Scientific+Report
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KAIST researchers find sleep delays more prevalent in countries of particular culture than others
Sleep has a huge impact on health, well-being and productivity, but how long and how well people sleep these days has not been accurately reported. Previous research on how much and how well we sleep has mostly relied on self-reports or was confined within the data from the unnatural environments of the sleep laboratories.
So, the questions remained: Is the amount and quality of sleep purely a personal choice? Could they be independent from social factors such as culture and geography?
< From left to right, Sungkyu Park of Kangwon National University, South Korea; Assem Zhunis of KAIST and IBS, South Korea; Marios Constantinides of Nokia Bell Labs, UK; Luca Maria Aiello of the IT University of Copenhagen, Denmark; Daniele Quercia of Nokia Bell Labs and King's College London, UK; and Meeyoung Cha of IBS and KAIST, South Korea >
A new study led by researchers at Korea Advanced Institute of Science and Technology (KAIST) and Nokia Bell Labs in the United Kingdom investigated the cultural and individual factors that influence sleep. In contrast to previous studies that relied on surveys or controlled experiments at labs, the team used commercially available smartwatches for extensive data collection, analyzing 52 million logs collected over a four-year period from 30,082 individuals in 11 countries. These people wore Nokia smartwatches, which allowed the team to investigate country-specific sleep patterns based on the digital logs from the devices.
< Figure comparing survey and smartwatch logs on average sleep-time, wake-time, and sleep durations. Digital logs consistently recorded delayed hours of wake- and sleep-time, resulting in shorter sleep durations. >
Digital logs collected from the smartwatches revealed discrepancies in wake-up times and sleep-times, sometimes by tens of minutes to an hour, from the data previously collected from self-report assessments. The average sleep-time overall was calculated to be around midnight, and the average wake-up time was 7:42 AM. The team discovered, however, that individuals' sleep is heavily linked to their geographical location and cultural factors. While wake-up times were similar, sleep-time varied by country. Individuals in higher GDP countries had more records of delayed bedtime. Those in collectivist culture, compared to individualist culture, also showed more records of delayed bedtime. Among the studied countries, Japan had the shortest total sleep duration, averaging a duration of under 7 hours, while Finland had the longest, averaging 8 hours.
Researchers calculated essential sleep metrics used in clinical studies, such as sleep efficiency, sleep duration, and overslept hours on weekends, to analyze the extensive sleep patterns. Using Principal Component Analysis (PCA), they further condensed these metrics into two major sleep dimensions representing sleep quality and quantity. A cross-country comparison revealed that societal factors account for 55% of the variation in sleep quality and 63% of the variation in sleep quantity.
Countries with a higher individualism index (IDV), which placed greater emphasis on individual achievements and relationships, had significantly longer sleep durations, which could be attributed to such societies having a norm of going to bed early. Spain and Japan, on the other hand, had the bedtime scheduled at the latest hours despite having the highest collectivism scores (low IDV). The study also discovered a moderate relationship between a higher uncertainty avoidance index (UAI), which measures implementation of general laws and regulation in daily lives of regular citizens, and better sleep quality.
Researchers also investigated how physical activity can affect sleep quantity and quality to see if individuals can counterbalance cultural influences through personal interventions. They discovered that increasing daily activity can improve sleep quality in terms of shortened time needed in falling asleep and waking up. Individuals who exercise more, however, did not sleep longer. The effect of exercise differed by country, with more pronounced effects observed in some countries, such as the United States and Finland. Interestingly, in Japan, no obvious effect of exercise could be observed. These findings suggest that the relationship between daily activity and sleep may differ by country and that different exercise regimens may be more effective in different cultures.
This research published on the Scientific Reports by the international journal, Nature, sheds light on the influence of social factors on sleep. (Paper Title "Social dimensions impact individual sleep quantity and quality" Article number: 9681)
One of the co-authors, Daniele Quercia, commented: “Excessive work schedules, long working hours, and late bedtime in high-income countries and social engagement due to high collectivism may cause bedtimes to be delayed.”
Commenting on the research, the first author Shaun Sungkyu Park said, "While it is intriguing to see that a society can play a role in determining the quantity and quality of an individual's sleep with large-scale data, the significance of this study is that it quantitatively shows that even within the same culture (country), individual efforts such as daily exercise can have a positive impact on sleep quantity and quality."
"Sleep not only has a great impact on one’s well-being but it is also known to be associated with health issues such as obesity and dementia," said the lead author, Meeyoung Cha. "In order to ensure adequate sleep and improve sleep quality in an aging society, not only individual efforts but also a social support must be provided to work together," she said. The research team will contribute to the development of the high-tech sleep industry by making a code that easily calculates the sleep indicators developed in this study available free of charge, as well as providing the benchmark data for various types of sleep research to follow.
