Why Sleep Is Important for People of All Ages

You might have heard the saying ‘the older you get, the less sleep you need’. And maybe you’ve noticed that you sleep less than you did as a young adult.

Let’s be clear, though: all adult humans need 7 to 9 hours of quality sleep per night. When we get fewer than 7 hours, it affects every aspect of our lives – how we think, how we move, how our bodies work, and even how much we enjoy spending time with others.

And older people are no exception. There are reasons some people over 60 struggle with sleep – which we’ll talk about at the end of this article – but that doesn’t mean they need less sleep.

Sleep is as essential to our health and wellbeing as air and water. If you’re someone who views sleep as optional or something you’ll fit in when you have time, read this article. Then read it again. Then share it with your friends and family. Good sleep is that important.

Sleep and Physical Health

No-one knows exactly why we need sleep. But every living organism – including some bacteria – alternates between wakeful and sleep-like states.

One reason could be that sleep lets our bodies repair our cells [1]. Our cells are constantly exposed to damage from oxidation, and sleep could give us a chance to repair that damage by conserving energy. A 2014 study, for example, found that 10 days of sleep deprivation massively increased DNA damage in rats [2].

In some ways, the exact reason doesn’t matter. Many, many studies have shown that sleep deprivation impacts everything from lung function to diabetes risk [3, 4]. There isn’t a single part of your body that isn’t negatively affected by lack of sleep.

In fact, sleep is so critical that total deprivation causes death. For example, one rodent study found that keeping mice awake for 92 hours over 4 days led to most of the mice dying from severe inflammation [5]. In humans, FFI (a rare, hereditary and incurable disease that disturbs and eventually prevents sleep) is fatal within 18 months [6].

Sleep, Heart Disease, and Blood Pressure

Sleep helps bring us back to baseline. One way it does that is by reducing sympathetic nervous system activity – our ‘flight-or-fight’ system that controls things like heart rate and blood pressure. 

Not getting enough sleep and not getting good-quality sleep can both cause our blood pressure to rise [7, 8]. When we’re tired, we’re also more likely to eat salty foods that can contribute to hypertension [7]. (We’ll talk more about how that happens in the next section.)

Many studies have also shown that lack of quality sleep significantly increases our risk of heart disease and strokes [9, 10].

Sleep and Weight Gain

When we’re sleep-deprived, we put on weight. How much we eat, what we choose to eat, when we eat, and how our bodies process that food – each one is controlled by our hormones, and our hormones are heavily regulated by our sleep (specifically, slow-wave sleep).

The two big players are ghrelin (the hunger hormone that encourages us to eat) and leptin (the satiety hormone that tells us to stop eating). Even partial sleep deprivation can lead to increased levels of ghrelin and lower levels of leptin, encouraging us to eat more [11]. Another hormone, raptin, which inhibits appetite and helps prevent obesity, is produced during sleep. Disrupted or insufficient sleep leads to less raptin and more weight gain [12].

Sleeping less can also lead us to make unhealthier food choices. Many studies have shown that sleep-deprived people opt for ‘unhealthy’, high-calorie foods over ‘healthy’, low-calorie choices [13]. Lack of sleep also affects impulse control – we don’t have the self-control to avoid sugary, fatty snacks and treats [13].

Our hormones aren’t the only cause of weight gain, either. Being tired encourages our bodies to conserve energy by moving less. It also changes when we feel like eating – sleep-deprived people are more likely to eat later in the day, which has been proven to increase weight gain [14, 15].

Sleep and Immune Systems

Why do we feel like sleeping more when we’re sick? It’s simple: sleep helps our bodies fight off infection.

The relationship between our immune systems and sleep is complex. Sleep is essential for the production and function of various immune cells – which combat everything from the common cold to cancer [16]. Lack of sleep causes your body to over-produce certain kinds of immune cells, leading to chronic inflammation [16].

That means sleep deprivation is doubly dangerous: your body will struggle to fight off infections and, at the same time, suffer attacks by its own immune cells.

Sleep and Diabetes

The evidence is clear: if you sleep less, you have a greater risk of diabetes. We now know that not getting enough sleep leads to both weight gain and chronic inflammation, but it can also impact diabetes more directly.

Even a few days of reduced sleep can reduce your glucose tolerance and insulin sensitivity [17]. Over time, that can cause diabetes to develop – or make an existing diabetes diagnosis worse. One large-scale study over 20 years found that people who slept less than 7 hours a night were 1.3 to 1.7 times more likely to develop diabetes [18].

But the relationship isn’t one way. Diabetic neuropathy, restless legs syndrome, and lower-limb swelling can all contribute to less restful nights, leading to a vicious cycle of ill health.

