By most reasonable estimates, modern life means about a third of New Zealanders suffer from not enough sleep or sleep deprivation.
It's an annoyance, an inconvenience which often leaves people tired, grumpy and a little unproductive, right?
It's rather more than that. This is how Professor Matthew Walker, director of the Centre for Human Sleep Science at the University of California, Berkeley, put it in an interview with the Guardian in September last year: "There is a catastrophic sleep loss epidemic [affecting the world]."
He says there are powerful links between sleep loss and, among other things, Alzheimer's disease, cancer, diabetes, obesity and poor mental health. Last year he released a book (Why We Sleep) designed to make people strive more for eight hours sleep (he counts anything under seven as sleep deprivation; other experts say six is the tipping point) because of the health risks.
These warnings can be taken to apply to New Zealanders too – because successive surveys over the past few years have consistently painted a picture of lost sleep among a large slice of the Kiwi public.
In 2015, a Southern Cross Health Society survey revealed almost a quarter of Kiwis felt tired or fatigued every day, rising to 36 per cent for under-30s.
In 2016, a Colmar Brunton survey said 60 per cent felt tired due to lack of sleep and that 36 per cent got only 4-6 hours a night. A separate survey in the same year said 35 per cent of New Zealanders were sleep deprived (especially women) and, according to the Listener, 37 per cent of 30 to 60-year-olds report never or rarely getting enough sleep across various health surveys from 1999-2008 and 2013-2014.
More than 20 large-scale epidemiological studies from around the world have revealed that the shorter you sleep, the shorter your life may be. Adults above the age of 45, who sleep less than six hours a night, are said to be more prone to multiple heart complications compared to those with 7-8 hours of sleep.
Britain's NHS says the one in three Britons suffering from poor sleep are at risk of serious medical conditions, including obesity, heart disease and diabetes, shortening life expectancy: "It's now clear that a solid night's sleep is essential for a long and healthy life."
While healthcare workers, employers and politicians in particular should pay greater attention to the benefits of sleep, Walker says people need to do so on an individual level.
"Once you know that after just one night of only four or five hours' sleep, your natural killer cells – the ones that attack the cancer cells that appear in your body every day – drop by 70 percent, or that a lack of sleep is linked to cancer of the bowel, prostate and breast, or even just that the World Health Organisation has classed any form of night-time shift work as a probable carcinogen, how could you do anything else?"
Modern life has been suspected in many new ills – sleep deprivation among them. Busy work and social lives are among the suggested causes, as is information overload, overuse of technology, and anxiety.
Walker says: "No one wants to give up time with their family or entertainment, so they give up sleep instead. Anxiety also plays a part. We're a lonelier, more depressed society."
In New Zealand, there are no studies delving deeply into sleep habits from decades ago. But in Britain in 1942, less than 8 per cent of the population slept for six hours or less a night; that swelled last year to one in three.
So what keeps us up at night? Stress, alcohol, caffeine, eating late, getting home late, mental stimulation and too much screen time have all been mentioned as "sleep stealers". Walker says it has also become fashionable to show durability by operating on only a few hours' sleep – while stigmatising healthy amounts of sleep with a "label of laziness".
A national business development manager and mother of three Cathy Weck estimates she gets about 5 hours' sleep a night: "Who has time for sleep? My life is too full to fit into just 16 of the 24 hours a day."
Her high pressure job requires long hours. She has a commute of around two hours a day and, somewhere in there, Cathy fits in training for her marathons: "I'm texting or emailing in the evenings and it's not unusual for me to be vacuuming at 6am before I head off to work."
So, what to do to promote healthy sleep patterns? Southern Cross Health Society gives the following guidelines:
• Keep screens out of the bedroom.
• Cut down screen time – stay screen-free for the hour leading up to bedtime.
• Write down tasks for the following day – so you won't lose sleep worrying about what's coming up.
• Develop a pre-sleep routine – discover what works for you and stick with it.
• Manage stress levels throughout the day.
• Take up calming activities - such as meditation, mindfulness, reading, or Yoga.
• Know where to find help – sleep.org.au is a great place to start, but there are plenty of other resources to be found online.
