July is the month with the worst sleep qualityJust when we thought the rainy season had begun, a scorching summer arrived early. On June 17th, the Kanto region observed its first "intensely hot day" of the year, with over 50 locations registering temperatures of 35°C or higher for the first time this year. *1 With such intense heat continuing, fatigue accumulates during the day, and it becomes difficult to sleep at night, leading to numerous challenges in maintaining one's health. Therefore, getting good quality sleep is becoming increasingly important. A study analyzed sleep data over a year from users of Brain Sleep Coin, a sleep tracking tool developed and sold by Brain Sleep, to see how sleep changes each month. It was found that the duration of deep sleep in July was 7.5 minutes shorter compared to December, the month with the longest deep sleep. A decrease in deep sleep duration leads to a decline in sleep quality, and the sleep score calculated in this study showed that July had the lowest result. There are two main reasons for the decline in summer sleep scores: the first is a decrease in sleep quality, and the second is a reduction in sleep duration. *1 tenki.jp - Today, June 17th, historically high temperatures for June. The number of intensely hot days and sweltering days is the highest this year. https://tenki.jp/forecaster/deskpart/2025/06/17/34161.html *2 An original analysis of the relationship with seasons from one year of sleep measurement data. https://prtimes.jp/main/html/rd/p/000000256.000046684.html Cause ①: Decline in sleep quality: Hot and humid tropical nightsTo get deep sleep, the key is to lower your core body temperature immediately after falling asleep. When your core body temperature, which is high during the day, decreases at night, you can sleep deeply during the first 90 minutes after falling asleep, which determines sleep quality. However, during the summer, it is difficult for core body temperature to decrease due to the effects of outside temperature and humidity. According to the Ministry of the Environment's "Study on Room Temperature, Humidity, and Core Body Temperature *3," it has been found that core body temperature is less likely to drop when room temperature and humidity are high (red line). Furthermore, even when the room temperature remained constant, a decrease in humidity led to a drop in core body temperature (gray line). This shows that high room temperature and humidity affect core body temperature, and that controlling humidity is also important. In 2024, the monthly average temperature exceeded 25°C from July to September, and the monthly average humidity exceeded 50% except for February. *4 While temperature tends to be the focus in summer, a characteristic of Japanese summers is high humidity. According to data from the Japan Meteorological Agency, the average humidity in Tokyo from June to August has increased by approximately 15% compared to 20 years ago *5, making it important to control both temperature and humidity. *3 Ministry of the Environment, "Report on Environmental Impact, etc., of Heat Island Countermeasures"*4 Japan Meteorological Agency: Past weather data (2024 national monthly average temperatures)*5 Japan Meteorological Agency: Past weather data (Tokyo average humidity in June-August 2004 and 2024)Cause ②: Reduced sleep duration: Extended daylight hoursSleep is related to "sleep pressure." When you are exposed to morning sunlight, the secretion of melatonin, a sleep hormone, stops and sleep pressure is suppressed. After about 13 to 15 hours, secretion begins again, and sleep pressure increases, making you naturally feel sleepy. If you go to bed when sleep pressure is high, you can fall asleep smoothly. However, in summer, the sun rises early, and melatonin secretion stops early, making it easier to wake up early. Along with this, melatonin secretion at night also starts earlier, and sleep pressure increases earlier. Since our daily routine doesn't change, there's a mismatch with when we actually go to sleep, leading to difficulty falling asleep and a decline in sleep quality. Three tips to improve summer sleep quality that you can implement right away!1. Temperature and Humidity (Indoors, in bed)The optimal room temperature in summer is 24-28°C (humidity 50-60%), and the temperature inside the bed is 33±1°C (humidity 50±5%). It is advisable to leave the air conditioner on to cool the walls warmed during the day and maintain an appropriate temperature at night. Also, it is recommended to wear long-sleeved clothing and use an appropriate duvet so that the wind does not directly hit your body. 2. Utilize appropriate bedding To control the temperature and humidity inside the bed, it is good to choose materials that are highly breathable and moisture-absorbent. Also, if you share a bed, it is recommended that each person use their own duvet. There are individual differences in comfortable temperatures, and there is a concern that one person might hog the blanket. 3. Light controlIn summer, the sun rises early, awakening the brain and causing you to wake up early. Melatonin secretion, which promotes sleep, begins 14-16 hours after exposure to light, so you'll feel sleepy earlier. Consider implementing your "personal summer time" to intentionally shift your daily rhythm earlier, or use blackout curtains or eye masks to adjust the light. "Brain Sleep Comforter Perfect Cool EX" equipped with triple cooling technologyThe ultimate cold comforter for a cool night's sleep, thanks to three cooling technologies. This unique summer comforter boasts ultimate contact cooling at approximately 260% of the maximum standard value, moisture-absorbing cooling that achieves a maximum of -7.7°C, and sustained cooling that revives the cooling sensation when the comforter separates from the body due to tossing and turning during sleep. Perfect coolThe triple cooling technology of contact cooling, moisture-absorbing cooling, and sustained cooling allows you to spend comfortable summer nights. The ultimate coolness that lasts all night supports your sleep. We developed the yarn and fabric from scratch, achieving a q-max value (a measure of contact cooling) of 0.524, which is the highest level at approximately 260% of the standard value of 0.2 (slightly cool to the touch). Just by touching it, it exhibits ultimate contact cooling. Equipped with innovative moisture-absorbing cooling technology that converts moisture absorbed during sleep into a cooling sensation. Achieves a maximum temperature drop of -7.7°C. By absorbing and releasing moisture, it maintains a non-stuffy humidity level in the bed. The fibers of the comforter are blended with PCM, an innovative cooling technology developed for space suits, encapsulated in microcapsules. While common contact-cooling bedding loses its cooling properties once the absorbed heat reaches saturation, the Brain Sleep Comforter Perfect Cool EX has a sustained cooling function that revives the cooling sensation when the comforter separates from the body due to tossing and turning during sleep. Perfect comfortWith its perfect 4-layer structure, and a reversible design that can be used from the rainy season to late summer. The two-layer breathable structure of the dry side adds a gentle contact cooling function to a smooth feel. You can choose the comfortable coolness that suits your preferences and environment. Perfect cleanNo cover needed, always clean with home washing. It features antibacterial and deodorizing processing to prevent bacterial growth in summer, and also eliminates unpleasant sweat odors, ensuring cleanliness. Product Name: Brain Sleep Comforter Perfect Cool EXPrice (tax included): Single 24,200 yen, Semi-double 29,700 yen, Double 35,200 yenURL: https://brain-sleep.com/products/comforter_perfectcoolex"Brain Sleep Eye Mask Hot + Cool" helps you control light and support your ideal summer sleep rhythmMaintain your sleep rhythm with blackout featuresIt adopts an auto-fit material that conforms to the skin by sensing body temperature and blocks light leaking from the gap around the nose. In summer, sunrise tends to be earlier, leading to earlier wake-up times. By using an eye mask to manage your sleep and wake-up times, and by living according to your ideal sleep rhythm, you can ensure sufficient sleep. Product Name: Brain Sleep Eye Mask Hot + CoolPrice (tax included): 6,930 yen (with 1 gel pack)URL: https://brain-sleep.com/products/eyemask
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