Individuals with an objective decrease in salivary flow (objective dry mouth) may not be aware of subjective dry mouth (xerostomia). However, no clear evidence exists to explain the discordance between subjective and objective dry mouth. Therefore, this cross-sectional study aimed to assess the prevalence of xerostomia and decreased salivary flow among community-dwelling elderly adults. In addition, this study assessed several potential demographic and health status determinants of the discrepancy between xerostomia and reduced salivary flow. The 215 participants in this study were community-dwelling older people aged 70 years and above who underwent dental health examinations between January-February 2019. Symptoms of xerostomia were collected in the form of a questionnaire. The unstimulated salivary flow rate (USFR) was measured by a dentist using visual inspection. The stimulated salivary flow rate (SSFR) was measured using the Saxon test. We identified 19.1% of participants as having mild-severe USFR decline with xerostomia and 19.1% as having mild-severe USFR decline without xerostomia. Additionally, 26.0% of participants had low SSFR and xerostomia, and 40.0% had low SSFR without xerostomia. Except for the age trend, no factors could be associated with the discordance between USFR measurement and xerostomia. Furthermore, no significant factors were associated with the discordance between the SSFR and xerostomia. However, females were significantly associated (OR = 2.608, 95% CI = 1.174–5.791) with low SSFR and xerostomia, as compared to males. Age was a factor that was also significantly associated (OR = 1.105, 95% CI = 1.010–1.209) with low SSFR and xerostomia. Our findings indicate that approximately 20% of the participants had low USFR without xerostomia, and 40% had low SSFR without xerostomia. This study showed that age, sex, and the number of medications may not be factors in the discrepancy between the subjective feeling of dry mouth and reduced salivary flow.

In fields using functional near-infrared spectroscopy (fNIRS), there is a need for an easy-to-understand method that allows visual presentation and rapid analysis of data and test results. This preliminary study examined whether deep learning (DL) could be applied to the analysis of fNIRS-derived brain activity data. To create a visual presentation of the data, an imaging program was developed for the analysis of hemoglobin (Hb) data from the prefrontal cortex in healthy volunteers, obtained by fNIRS before and after tooth clenching. Three types of imaging data were prepared: oxygenated hemoglobin (oxy-Hb) data, deoxygenated hemoglobin (deoxy-Hb) data, and mixed data (using both oxy-Hb and deoxy-Hb data). To differentiate between rest and tooth clenching, a cross-validation test using the image data for DL and a convolutional neural network was performed. The network identification rate using Hb imaging data was relatively high (80‒90%). These results demonstrated that a method using DL for the assessment of fNIRS imaging data may provide a useful analysis system.

The aim of this study was to validate the possibility of using functional Near-Infrared Spectroscopy (fNIRS) to measure changes in cerebral blood flow in response to a hand being placed on a participant’s back, and to identify the areas of enhanced activity in the brain. Nineteen female adult volunteers participated in the study. An experienced school nurse touched the center of the participant’s back between the shoulder blades with the palm of her hand. Cerebral blood volume dynamics were measured with a 52-channel fNIRS system. Significantly higher oxygenated hemoglobin (oxy-Hb) concentration levels were recorded by channels 11, 14, 21, 22, 24, 32, 35, 45, 46, and 49 during the touching period than during the resting period. These channels indicated enhanced activity in the supramarginal gyrus, the middle frontal gyrus, the superior temporal gyrus, and the inferior frontal gyrus. The ability to detect changes in cerebral blood flow using this method indicates the possibility of measuring changes in cerebral blood flow using fNIRS when a person is touched on the back. fNIRS has been shown to be useful for studying the effects of touch.

Background: The time from mastication to swallowing is used as an indicator of masticatory and swallowing functions. However, there have been no reports on reasonable eating times associated with eating satisfaction. Clarifying the reasonable time for eating and drinking to achieve eating satisfaction will indicate the level of mastication and swallowing functions that contributes to maintaining an individual’s quality of life. Objective: This study aimed to determine the time from food intake to the end of swallowing that is associated with eating satisfaction. Methods: A cross-sectional survey of 437 community-dwelling older people was conducted. Mastication and swallowing times (SST-MST) were measured using the Saku-Saku Test with a 2 g rice cracker. Food intake difficulty and eating satisfaction were evaluated using a questionnaire. The association between the SST-MST and the difficulty in eating food or eating satisfaction was assessed by sensitivity, specificity, Youden index, sensitivity–specificity ratio, positive likelihood ratio, negative likelihood ratio, odds ratio, and 95% confidence interval. Results: Most indices indicated that a cutoff point of 25 s on the SST-MST was associated with not having difficulty in eating food items. Moreover, when the SST-MST cutoff was set to 25 s, all indices showed a favorable association with eating satisfaction. Conclusions: In community-dwelling older people in their 70s and 80s, an SST-MST of about 25 s for 2 g of rice crackers was modestly associated with eating satisfaction.

Few studies have reported nationwide changes in dental visit patterns during the COVID-19 pandemic. This study aimed to clarify the impact of the COVID-19 pandemic on the type of dental treatment in Japan based on trends in the frequency of dental clinic visits per month and dental expenses per month or day. An interrupted time-series analysis was performed to examine changes in data from the national database before and after the first declaration of a state of emergency. Between March and April 2020, the monthly dental expenses per patient (MDEPP) increased by approximately JPY 950 (JPY) (p < 0.001) in patients aged ≤64 years and ≥65 years. Dental expenses per treatment (DEPT) increased by approximately JPY 300–400 (p < 0.001) in both age groups. After April 2020, the slope of the regression line for DEPT significantly increased in those aged ≤64 years (p < 0.001) and in those ≥65 years (p = 0.024). The number of treatments per month (NTPM) increased after the declaration of a state of emergency. However, the decreasing trend in the regression line for NTPM was stronger in those aged ≤64 years (p < 0.001). The MDEPP, DEPT, and NTPM showed an increasing trend during the first state of emergency compared to those observed in the previous year. The proportion of patients with relatively severe disease may have increased because patients with mild disease refrained from undergoing dental examinations. These results suggest changes in the type of dental treatment during the COVID-19 pandemic.