Sleep and Brain Health

You’ve probably heard of brain fog, the catch-all term for difficulty thinking clearly, remembering things, and making decisions. Often, it’s caused by poor sleep.

In the days following a restless night, you’ll struggle to remember things – especially things you learned the day you failed to get good sleep. REM and slow-wave sleep both play roles in:

• freeing up brain capacity before learning
• consolidating newly made memories
• filtering memories during waking hours [19].

And, if you think that only applies to information, think again. Memory-based skills (like riding a bike) are just as heavily affected.

Lack of sleep also impacts how we make decisions. Less prefrontal cortex function means sleep-deprived people have fewer inhibitions – and more difficulty making judgement calls [20, 21]. They also struggle with attention and alertness, which can affect things like response times when driving [21].   

But sleep doesn’t just help you live better when you’re awake. It actually keeps your brain healthy. According to the glymphatic system hypothesis, sleep is responsible for clearing toxic waste products from your brain [22]. Those waste products include proteins like β-amyloid, α-synuclein, and tau, all of which are linked to neurodegenerative diseases like Alzheimer’s [22].

Sleep and Mental Health

When we’re tired, we’re more easily irritated and less patient. That’s probably not surprising.

But sleep affects much more than just emotional regulation. Emotional intelligence, emotional memory, the types of emotions we feel, and even our ability to recognise emotions in others are all impacted by lack of sleep [24].

For example, we’re more likely to see the world negatively when we’re tired [24]. That includes misinterpreting things like a positive expression or tone of voice as threatening, cold or aggressive. We’re also more likely to mistrust others and swing quickly between moods [24].

Those impacts extend to mental health conditions. People who aren’t getting enough sleep are much more likely to have diagnosable depression and anxiety disorders, as well as severe mental health conditions like bipolar disorder and schizophrenia [21, 24, 25, 26].

Our mental health is no different to our physical health: good sleep is essential for both.

How Much Sleep Do We Need?

Almost every adult, no matter how old, needs at least 7 hours of sleep per night [27]. Getting fewer than 7 hours a night for 3 months or more is a diagnosable condition [27]. Even if you feel like you can get by on less, you can’t – you’re just so used to chronic sleep deprivation that you don’t remember what being fully rested feels like.

Why Do Older People Sleep Less?

If you’re reading this as someone past their 20s, you’ve probably noticed that your sleep has gotten worse and worse over the years. That’s not your imagination. Over your lifespan, your non-REM sleep will probably keep decreasing in both quantity and quality [29].

Exactly why isn’t clear. One cause could be changes to our circadian rhythms. Older adults have weaker circadian rhythms; the timing of those rhythms also moves forward, which can put them at risk of ‘social jet lag’ (being kept up by social commitments when their bodies want to sleep) [30].   

Various sleep-affecting hormones, like growth hormone and testosterone, also decrease as we get older [30]. That includes melatonin, the so-called ‘sleep hormone’ that regulates our circadian rhythms [30, 31].

Finally, ageing increases our risk of health conditions that disrupt our sleep – which we often manage with sleep-stealing medications [walker]. That includes things like weakened bladder muscles, which can lead to us waking up more often to use the bathroom [29]. 

How Can I Improve My Sleep?

Hopefully, this article has convinced you: sleep is incredibly important. Now, you’re probably wondering what you can do to get the deep, satisfying rest your body needs.

Try starting with these 10 sleep hygiene steps:

1. Make sleep your priority. If you do one thing each day, make it a good sleep.
2. Go to bed and wake up within +/- 30 minutes of the same time each day.
3. Go outside and get direct sunlight (no sunglasses) within 30 minutes of waking up. If you can’t, use a SAD lamp instead.
4. Create a sleep sanctuary. That means investing in a high-quality sleep surface in a cool, dark, distraction-free space.
5. Avoid bright lights (especially screens) at least 1.5 hours before bed.
6. Have a sleep routine. Set aside an hour to relax and unwind (without screens) before bed.
7. Avoid heavy meals, alcohol, and exercise at least 2 hours before bed.
8. Avoid caffeine and naps at least 6 hours before bed.
9. Ask your doctor about the sleep impacts of any medication.
10. Don’t lie in bed awake. If you can’t sleep for 20 minutes or more, get up and do a relaxing activity until you feel sleepy.

Keep in mind that those 10 steps are just a starting point. Everyone’s sleep challenges are different. It might take time for you to find the right lifestyle and behaviour changes. The main thing is that you keep trying – because there is almost nothing more essential for your health than good sleep.