2023.07.07 View 4874 -
Attachable Skin Monitors that Wick the Sweat Away
- A silicone membrane for wearable devices is more comfortable and breathable thanks to better-sized pores made with the help of citric acid crystals. -
A new preparation technique fabricates thin, silicone-based patches that rapidly wick water away from the skin. The technique could reduce the redness and itching caused by wearable biosensors that trap sweat beneath them. The technique was developed by bioengineer and professor Young-Ho Cho and his colleagues at KAIST and reported in the journal Scientific Reports last month.
“Wearable bioelectronics are becoming more attractive for the day-to-day monitoring of biological compounds found in sweat, like hormones or glucose, as well as body temperature, heart rate, and energy expenditure,” Professor Cho explained. “But currently available materials can cause skin irritation, so scientists are looking for ways to improve them,” he added.
Attachable biosensors often use a silicone-based compound called polydimethylsiloxane (PDMS), as it has a relatively high water vapour transmission rate compared to other materials. Still, this rate is only two-thirds that of skin’s water evaporation rate, meaning sweat still gets trapped underneath it.
Current fabrication approaches mix PDMS with beads or solutes, such as sugars or salts, and then remove them to leave pores in their place. Another technique uses gas to form pores in the material. Each technique has its disadvantages, from being expensive and complex to leaving pores of different sizes.
A team of researchers led by Professor Cho from the KAIST Department of Bio and Brain Engineering was able to form small, uniform pores by crystallizing citric acid in PDMS and then removing the crystals using ethanol. The approach is significantly cheaper than using beads, and leads to 93.2% smaller and 425% more uniformly-sized pores compared to using sugar. Importantly, the membrane transmits water vapour 2.2 times faster than human skin.
The team tested their membrane on human skin for seven days and found that it caused only minor redness and no itching, whereas a non-porous PDMS membrane did.
Professor Cho said, “Our method could be used to fabricate porous PDMS membranes for skin-attachable devices used for daily monitoring of physiological signals.”
“We next plan to modify our membrane so it can be more readily attached to and removed from skin,” he added.
This work was supported by the Ministry of Trade, Industry and Energy (MOTIE) of Korea under the Alchemist Project.
Image description:
Smaller, more uniformly-sized pores are made in the PDMS membrane by mixing PDMS, toluene, citric acid, and ethanol. Toluene dilutes PDMS so it can easily mix with the other two constituents. Toluene and ethanol are then evaporated, which causes the citric acid to crystallize within the PDMS material. The mixture is placed in a mould where it solidifies into a thin film. The crystals are then removed using ethanol, leaving pores in their place.
Image credit:
Professor Young-Ho Cho, KAIST
Image usage restrictions:
News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only.
Publication:
Yoon, S, et al. (2021) Wearable porous PDMS layer of high moisture permeability for skin trouble reduction. Scientific Reports 11, Article No. 938. Available online at https://doi.org/10.1038/s41598-020-78580-z
Profile:
Young-Ho Cho, Ph.D
Professor
mems@kaist.ac.kr
https://mems.kaist.ac.kr
NanoSentuating Systems Laboratory
Department of Bio and Brain Engineering
https://kaist.ac.kr
Korea Advanced Institute of Science and Technology (KAIST)
Daejeon, Republic of Korea
(END)
2021.02.22 View 10902 -
'Engineered Bacterium Produces 1,3-Diaminopropane'
A research team led by Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering at KAIST reported, for the first time, the production of 1,3-diaminopropane via fermentation of an engineered bacterium.
1,3-Diaminopropane is a three carbon diamine, which has a wide range of industrial applications including epoxy resin and cross-linking agents, as well as precursors for pharmaceuticals, agrochemicals, and organic chemicals. It can also be polymerized with dicarboxylic acids to make polyamides (nylons) for use as engineering plastics, medical materials, and adhesives.
Traditionally, 1,3-diaminopropane is derived from petroleum-based processes. In effort to address critical problems such as the depletion of petroleum and environmental issues inherent to the petroleum-based processes, the research team has developed an Escherichia coli (E. coli) strain capable of producing 1,3-diaminopropane. Using this technology, 1,3-diaminopropane can now be produced from renewable biomass instead of petroleum.
