
How much does your phone’s blue light really delay your sleep? Relax, it’s just 2.7 minutes
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It’s one of the most pervasive messages about technology and sleep. We’re told bright, blue light from screens prevents us falling asleep easily. We’re told to avoid scrolling on our phones before bedtime or while in bed. We’re sold glasses to help filter out blue light. We put our phones on “night mode” to minimise exposure to blue light.
But what does the science actually tell us about the impact of bright, blue light and sleep? When our group of sleep experts from Sweden, Australia and Israel compared scientific studies that directly tested this, we found the overall impact was close to meaningless. Sleep was disrupted, on average, by less than three minutes.
We showed the message that blue light from screens stops you from falling asleep is essentially a myth, albeit a very convincing one.
Instead, we found a more nuanced picture about technology and sleep.

What we did
We gathered evidence from 73 independent studies with a total of 113,370 participants of all ages examining various factors that connect technology use and sleep.
We did indeed find a link between technology use and sleep, but not necessarily what you’d think.
We found that sometimes technology use can lead to poor sleep and sometimes poor sleep can lead to more technology use. In other words, the relationship between technology and sleep is complex and can go both ways.
How is technology supposed to harm sleep?
Technology is proposed to harm our sleep in a number of ways. But here’s what we found when we looked at the evidence:
- bright screen light – across 11 experimental studies, people who used a bright screen emitting blue light before bedtime fell asleep an average of only 2.7 minutes later. In some studies, people slept better after using a bright screen. When we were invited to write about this evidence further, we showed there is still no meaningful impact of bright screen light on other sleep characteristics including the total amount or quality of sleep
- arousal is a measure of whether people become more alert depending on what they’re doing on their device. Across seven studies, people who engaged in more alerting or “exciting” content (for example, video games) lost an average of only about 3.5 minutes of sleep compared to those who engaged in something less exciting (for example, TV). This tells us the content of technology alone doesn’t affect sleep as much as we think
- we found sleep disruption at night (for example, being awoken by text messages) and sleep displacement (using technology past the time that we could be sleeping) can lead to sleep loss. So while technology use was linked to less sleep in these instances, this was unrelated to being exposed to bright, blue light from screens before bedtime.
Which factors encourage more technology use?
Research we reviewed suggests people tend to use more technology at bedtime for two main reasons:
- to “fill the time” when they’re not yet sleepy. This is common for teenagers, who have a biological shift in their sleep patterns that leads to later sleep times, independent of technology use.
- to calm down negative emotions and thoughts at bedtime, for apparent stress reduction and to provide comfort.
There are also a few things that might make people more vulnerable to using technology late into the night and losing sleep.
We found people who are risk-takers or who lose track of time easily may turn off devices later and sacrifice sleep. Fear of missing out and social pressures can also encourage young people in particular to stay up later on technology.
What helps us use technology sensibly?
Last of all, we looked at protective factors, ones that can help people use technology more sensibly before bed.
The two main things we found that helped were self-control, which helps resist the short-term rewards of clicking and scrolling, and having a parent or loved one to help set bedtimes.

Why do we blame blue light?
The blue light theory involves melatonin, a hormone that regulates sleep. During the day, we are exposed to bright, natural light that contains a high amount of blue light. This bright, blue light activates certain cells at the back of our eyes, which send signals to our brain that it’s time to be alert. But as light decreases at night, our brain starts to produce melatonin, making us feel sleepy.
It’s logical to think that artificial light from devices could interfere with the production of melatonin and so affect our sleep. But studies show it would require light levels of about 1,000-2,000 lux (a measure of the intensity of light) to have a significant impact.
Device screens emit only about 80-100 lux. At the other end of the scale, natural sunlight on a sunny day provides about 100,000 lux.
What’s the take-home message?
We know that bright light does affect sleep and alertness. However our research indicates the light from devices such as smartphones and laptops is nowhere near bright or blue enough to disrupt sleep.
There are many factors that can affect sleep, and bright, blue screen light likely isn’t one of them.
The take-home message is to understand your own sleep needs and how technology affects you. Maybe reading an e-book or scrolling on socials is fine for you, or maybe you’re too often putting the phone down way too late. Listen to your body and when you feel sleepy, turn off your device.
Chelsea Reynolds, Casual Academic/Clinical Educator and Clinical Psychologist, College of Education, Psychology and Social Work, Flinders University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Longans vs Lychees – Which is Healthier?
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Our Verdict
When comparing longans to lychees, we picked the lychees.
Why?
These two fruits are more closely related than they look from the outside, both being members of the soapberry family. However, there are some differences:
In terms of macros, longans have more protein while lychees have more carbs, and they are equal on fiber, giving longans the lower glycemic index. They’re both good, but longans nominally take the win on this one.
