![]() You crave that midnight snack not because you're hungry, but because you're tired – and eating instead of sleeping makes you even more tired. Without a good night's rest, you make more of the 'hunger hormone' ghrelin and less of the 'satiety hormone' leptin, which drives an appetite for carbohydrate-rich food. Obesity is one of the world's largest public health issues, and being overweight is associated with poor-quality sleep. ![]() Sleep helps maintain a strong immune system too, and reduces the risk of cardiovascular diseases. ![]() In humans, it seems to be especially important for cognitive functions such as learning and memory: in one study, school teachers were able to predict which students had slept 45 minutes less than normal (per night over a week). Sleep is vital for virtually all animals. Gringras' team concluded: 'Ideally future software design could be better optimized when night-time use is anticipated, and hardware should allow an automatic "bedtime mode" that shifts blue and green light emissions to yellow and red as well as reduce backlight/light intensity.' Both approaches were effective at reducing blue light. The researchers then tested two strategies for limiting light emissions: wearing orange-tinted (blue-blocking) safety glasses, and using an app called 'Kids Sleep Dr' that adjusts a device's color palette. This confirmed that modern screens give-off blue wavelengths. In his recent study, Gringras and colleagues compared light emitted from various devices – an iPhone 5s, iPad Air and Kindle Paperwhite e-reader – when displaying text. NEXT: Why a 'bedtime mode' improves your health. "People fall asleep later and they wake-up with more inertia – more grogginess, probably reflecting the fact that you've not slept for quite as long as you need." Work pressures force adults to get an early start or finish late, for example, while children catch-up on social media before school so they aren't behind on gossip.Īs a result, Gringras argues that there's no slack in the system. The artificial light problem is made worse by our busy modern lives, which push sleep patterns to the limit. Using a laptop in bed (Image CC 0: Pixabay) And while the invention of the light bulb has had many benefits for human society, it's also created some adverse effects on our health. Stimulation from artificial light at inappropriate times stops the body clock from becoming synchronized with the outside world. "You'd need to drink a lot of coffee to postpone sleep onset and melatonin production as much as bright light exposure would." "It's as powerful a neurological stimulus as taking a drug," says Gringras, adding that preventing melatonin release can delay sleep by an hour (on average). ![]() Modern displays are high-contrast, brighter and more energy-efficient, which allows for high-resolution screens and a longer battery life.īut while backlit displays are good for gadgets, they're bad for the body, because looking at bright LEDs makes your brain think that it's daytime. These receptors are only designed to detect light, and they're especially sensitive to the 'cool' blue-green wavelengths and aren't really stimulated by the 'warm' red-orange light at the end of the visible spectrum.įire and older incandescent bulbs mainly emit orange-y wavelengths that don't interfere with sleep much, whereas newer technology uses light-emitting diodes (LEDs) with bluer light. But there's also a third type of cell: 'intrinsically photosensitive retinal ganglion cells'. Human physiology and behavior during a 24-hour cycle (Image: Wikimedia)Įyes sense light via photoreceptor cells in the retina, using 'cones' for colour vision and 'rods' for black-and-white. The rise and fall of melatonin levels over a 24-hour period influences your physiology and behavior, including blood pressure and general alertness. The sleep hormone is destroyed by sunlight, so melatonin is sometimes known as a ' Dracula hormone'. This master body clock then prompts the nearby pineal gland to release melatonin, a hormone that circulates in the blood and tells your cells it's time to sleep. Light is detected by the eye, which relays that stimulus to the 'suprachiasmatic nucleus' within the hypothalamus, a cluster of neurons in the middle of the brain. Clocks can be adjusted by an external cue, what biologists call a zeitgeber (German for 'time-giver'), and sunlight is nature's most powerful cue. But assuming Night Shift works in the right way, saying that warmer colors are 'easier on your eyes' is misleading: night mode doesn't reduce eye strain – it helps stop light from affecting the brain.īody clocks have circadian rhythms – internal cycles that last about 24 hours ( circa diem is Latin for 'around a day').
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