"People under 27 are more likely to be night owls, which can be a problem when they enter the workplace," adds James Wilson, a sleep behaviour expert who has worked with the Royal Society for Public Health.
"Simply going to bed earlier won't help - don't force yourself to be in bed by 10 or 11. Instead, focus on quality over quantity and on establishing a wind-down routine at least an hour before you would ideally want to fall asleep.
"And if you're watching TV before bed, make it funny or trashy, rather than something with a cliff-hanger, so your brain can start to switch off."
30s
"This is when work, financial stress and raising a family all kick in," says Neil Stanley.
If you're lying awake, brain whirring, Wilson and Stanley both say the key thing – rather than attempting any particular exercise or counting sheep (which Oxford University has officially debunked for its sleep-inducing abilities) – is to stop actively trying to sleep, as this will only make matters worse.
"Avoid getting into that mindset of counting how many hours you've got left before you need to be up, worrying about how tired you'll be," says James Wilson. "Instead, try thinking about a time you had little or no sleep, but managed to perform fine. Reassure yourself that you've coped before, and you're much more likely to calm your brain so sleep can happen."
For women in their 30s, pregnancy can bring insomnia, and waking throughout the night.
As many as one in four pregnant women are affected by restless legs syndrome, says Dr Leschziner. As the name suggests, this neurological disorder causes an uncontrollable urge to move the legs, or sometimes an itching, tingling, burning or creepy-crawly sensation. It tends to be worse in the evening, stopping people falling asleep, but it can also cause involuntary movements that wake people up.
"Low iron is a common trigger and supplements can treat it," says Dr Leschziner. "So if you're pregnant - or if you have particularly heavy periods - it is very much worth asking your GP to check."
Of course, the broken nights really begin when baby arrives. In fact, parents suffer disturbed nights for six years afterwards, according to research published this year by the University of Warwick.
And a disturbed night's sleep leaves you feeling as bad as an extremely short one - a 2014 study by Tel Aviv University found that women who slept for eight hours, but were woken four times, were as groggy and tired as women who'd slept for just four hours.
"Once a child gets past feeding, my advice is to take turns on night time duties rather than splitting them in the same night," says Neil Stanley. "If you can, agree in advance who's going to get up if a child wakes, while the other person sleeps through - with ear plugs in if needs be - and take turns that way."
40s
Heavy snoring caused by sleep apnoea is common as people hit midlife, says Dr Leschziner. Sleep apnoea is where the soft tissues in the throat collapse during sleep, temporarily – but often repeatedly – obstructing breathing, disturbing sleep, although you may not remember in the morning. It's associated with being overweight, and particularly with weight around the abdomen and neck.
"If you're snoring, feeling tired in the day, or waking yourself up choking or gasping this could point to sleep apnoea," says Dr Leschziner. "The first thing to try is weight loss, as that often improves it."
It can also be treated with a continuous positive airway pressure (CPAP) device – a small pump and breathing mask to keep the airway open.
As children start to fly the nest, leaving you with a spare bedroom, Stanley suggests this may be a good age to consider a 'sleep divorce': separate beds, or even bedrooms.
"It's got nothing to do with the strength of your relationship," he says. "It's just pragmatic. We know from research that the majority of sleep disturbance is down to your bed partner, whether it's physical movement or the noises they make."
50s
Women going through the menopause between the ages of 40 and 59 are more likely than both post- and pre-menopausal women to sleep for less than seven hours a night, according to a US research.
"Hot flushes are likely to be the biggest problem, as to fall asleep you need to lose one degree of body heat," explains Neil Stanley. "So avoid doing anything that raises body temperature at night: wear cotton pyjamas, don't eat late or drink alcohol or exercise in the evening."
Sleep practitioner James Wilson adds: "People in midlife are often sold memory foam mattresses on the basis that they're better for aches and pains, but memory foam is not great for temperature regulation. You'd be better off with one with more breathable, natural fillings. Likewise, look for a duvet made with bamboo or alpaca fleece."