When it comes to vitamins, longans have more of vitamins B1, B2, and C, while lychees have more of vitamins B3, B6, B9, E, K, and choline, making for a respectable win for lychees in this category.
In the category of minerals, longans have more copper and potassium, while lychees have more calcium, iron, manganese phosphorus, and zinc. Thus, a win for lychees here too.
It’s worth looking at polyphenols too—lychees have around 10x more, which is notable.
Adding up the categories makes for an overall win for lychees, but by all means enjoy either or both! Diversity is good.
Want to learn more?
You might like to read:
Replacing Sugar: Top 10 Anti-Inflammatory Sweet Foods ← longans and lychees both make the list
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Everyday Products With Unexpected Skincare Benefits
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Dr. Andrea Suarez shares some tips that sound crazy but work. How many would you use?
Not made for purpose
Items to consider:
- Laundry detergent: no, not directly on your skin, but it makes a big difference if you increase the frequency of washing your bedding, towels, and washcloths, to reduce dust mites, demodex mites, and bacterial contamination that can aggravate conditions like rosacea, folliculitis, or atopic dermatitis.
- Household bleach: a dilute (!) bleach bath (¼–½ cup of regular bleach per bathtub of lukewarm water, soak for 10–20 minutes) can help decolonize Staphylococcus aureus, reduce eczema flare-ups, and calm bacterial folliculitis on the body; always rinse and moisturize after.
- Plastic wrap (e.g. Saran): after bathing, apply petroleum jelly to dry areas like your heels, feet, knees, or elbows, then wrap with plastic wrap for 10–20 minutes to lock in moisture and smooth rough skin; can also be used on a wall to apply lotion to your back.
- Superglue (cyanoacrylate adhesive): use a small drop to seal painful skin fissures or hangnails—keeps the edges together for faster healing and prevents infection; never use it on your face or lips, though.
- Duct tape: applying duct tape to plantar warts and removing it every six days can mechanically exfoliate, trigger an immune response, and help clear warts more quickly.
- Binder clips: used as inexpensive compression tools on healed earlobes after keloid removal to prevent recurrence—wear about eight hours daily for several months. Perhaps while you’re sleeping, if you don’t enjoy a reputation for eccentric taste in earrings!
- Vicks VapoRub (or generic equivalent): applying it daily to fungal toenails may improve or clear mild onychomycosis over several months thanks to thymol and menthol’s antifungal properties.
- Waxed dental floss: gently place under an ingrown toenail edge to lift it and prevent it from digging into your skin.
Writer’s anecdote: everyone has always been alarmed when I’ve occasionally superglued myself back together, but now I feel vindicated by a dermatologist saying to do it!
For more on all of this, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like:
The Cult Classic Skincare Products That Have Stood The Test Of Time (And Why)
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The Best Daily Practice To Stop Falls
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Actually more important than just standing on one leg:
Where it matters the most
The older we get, the more likely we are to fall, statistically. And if you think that only happens to other/older people, just know, it will probably happen to you too, so best not be caught off-guard.
However, what do most people fall while doing? Hint: it’s not usually while perched on a post in the yoga tree position. So why are so many balance exercises aimed at staying upright in positions we do not often adopt?
Instead, most people fall while doing one or more of the following:
- walking
- reaching for something
- trying to move out of the way of something
So, single-leg standing trains balance in one position, but real falls usually happen during movement.
For this reason, the key idea today is: practicing controlled loss of balance teaches your body to either bring your center of gravity back or step quickly to prevent a fall.
The exercise: stand with your feet hip-width apart, shift your weight fully onto one foot, reach your hand sideways as far as you safely can, then return to the center. In other words, when your balance is challenged, you either pull your weight back to the center or take a quick small step with a foot to stop yourself, both of which are realistic fall-prevention responses, and good things to train.
That said, we wouldn’t want you to injure yourself while practising, so to start with at the very least, it can be best to do it in a corner (so you have two walls for emergency support).
For more on all of this plus visual demonstrations, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like:
Fall Special ← this is about how to not fall, and how to make it less likely you’ll be injured by a fall if you do
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What Your Eyes Say About Your Health (If You Have A Mirror, You Can Do This Now!)
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In an age when doctors are increasingly pressed to get you out of their office quickly and not take the time to do thorough tests, having a good basic knowledge of signs and symptoms of disease has become more important than ever for all of us:
The eyes have it:
Dr. Siobhan Deshauer is back, this time working with Dr. Maria Howard, a Canadian optometrist, who advised behind-the-scenes to ensure the best information about these signs and symptoms and what they tell us:
- Color blindness test: Ishihara color test identifies color blindness; in the version in the video, seeing “74” is normal, “12” indicates red-green color blindness, and no numbers suggest complete color blindness due to genetics or retinal/optic nerve issues.