E. coli as found in nature is unable to produce 1,3-diaminopropane. Metabolic engineering, a technology to transform microorganisms into highly efficient microbial cell factories capable of producing chemical compounds of interest, was utilized to engineer the E. coli strain. First, naturally existing metabolic pathways for the biosynthesis of 1,3-diaminopropane were introduced into a virtual cell in silico to determine the most efficient metabolic pathway for the 1,3-diaminopropane production. The metabolic pathway selected was then introduced into an E. coli strain and successfully produced 1,3-diaminopropane for the first time in the world.
The research team applied metabolic engineering additionally, and the production titer of 1,3-diaminopropane increased about 21 fold. The Fed-batch fermentation of the engineered E. coli strain produced 13 grams per liter of 1,3-diaminoproapne. With this technology, 1,3-diaminopropane can be produced using renewable biomass, and it will be the starting point for replacing the current petroleum-based processes with bio-based processes.
Professor Lee said, “Our study suggested a possibility to produce 1,3-diaminopropane based on biorefinery. Further study will be done to increase the titer and productivity of 1,3-diaminopropane.”
This work was published online in Scientific Reports on August 11, 2015.
Reference: Chae, T.U. et al. "Metabolic engineering of Escherichia coli for the production of 1,3-diaminopropane, a three carbon diamine," Scientific Reports:
http://www.nature.com/articles/srep13040
This research was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries from Ministry of Science, ICT and Future Planning (MSIP) through the National Research Foundation (NRF) of Korea.
Figure 1: Metabolic engineering strategies for 1,3-diaminopropane production using C4 pathway
Figure 2: Fed-batch fermentation profiles of two final engineered E. coli strains
2015.08.12 View 10106 -
Professor YongKeun Park Produces Undergraduate Students with International Achievements
Three undergraduate students under the supervision of Professor YongKeun Park from the Department of Physics, KAIST, have published papers in globally renowned academic journals.
The most recent publication was made by YoungJu Jo, a senior in physics. Jo’s paper entitled “Angle-resolved light scattering of individual rod-shaped bacteria based on Fourier transform light scattering” was published in the May 28th edition of Scientific Reports.
Analyzing bacteria is a very important task in the field of health and food hygiene, but using the conventional biochemical methods of analysis takes days. However, observation with Jo’s newly developed method using light scattering analyzes bacteria within a matter of seconds.
SangYeon Cho from the Department of Chemistry also published papers in Cell (2012) and Nature (2013), respectively, under the guidance of Professor Park. SangYeon Cho’s outstanding research achievements were recognized by Harvard and MIT. He was accepted with a full scholarship to Harvard-MIT Health Sciences and Technology Graduate School. He will begin his graduate studies at Harvard-MIT this September.
Last March, SeoEun Lee from the Department of Biology was the recipient of the Best Paper Award by the Optical Society of Korea. She plans to pursue a doctoral degree at the College of Physicians and Surgeons, Columbia University in New York.
Professor Park said, “Undergraduate students, who are learning a variety of subjects concurrently, are at the most creative time of their lives. KAIST has offered many opportunities to undergraduate students to partake in various research programs.”
- Picture (a) and (b): Rod-shaped bacteria’s phase image and light-scattering patterns
- Picture (c): Quantitative analysis to illustrate the extraction of information from bacteria
2014.06.03 View 11334 -
Technology Developed to Control Light Scattering Using Holography
Published on May 29th Nature Scientific Reports online
Recently, a popular article demonstrated that an opaque glass becomes transparent as transparent tape is applied to the glass. The scientific principle is that light is less scattered as the rough surface of the opaque glass is filled by transparent tape, thereby making things behind the opaque glass look clearer.
Professor Yong-Keun Park from KAIST’s Department of Physics, in a joint research with MIT Spectroscopy Lab, has developed a technology to easily control light scattering using holography. Their results are published on Nature’s Scientific Reports May 29th online edition.
This technology allows us to see things behind visual obstructions such as cloud and smoke, or even human skin that is highly scattering, optically thick materials. The research team applied the holography technology that records both the direction and intensity of light, and controlled light scattering of obstacles lied between an observer and a target image. The team was able to retrieve the original image by recording the information of scattered light and reflecting the light precisely to the other side.This phenomenon is known as “phase conjugation” in physics. Professor Park’s team applied phase conjugation and digital holography to observe two-dimensional image behind a highly scattering wall. “This technology will be utilized in many fields of physics, optics, nanotechnology, medical science, and even military science,” said Professor Park. “This is different from what is commonly known as penetrating camera or invisible clothes.” He nevertheless drew the line at over-interpreting the technology, “Currently, the significance is on the development of the technology itself that allows us to accurately control the scattering of light."
Figure I. Observed Images
Figure II. Light Scattering Control
2013.07.19 View 7804