Tohoku J. Exp. Med., 2016 October, 240(2)

Gustatory Salivation Is Associated with Body Mass Index, Daytime Sleepiness, and Snoring in Healthy Young Adults

SATOSHI IZUMI,¹ GUANG HONG,² KOH IWASAKI,³ MASAYUKI IZUMI,¹ YUSUKE MATSUYAMA,⁴ MIREI CHIBA,¹ TAKASHI TODA¹ and TADA-AKI KUDO¹

¹Division of Oral Physiology, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
²Liaison Center for Innovative Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
³Ishinomaki-Ogatsu Municipal Clinic, Ishinomaki, Miyagi, Japan
⁴Department of International Community and Oral Health, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan

The taste detection system for oral fatty acid may be related to obesity. In addition, sleep is intrinsically and closely related to food intake and metabolism. However, the association of gustatory salivation with body mass index (BMI), daytime sleepiness, or sleep habits is largely unknown. Therefore, we evaluated the relationship between gustatory salivation and BMI, Epworth sleepiness scale (ESS, a daytime sleepiness scale) or sleep habits among 26 healthy young individuals (20 males and 6 females; mean age: 26.0 ± 4.3 years). We also measured the saliva flow rate (SFR) that was induced by gum-chewing or each of three prototypical tastants (acetic acid, sucrose, and NaCl). Further, the SFR was induced by fatty acid, provided as oleic acid (OA) homogenized in non-fat milk. All participants showed normal rates of salivation during resting and gum-chewing states. The increase in the SFR induced by OA, but not by each of the three tastants, was associated with BMI. Moreover, both daytime sleepiness level and frequency of snoring were associated with the increase in the SFR induced by NaCl. These results suggest that BMI is associated with salivation induced by oral fatty acid exposure. Additionally, the regulatory mechanism for the NaCl-induced salivation reflex may have a relationship with impairments of the respiratory control system that are related to snoring during sleep and lead to daytime sleepiness because of insufficient sleep. Thus, measurement of gustatory salivation might contribute to the evaluation and prevention of obesity and sleep-related breathing disorders.

keywords —— body mass index; Epworth sleepiness scale; fatty acid; gustatory salivation; sleep habit

© 2016 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2016, 240, 153-165

Correspondence: Tada-aki Kudo, Division of Oral Physiology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan.

e-mail: tkudo@m.tohoku.ac.jp