Light Sleeper Leanne

Notes from 5-day challenge, July 2020

Day 1 - Light and the circadian rhythm


There is a growing body of evidence that disrupted or insufficient sleep is, quite literally, a killer. And children are particularly vulnerable as this critical sleep-wake cycle is forming in the first years of life. Every living creature under the sun from plankton to polar bears evolved to sense shifts in daylight – from morning to night and summer to winter. These differences let us know when it is safe to for forage for food, when to move or migrate and when when to hide and hibernate.

Studies of the longer-term impact of poor sleep on pre-school children make sobering reading. For example, three to five year-olds who get an average of one hour per night more sleep carry an average of 0.39 kilos less weight aged seven - or 0.4 points lower BMI. Equally, getting one hour less sleep between three to five years of age increases the risk of obesity by 56% by the time they reach seven.

Studies also show that kids with poor sleep patterns are eight times more likely to suffer the emotional problems that lead directly to depression and ADHD type symptoms. One hour below the mean sleep duration in pre-school children increases the odds reported by parents of overactivity by 1.30, anger + 1.40, aggression +1.81, impulsivity +1.44, tantrums +1.46 and annoying behaviors by +1.40.

How the sleep-wake cycle works

Light signals are received by the SCN, or the ‘master clock’ in the brain. The steady shift from blue ‘wake up’ morning into warm ‘wind down’ evening light is the single most reliable indication of seasonal and daily cycles. Relying on temperature may seem a more obvious solution but a heat wave or a cold snap could easily catch us off-guard.

These cues cascade to entrain the responses of every single pathway and organ in the body, from the adrenal system, the heart to the pancreas, the guts to the muscles. This system takes shape from the first days of gestation – and continues through to adolescence and beyond. But those early years are vital to our long-term health.

We evolved to thrive in these natural conditions, not the artificial screens and LED’s that fill our homes. If you compare the wavelengths of morning sunlight and those given off by screens and cool white LED’s, you will see a peak in the same ‘wake up’ blue end of the spectrum. The warm white LED spectrum is closer to an evening pattern, which will allow the body’s natural ‘switch off’ process to begin. And it does not take much to disrupt this delicate balance.

But not all LED's are the same - a reputable brand such as TruWave by Sylvania, shown here, is designed to imitate the sun's natural spectral curve.

It doesn’t take much to mess it up

As little as five minutes in bright lights will suppress that ‘wind down’ signal – and one study showed that women who read an ‘e-book’ rather than a printed one had significantly less of the deep REM sleep than those who read a printed book – even though they slept the same number of hours. This chart shows the critical lux levels given out by different displays – around 100 lux is enough to disrupt the cycle.


Luckily, there are some simple, highly effective things you can do about it.

1. Work as a team – make the time to discuss the issues and find solutions together.

2. Switch of screens and cool LED at least one hour before bed – and take them right out of the room

3. Choose good-quality cool and warm lamps to support study, play and rest – check the specification and always buy a reputable brand

4. Use the technology that’s out there – blue filters for screens and glasses and the growing number of apps designed to help you to manage screen time and tune the lights from cool to warm white

5. Choose a place to recharge all your screens and phones together – they will follow your lead

Track your results – and give yourself gold stars for making the small changes that will change your world for good - not only now but for years to come.

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