- Yellow sclera (scleral icterus): yellow sclera indicates high bilirubin from excessive red blood cell breakdown, liver damage, bile duct blockage, or Gilbert syndrome.
- Blue sclera: indicates thin collagen in the sclera, which can be linked to osteogenesis imperfecta, Ehlers-Danlos syndrome, and Marfan syndrome.
- Pink eye: caused by infections, autoimmune diseases, or trauma; persistent symptoms or associated pain/vision changes need medical evaluation.
- Physiologic diplopia (double vision): normal test where fingers appear doubled when focusing on different planes; absence may indicate amblyopia.
- Pinhole test (visual acuity): looking through a small pinhole can determine if glasses are needed for clearer vision.
- Nearsighted vs farsighted: nearsightedness risks retinal tears and night vision issues, while farsightedness increases the risk of glaucoma.
- Eye color and health: brown eyes lower cancer risk but higher cataract risk; light eyes higher cancer risk but lower cataract risk; sudden changes may indicate a condition.
- Kayser-Fleischer rings: golden-brown rings around the iris suggest copper buildup from Wilson disease, treatable with chelation therapy.
- Corneal arcus: gray/white ring around the iris indicates cholesterol buildup, normal with aging but concerning in younger individuals, signaling hypercholesterolemia or artery narrowing.
- Limbal rings: dark rings around the iris are generally aesthetic and not health-related.
- Red desaturation test: a difference in red color perception between eyes may indicate optic nerve or retinal issues.
- Eye twitching: often linked to stress, sleep deprivation, or caffeine; persistent twitching or muscle involvement requires medical attention.
- Pupillary reflex: pupil constriction in light; abnormal responses suggest trauma, overdose, or poisoning.
- Cataracts: lens cloudiness due to age, UV exposure, smoking, diabetes, or prednisone; also occurs sometimes in youth due to conditions like diabetes.
- Yellow spots (pinguecula and pterygium): sun damage, wind, and dust exposure cause yellow spots; protect with sunglasses to prevent progression impacting vision.
- Dark spots in the eye: includes freckles, moles (nevi), and melanoma; changes require medical evaluation.
- Hypnotic induction profile: eye roll test assesses susceptibility to hypnosis.
- Floaters: normal clumps in the eye; sudden increases, flashes, or curtain-like effects may signal retinal detachment.
- Retinal detachment: caused by aging-related vitreous shrinkage; treated with lasers, gas bubbles, or retinal buckles.
- Macular degeneration (Amsler grid test): wavy, fuzzy lines or missing vision spots may indicate this condition.
- Giant cell arteritis: no, that’s not a typo: rather it is about blood vessel inflammation that can cause blindness; treated with prednisone, symptoms include headaches and vision changes.
- Near point of convergence: focus test to detect convergence issues common with excessive screen time.
- Blepharitis: eyelid inflammation causing itchiness, burning, or flaky skin; treated with hygiene, antibiotics, or tea tree oil.
- Proptosis (Graves’ disease): bulging eyes due to hyperthyroidism; treatable with medications, radiation, or surgery.
- Ptosis (droopy eyelids): indicates myasthenia gravis, temporarily improved with the ice pack test.
- Night vision issues: caused by retinal problems or high myopia, not typically vitamin A deficiency in developed countries.
- Dry eyes: caused by screen time, smoking, medications, or autoimmune diseases; managed with lubricating drops, reduced screen time, and adjustments.
- Watery eyes: caused by irritation or blocked tear ducts; treated with lubricating drops or surgery.
- Retinoblastoma: rare childhood cancer detectable through flash photography showing one white pupil; early detection enables treatment.
For more on all of these plus visual demonstrations, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like:
What Your Hands Can Tell You About Your Health
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Get Past Executive Dysfunction
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In mathematics, there is a thing called the “travelling salesman problem”, and it is hard. Not just subjectively; it is classified in mathematical terms as an “NP-hard problem”, wherein NP stands for “nondeterministic polynomial”.
The problem is: a travelling salesman must visit a certain list of cities, order undetermined, by the shortest possible route that visits them all.
To work out what the shortest route is involves either very advanced mathematics, or else solving it by brute force, which means measuring every possible combination order (which number gets exponentially larger very quickly after the first few cities) and then selecting the shortest.
Why are we telling you this?
Executive dysfunction’s analysis paralysis
Executive dysfunction is the state of knowing you have things to do, wanting to do them, intending to do them, and then simply not doing them.
Colloquially, this can be called “analysis paralysis” and is considered a problem of planning and organizing, as much as it is a problem of initiating tasks.