For both men and women, it's common for sleep to be disturbed at this age because you need to get up to go to the loo. "Getting up once in the night is perfectly natural," says Stanley.
"But more than that is a problem. Far too many people think, 'Well, I'm old, what do I expect?', but this could be down to something more severe (a prostate issue, for example) so you really need to see your GP."
He advises avoiding alcohol, which stimulates the bladder, in the evening, and making going to the loo the last thing you do before you switch off the light. "Obviously, avoid drinking large amounts of fluid before bed, but make sure you have water to sip to avoid getting dehydrated as, conversely, that can also wake you up."
60s
It's a myth that we need less sleep as we age, according to Dr Leschziner. "The reality is that they probably need just as much as younger adults, but they're less good at achieving it," he says.
"An important one to watch out for at this age is REM sleep behavior disorders, which tends to be something we see in older men," says Dr Leschziner. This is where people start to act out their dreams at night (during REM or rapid-eye movement sleep, where normally the brain would keep us paralysed).
"Often this can have a violent component, with people thrashing around and kicking their legs, risking injuring themselves and their partners," he says. These are distinct from sleepwalking or night terrors (which occur in the deeper, non-dreaming stages of sleep) and tend to occur in the latter half of the night, because that's when we have most of our REM sleep.
"People mustn't just live with this, but should seek medical help," says Dr Leschziner. "It can be treated with medication. We also know that it can sometimes be a precursor to other neurological disorders, including Parkinson's and Lewy body dementia, showing up years before other symptoms."
James Wilson says retirement can also trigger sleep problems. "For a lot of people, their job gives them their clock and without that daily routine, sleep can suffer," he says, adding that you might actually need to be more strict about your habits now.
"Things you might have done when you were working – whether it was watching the news right before bed, drinking alcohol or a coffee late in the day – without consequence might start to be more of a problem because you're no longer as physically and mentally tired.
"Getting into the habit of late nights and lie-ins because you don't have to get up for work, can also confuse the body clock – our bodies like consistency," he adds.
Drugs for age-related problems – such as pain medication and PPIs for acid reflux - can also interfere with sleep, adds Neil Stanley: "Have a conversation with your GP or consultant if you're on medication and not sleeping well, as there may be alternatives."
70s and beyond
"Unfortunately, insomnia in this age group is very, very common," says Dr Leschziner. "That's because as we get older the brain is less good at maintaining sleep.
We also spend less time in REM or dreaming sleep, says Stanley. "In essence, you get less of the more restorative sleep. This means even if you get the same amount of sleep you always have, you're unlikely to feel as refreshed as you did in your 20s."
That doesn't mean you should put up with very poor sleep.
"Cognitive Behavioural Therapy for Insomnia – known as CBTi – is highly effective and should be the first-line treatment, rather than drugs because it's more likely to induce a normal pattern of sleep, whereas the drugs just sedate you," says Dr Leschziner. "It works in the majority of cases and is available on the NHS."
CBTi involves working with a therapist to change attitudes to sleep, often in conjunction with a strict sleeping routine (naps may be prohibited, for example).
There are also online programmes you can access on the NHS. "These are almost as effective as seeing someone in person," adds Dr Leschziner. (Go to www.sleepstation.org.uk for more information).
Another common problem is wanting to get up and go to bed very early, he says. "This is a normal shift in our body clock that seems to happen over 70, but it can become extreme, meaning someone is waking up at 3am."
Spending a lot of time indoors may also exacerbate this natural shift, as daylight is key to keeping our internal clock in sync with the 24-hour day.
"So increasing your exposure to natural light in the afternoon and early evening may help, as getting more daylight at this time of day delays the onset of melatonin, which makes us feel sleepy."
A specialist may also prescribe a synthetic version of the sleep hormone melatonin to shift the clock.
"My main advice is don't assume that poor sleep is just part of the ageing process," adds Dr Leschziner.
"If you are regularly unable to stay awake in the day, this could possibly be part of a sleep disorder or another underlying issue – never assume there's nothing that can be done."
