Sleep deprivation is harmful to your health

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Puffy eyes, lack of energy and grogginess are the least of your sleep problems. Getting less than six hours of sleep a night is detrimental to your health, writes sleep expert Jane Wrigglesworth.

Did you know? One in three people have a sleep problem

While you might think your six-hours-a-night sleep habit is nothing to worry about, studies reveal that chronic sleep deprivation can be a ticking time bomb. Sleep loss is linked to an array of catastrophic health issues, including heart disease, hypertension, diabetes, depression, low immunity and weight gain, among other diseases and disorders. If you’re consistently getting less than 6 hours of sleep a night, studies show you’re:

  • 50% more likely to suffer a heart attack
  • 56% more likely to suffer high blood pressure
  • 60% more likely to develop breast cancer
  • 4 times more likely to suffer a stroke

There’s been talk on the news lately too that lack of sleep can lead to Alzheimer’s disease. That’s because when we’re sleeping, the glymphatic system (the brain’s very own waste disposal system, similar to the lymphatic system) is 10 times more active than when we’re awake. Just like every other organ, our brain produces waste throughout the day. These wastes – dead cells, toxins and other nasties – are flushed out during sleep. If we’re not sleeping, they’re not going anywhere, and harmful waste products like amyloid protein, which is linked to Alzheimer’s disease, remain behind. If we don’t get quality sleep at night, the glymphatic system cannot do its job.

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Not only that, our waistlines are also affected by lack of sleep. When you’re sleep deprived, leptin (the hormone that signals satiety) falls, while ghrelin (the hunger-stimulating hormone) rises. This leads to your body craving junk food for a quick burst of energy to stay awake. A study by the Mayo Clinic found you’re:

  • 23% more likely to be overweight when getting only 6 hours of sleep a night
  • 73% more likely to be overweight when it drops down to 4 hours

Breast cancer

Women who sleep less than six hours a night could be raising their risk of breast cancer by more than 60%, according to research. “Evidence is accumulating that light at night, and the consequent decrease in melatonin, may be a major driver of breast cancer,” says cancer epidemiologist Dr Richard Stevens. Melatonin has powerful antioxidant, anti-inflammatory and immune properties, and it inhibits the proliferation of a wide range of cancer cell types, as well as triggering cancer cell apoptosis (self-destruction). “Night-time melatonin is a relevant anticancer signal to human breast cancers – 90% of human breast cancers have specific receptors for this signal,” says Dr Stevens. This is thought to explain why nurses who regularly work night shifts have high rates of breast and colon cancer. Studies also found that post-menopausal women who slept poorly had a higher likelihood of cancer recurrence (cancer returning).

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How light affects melatonin levels

Light stimulates alertness. That’s a good thing first thing in the morning, but during the evening it can cause sleep disruption. When darkness descends at the end of the day, the light sensitive cells in our retinas signal our brains that it’s time to prepare for sleep. The pineal gland switches “on” and begins producing melatonin (aka the sleep hormone), which regulates our sleep-wake cycle, slowing metabolic functions and lowering body temperature. This, in turn, makes us sleepy and less alert. Melatonin levels continue to rise throughout the night and stay elevated until the sun rises, when your pineal gland switches “off”. However, exposure to bright light throughout the evening inhibits the natural production of melatonin, which can interfere with the sleep-wake cycle, and consequently the quantity and quality of sleep. Managing your exposure to light in the evening is critical to ensuring the natural sleep-wake cycle functions as it should. The last thing many of us do before bedtime is stand in front of a bright light to brush our teeth. Or we check our emails or social media sites one last time (more on that below). To prevent stimulation, dim the lights a full hour before bedtime. Use a dimmer switch to control brightness, or install low wattage bulbs in table lamps. You might also consider installing a flexi bulb, like Philips’ Scene Switch bulb, which can be switched from a cool light for daytime and a warm relaxing light for evenings. No special equipment or switches are needed. You simply insert the bulb into your existing light fitting. When going to sleep, block out all light in your bedroom (blackout curtains are ideal for this). Install a red nightlight if necessary – outside your bedroom. Turning on a light in the middle of the night to go to the bathroom will disrupt your melatonin production. Did you know? Lux levels for pre-bedtime activities, like reading or listening to music, should be less than 180 lux. A typically lit home may have lux readings in the range of 300-500. Lux outputs are determined by the intensity and colour of your lights. To work out watts to lux, check out this calculator here.