Let’s give a simple example:
You wake up in the morning, and you need to go to the bathroom. But the bathroom will be cold, so you’ll want to get dressed first. However, it will be uncomfortable to get dressed while you still need to use the bathroom, so you contemplate doing that first. Those two items are already a closed loop now. You’re thirsty, so you want to have a drink, but the bathroom is calling to you. Sitting up, it’s colder than under the covers, so you think about getting dressed. Maybe you should have just a sip of water first. What else do you need to do today anyway? You grab your phone to check, drink untouched, clothes unselected, bathroom unvisited.
That was a simple example; now apply that to other parts of your day that have much more complex planning possible.
This is like the travelling salesman problem, except that now, some things are better if done before or after certain other things. Sometimes, possibly, they are outright required to be done before or after certain other things.
So you have four options:
- Solve the problem of your travelling-salesman-like tasklist using advanced mathematics (good luck if you don’t have advanced mathematics)
- Solve the problem by brute force, calculating all possible variations and selecting the shortest (good luck getting that done the same day)
- Go with a gut feeling and stick to it (people without executive dysfunction do this)
- Go towards the nearest item, notice another item on the way, go towards that, notice a different item on the way there, and another one, get stuck for a while choosing between those two, head towards one, notice another one, and so on until you’ve done a very long scenic curly route that has narrowly missed all of your targetted items (this is the executive dysfunction approach).
So instead, just pick one, do it, pick another one, do it, and so forth.
That may seem “easier said than done”, but there are tools available…
Task zero
We’ve mentioned this before in the little section at the top of our daily newsletter that we often use for tips.
One of the problems that leads to executive function is a shortage of “working memory”, like the RAM of a computer, so it’s easy to get overwhelmed with lists of things to do.
So instead, hold only two items in your mind:
- Task zero: the thing you are doing right now
- Task one: the thing you plan to do next
When you’ve completed task zero, move on to task one, renaming it task zero, and select a new task one.
With this approach, you will never:
- Think “what did I come into this room for?”
- Get distracted by alluring side-quests
Do not get corrupted by the cursed artefact
In fantasy, and occasionally science fiction, there is a trope: an item that people are drawn towards, but which corrupts them, changes their motivations and behaviors for the worse, as well as making them resistant to giving the item up.
An archetypal example of this would be the One Ring from The Lord of the Rings.
It’s easy to read/watch and think “well I would simply not be corrupted by the cursed artefact”.
And then pick up one’s phone to open the same three apps in a cycle for the next 40 minutes.
This is because technology that is designed to be addictive hijacks our dopamine processing, and takes advantage of executive dysfunction, while worsening it.
There are some ways to mitigate this:
Rebalancing Dopamine (Without “Dopamine Fasting”)
…but one way to avoid it entirely is to mentally narrate your choices. It’s a lot harder to make bad choices with an internal narrator going:
- “She picked up her phone absent-mindedly, certain that this time it really would be only a few seconds”
- “She picked up her phone for the eleventy-third time”
- “Despite her plan to put her shoes on, she headed instead for the kitchen”
This method also helps against other bad choices aside from those pertaining to executive dysfunction, too:
- “Abandoning her plan to eat healthily, she lingered in the confectionary aisle, scanning the shelves for sugary treats”
- “Monday morning will be the best time to start my new exercise regime”, she thought, for the 35th week so far this year
Get pharmaceutical or nutraceutical help
While it’s not for everyone, many people with executive dysfunction benefit from ADHD meds. However, they have their pros and cons (perhaps we’ll do a run-down one of these days).
There are also gentler options that can significantly ameliorate executive dysfunction, for example:
Bacopa Monnieri: A Well-Evidenced Cognitive Enhancer For Focus & More
Enjoy!
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The Neuroscience of You – by Dr. Chantel Prat
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The insides of people are rarely so standardized as one finds in a medical textbook, and that’s just as true of the brain as it is of any other organ—and often more so.
Our brains all look quite different from each other’s. Of course there are similarities; a wobbly mass of white and grey matter with tiny blood vessels running through. The constituent parts are (usually!) all present and correct. But… what is “correct”?
Dr. Chantel Prat takes us on a tour of the anatomical features that we may have grown or shrunken over the course of our life, according to how we’ve used them, or not. She also looks at what’s going on when it comes to the smaller scale—from the neuronal to the neurochemical.
We learn the truth (and myth) when it comes to left- and right-brainedness, and we learn how whether we saw that dress as black and blue or white and gold, depends on our circadian rhythm (and thus whether we have wired ourselves for perceiving colors more or less often under daylight or artificial light). And lots more.
The style throughout is very accessible, for a book that goes beyond most “how the brain works” books.
Bottom line: if you’re interested in the workings of your brain (as opposed to: a standardized Platonic ideal of what a brain might be), then this book will set you on the right track.
Click here to check out The Neuroscience of You, and learn more about what makes you you!
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