| 1. |
Taisuke Eto, Shingo Kitamura, Kana Nishimura, Kota Takeoka, Yuki Nishimura, Sang-il Lee, Michihiro Ohashi, Akiko Shikano, Shingo Noi, Shigekazu Higuchi, Circadian phase advances in children during camping life according to the natural light-dark cycle, Journal of Physiological Anthropology, 10.1186/s40101-022-00316-x, 41, 1, 2022.12. |
| 2. |
Michihiro Ohashi, Sang-il Lee, Taisuke Eto, Nobuo Uotsu, Chie Tarumizu, Sayuri Matsuoka, Shinobu Yasuo, Shigekazu Higuchi, Intake of l-serine before bedtime prevents the delay of the circadian phase in real life, Journal of Physiological Anthropology, 10.1186/s40101-022-00306-z, 41, 1, 2022.08, Background
It has been shown in laboratory experiments using human subjects that ingestion of the non-essential amino acid L-serine before bedtime enhances the advance of circadian phase induced by light exposure the next morning. In the present study, we tested the effect of ingestion of L-serine before bedtime on circadian phase in real life and whether its effect depends on the initial circadian phase.
Methods
The subjects were 33 healthy male and female university students and they were divided into an L-serine group (n = 16) and a placebo group (n = 17). This study was conducted in a double-blind manner in autumn and winter. After a baseline period for 1 week, the subjects took 3.0 g of L-serine or a placebo 30 min before bedtime for 2 weeks. Saliva was collected twice a week at home every hour under a dim light condition from 20:00 to 1 h after habitual bedtime. Dim light melatonin onset (DLMO) was used as an index of phase of the circadian rhythm.
Results
DLMO after intervention was significantly delayed compared to the baseline DLMO in the placebo group (p = 0.02) but not in the L-serine group. There was a significant difference in the amount of changes in DLMO between the two groups (p = 0.04). There were no significant changes in sleeping habits after intervention in the two groups. There were significant positive correlations between advance of DLMO and DLMO before intervention in the L-serine group (r = 0.53, p Conclusions
Our findings suggest that intake of L-serine before bedtime for multiple days might attenuate the circadian phase delay in the real world and that this effect does not depend on the initial circadian phase.. |
| 3. |
Shigekazu Higuchi, Yandan Lin, Jingjing Qiu, Yichi Zhang, Michihiro Ohashi, Sang-il Lee, Shingo Kitamura, Akira Yasukouchi, Is the use of high correlated color temperature light at night related to delay of sleep timing in university students? A cross-country study in Japan and China, Journal of Physiological Anthropology, 10.1186/s40101-021-00257-x, 40, 1, 7-7, 2021.12, Abstract
Background
Blue-enriched white light at night has the potential to delay the circadian rhythm in daily life. This study was conducted to determine whether the use of high correlated color temperature (CCT) light at home at night is associated with delay of sleep timing in university students.
Methods
The survey was conducted in 2014–2015 in 447 university students in Japan and 327 students in China. Habitual sleep timing and type of CCT light at home were investigated by using a self-administered questionnaire. The Japanese students were significantly later than the Chinese students in bedtime, wake time, and midpoint of sleep. They were asked whether the lighting in the room where they spend most of their time at night was closer to warm color (low CCT) or daylight color (high CCT). The amount of light exposure level during daily life was measured for at least 1 week by the use of a light sensor in 60 students in each country.
Results
The percentages of participants who used high CCT lighting at night were 61.6% for Japanese students and 80.8% for Chinese students. Bedtime and sleep onset time on school days and free days were significantly later in the high CCT group than in the low CCT group in Japan. The midpoint of sleep in the high CCT group was significantly later than that in the low CCT group on free days but not on school days. On the other hand, none of the sleep measurements on school days and free days were significantly different between the high CCT and low CCT groups in China. Illuminance level of light exposure during the night was significantly higher in Japanese than in Chinese, but that in the morning was significantly higher in China than in Japan.
Conclusions
The use of high CCT light at night is associated with delay of sleep timing in Japanese university students but not in Chinese university students. The effects of light at night on sleep timing and circadian rhythm may be complicated by other lifestyle factors depending on the country.
. |
| 4. |
Taisuke Eto, Michihiro Ohashi, Kotaro Nagata, Nakyeong Shin, Yuki Motomura, Shigekazu Higuchi, Crystalline lens transmittance spectra and pupil sizes as factors affecting light-induced melatonin suppression in children and adults, OPHTHALMIC AND PHYSIOLOGICAL OPTICS, 10.1111/opo.12809, 2021.07. |
| 5. |
Eto T,Petteri Teikari,Raymond P. Najjar,Nishimura Y,Motomura Y,Kuze M Higuchi S, A Purkinje image-based system for an assessment of the density and transmittance spectra of the human crystalline lens in vivo, scientific reports, 10.1038/s41598-020-73541-y, 2020.10, A method for rapid and objective assessment of ocular lens density and transmittance is needed for research and clinical practice. The aim of this study was to determine whether the Purkinje image-based technique can be used for objective and accurate quantification of spectral density and transmittance of ocular media (the mainly crystalline lens) in visible light. Twenty-six individuals (10 young, 9 middle-aged and 7 older individuals) participated in this study. Spectral lens density was evaluated by detecting the intensity of the IVth Purkinje image for different wavelengths. Subsequently, optical density index (ODI), the area under the curve in the lens density spectrum, was calculated and ODIs were compared with clinical lens opacification scales assessed subjectively using a slit lamp. Spectral lens transmittance was estimated from the lens density spectrum. Lens densities were higher in the short wavelength region of the visible spectrum across all age groups. ODI was highly correlated with the clinical opacification scale, while lens transmittance decreased with aging. Our results showed that spectral transmittance of the human crystalline lens can be easily estimated from optical density spectra evaluated objectively and rapidly using the Purkinje image-based technique. Our results provide clinicians and scientists with an accurate, rapid and objective technique for quantification of lens transmittance.. |
| 6. |
Sang‐il Lee,Kouhei Matsumori,Kana Nishimura,Yuki Nishimura,Yuki Ikeda,Taisuke Eto,Shigekazu Higuchi, Melatonin suppression and sleepiness in children exposed to blue‐enriched white LED lighting at night, Physiological Reports, 2018.12, Light‐induced melatonin suppression in children is reported to be more sensitive to white light at night than that in adults; however, it is unclear whether it depends on spectral distribution of lighting. In this study, we investigated the effects of different color temperatures of LED lighting on children's melatonin secretion during the night. Twenty‐two healthy children (8.9 ± 2.2 years old) and 20 adults (41.7 ± 4.4 years old) participated in this study. A between‐subjects design with four combinations, including two age groups (adults and children) and the two color temperature conditions (3000 K and 6200 K), was used. The experiment was conducted for two consecutive nights. On the first night, saliva samples were collected every hour under a dim light condition ( |