Beware of blue light

Computers, tablets, mobiles and TVs all emit a bright blue light, and it’s this light that the light-sensitive cells of our retinas are most sensitive to. This short wavelength blue light suppresses the production of melatonin (red light has the least power to interrupt circadian rhythm and suppress melatonin), which throws our body’s biological clock (the circadian rhythm) out of whack. Incidentally, today’s energy-saving light bulbs, including LED lights and compact fluorescents, produce more blue light than the traditional incandescent light bulbs. Switch off your computers, mobile phones and television AT LEAST an hour before bedtime, and leave them out of the bedroom. If you check your mobile in the middle of the night, the light your eyes register is as good as telling your brain, ‘Wake up! It’s daytime!’ The same goes for luminous alarm clocks.

Brain fog and memory loss

A full sleep cycle (1.5-2 hours) consists of Rapid Eye Movement (REM) and NREM (Non REM). For the average adult, NREM makes up 75% of sleep time while REM makes up 20-25%. Typically, REM sleep happens about 90 minutes after you fall asleep. The brain is very active during REM. In the first period of sleep, REM typically lasts around 10 minutes. As the night progresses, the time spent in REM gets longer. Therefore, the longer you sleep, the more you experience REM sleep. This is important for several reasons, but one significant reason is that it allows for the day’s activities to be adequately processed by the brain. It’s essential for forming and consolidating memories, particularly of procedural and spatial memory. Studies have shown that people spend more time in REM sleep following days they’ve been involved in the learning of new tasks. This is why those who are sleep deprived will often talk of a ‘foggy brain’ and reduced memory. We are more likely to wake from REM sleep than from NREM sleep, though these are usually micro-awakenings of just a few seconds only. Because these awakenings are so short, we don’t usually remember them. However, if your brain is over-stimulated, as experienced through caffeine consumption (see below), you can wake up fully, and it may take the length of an entire sleep cycle to get back to sleep.


When sleep is poor, people often reach for a shot of caffeine (coffee, tea, cola, energy drinks, chocolate, etc) – a quick energy-producing food. As a stimulant, caffeine is often used to increase alertness. It works by blocking the actions of the sleep-inducing chemical adenosine, which our bodies naturally produce throughout the day. When awake, the levels of adenosine in the brain rise each hour. High levels of adenosine lead to sleepiness, and by the end of the day a natural build-up of adenosine generates a desire to sleep. During sleep the body breaks down this excess adenosine, which makes a person more alert after a good night’s rest. However, as caffeine blocks adenosine’s actions in the brain and increases alertness, this can lead to prolonged sleep latency (the time it takes to get to sleep), increases in light sleep and shortening of deep sleep time, more frequent awakenings and shorter total sleep time. As caffeine has a half-life of six hours, after consuming it you will still have half the caffeine in your body six hours later. The later in the day you consume caffeine, the more your sleep will be affected. The irony here is that people often use caffeine as a way to improve alertness after a bad night’s sleep. Have it in the morning, but avoid it completely in the afternoon. When you sleep well, you won’t need the caffeine to keep yourself awake during the day.

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How’s YOUR sleep?

Are you getting enough ZZZ’s? If sleep is something that you’ve been struggling with, I invite you to click on the button below to set up a complimentary sleep strategy session with me. Seriously! It’s free. Let’s see if we can get you sleeping again.

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Jane Wrigglesworth is a Sleep Coach for How to Sleep Well. She works with adults who have difficulty sleeping.

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