H, Matsumura M, Sakai T. Development of a swallowing frequency meter using a laryngeal microphone. J Oral Rehabil. 2012;39:411–20.CrossRefPubMedGoogle Scholar
Takahashi K, Groher ME, Michi K. Methodology for detecting swallowing sounds. Dysphagia. 1994;9:54–62.PubMedGoogle Scholar
Lyden P, Brott T, Tilley B, et al. Improved reliability of the NIH stroke scale using video training. NINDS TPA stroke study group. Stroke. 1994;25:2220–6.CrossRefPubMedGoogle Scholar
Adams HP Jr, Bendixen BH, Kappelle LJ, et al. Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of org 10172 in acute stroke treatment. Stroke. 1993;24:35–41.CrossRefPubMedGoogle Scholar
Wilson JT, Hareendran A, Hendry A, et al. Reliability of the modified Rankin scale across multiple raters: benefits of a structured interview. Stroke. 2005;36:777–81.CrossRefPubMedGoogle Scholar
Crary MA, Mann GD, Groher ME. Initial psychometric assessment of a functional oral intake scale for dysphagia in stroke patients. Arch Phys Med Rehabil. 2005;86:1516–20.CrossRefPubMedGoogle Scholar
Smith CJ, Kishore AK, Vail A, et al. Diagnosis of stroke-associated pneumonia: recommendations from the pneumonia in stroke consensus group. Stroke. 2015;46:2335–40.CrossRefPubMedGoogle Scholar
Faul F, Erdfelder E, Lang AG, et al. G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007;39:175–91.CrossRefPubMedGoogle Scholar
Suntrup-Krueger S, Bittner S, Recker S, Meuth SG, Warnecke T, Suttrup I, Marian T, Dziewas R. Electrical pharyngeal stimulation increases substance P level in saliva. Neurogastroenterol Motil. 2016;28:855–60.CrossRefPubMedGoogle Scholar
He M, Ohrui T, Azumi M, Ida S, Sasaki H. Depressed involuntary swallowing and risk of pneumonia. J Am Geriatr Soc. 2004;52:1032–3.CrossRefPubMedGoogle Scholar