Millions of Kiwis work nights. They clean offices, drive taxis and trucks, care for the sick and elderly, stack shelves and deal with clients in different timezones. But there is a dark side to working the graveyard shift. A growing library of research shows nocturnal work takes a serious and permanent toll on the health of those rostered on the night shift.

Andrea Vance and Iain McGregor report from six work sites in the dead of night, and investigate how the staff are at risk.

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Maraea Hapi Crowe takes care of dementia patients through the night.

Maraea Hapi Crowe takes care of dementia patients through the night.

Maraea Hapi Crowe wakes with a start, to the sudden blare of a car horn. As her blurred vision clears, the traffic lights in front of her shift from green to red. The 69-year-old has fallen asleep, driving home from her night shift caring for dementia patients. 

“I am just so thankful that the good Lord is watching over me because there have been times I have been driving home and I’ve fallen asleep, and the cars behind me are tooting their horns,” she says. “It’s very dangerous.

Drowsy driving was implicated in 28 deaths in 2018.

Drowsy driving was implicated in 28 deaths in 2018.

“Sometimes I'm so tired when I finish work I'll go out and I'll sit in my car and [I’m asleep] within five minutes. And then I’ll wake up and think what am I still doing here? I have a nanny nap.”

It’s not a nanny nap, but a micro-sleep. These brief episodes - lasting several seconds - are extremely dangerous and regularly implicated in fatal accidents.

In 2018, 28 people died and 139 were seriously injured in 124 accidents where fatigue was at least partly to blame.

Hapi Crowe belongs to a growing army of nocturnal workers.

Healthcare workers, security guards, bakers, truck drivers, supermarket and port workers and even snow groomers are among its ranks.

That nocturnal workforce is growing, fuelled by an insatiable demand for consumer goods and services. But it is mostly invisible to those of us on the clock during daytime hours.

Globally, an estimated one in five workers is engaged in regular night shift work.

In New Zealand, the number of night shift workers has risen by 60 per cent in a decade.

A Stats NZ survey, in 2008, showed 202,200 people recorded working at least one night shift (between 11pm and 5am) in the previous four weeks. By 2012, that had increased to 236,000, and by 2018, 323,000 were working nights. 

More people (48 per cent) are also working evening shifts (7–11pm). In 2008, 661,100 recorded evening shifts, by 2012 that had risen to 712,300 and by 2018, 976,500. 

A low wage economy, high living costs and expensive childcare are among the factors driving people into night shifts, or to consider second evening jobs. 

E tū director Kirsty McCully says we don’t do enough to protect, or compensate them.

“If you're a cleaner inside an office building or a mall, or a security guard, [workers] who have low hours, low job security, low wages, it's less likely that there'll be compensation for working those hours.

“Nor is there anything else that's really done to minimise or mitigate the impacts of it. 

“There's an assumption that is the nature of the job. You know, you apply for a job and the job is in the evenings and during the weekend.”

Jared Abbott, of First Union, believes there has been an increase in the exploitation of night shift workers. He fears it will be exacerbated by a spike in unemployment following the Covid-19 pandemic.

“There are a lot of employers really focused on what they would call the business needs and the idea of having operations run 24 /7 to get maximum productivity. 

“Probably one of the most alarming responses that we get from employers, is the idea that there's always someone else who would take the job, especially with the increase in unemployment that we're seeing.

It is quite likely that employers will use that as an opportunity to further push people into these unsociable hours just to obtain work.

Jared Abbott

Working into the night is a fundamental challenge to the finely-tuned rhythms of our bodies and makes us vulnerable to disease.

Sleep is not an indulgence, but the time when our bodies carry out some basic maintenance. It also helps us process the events of our day, and create memories.

In a swathe of scientific studies, undertaken across the world, long-term night shift work has been linked to chronic illness, including an increased risk of some cancers, heart disease, gastro-intestinal problems, diabetes and obesity.

Profound sleep disruption is also linked to increased morbidity, and mental illness.

Crane operator Willie Maipi has worked night shifts on Auckland’s wharves for 18 years.

He loves his job - particularly the camaraderie with his tight-knit team - but he says it can be an unhealthy lifestyle. A few years ago, Maipi noticed he was gaining weight. 

In the middle of a house renovation, he also had trouble sleeping.

“I was at a weight of maybe 170kg and that’s through lack of sleep and I’d say not eating properly.  It does take a toll on your health. I had high blood pressure, I was on the verge of diabetes.

“I had to lose weight. I've got down to about 108kg and I felt good. So, I try and do something every morning when I get home. Walking the dogs or I was right into my boxing, I’ve got a bag out the back.”

He sticks to green tea and water. “Coffee just wires you right up. Maybe because I’ve been doing it for so long, I’ve kind of trained my body not to get tired.

“Once you start feeling like that, the night just seems to drag on, so you tend to keep yourself busy and active.”

Working after dark runs counter to the body’s circadian rhythm, an internal clock or timer that lets our glands know when to release hormones. It also controls mood, alertness, and body temperature over a 24-hour period.


Melatonin is known as the hormone of darkness, because that is when it is produced.

Suppressing natural melatonin release –  by being exposed to artificial light during the night time – can promote cancer growth.

“We do permanent damage to our DNA in our body and it is called oxidative damage,” Alexander Tups, associate professor at the Otago University’s Centre of Neuroendocrinology and Brain Health Research explains. 

“Each time we eat, we burn energy and we produce free radicals - and that leads to DNA damage in the long run. 

“One way to overcome this is by eating less - but another way is also to have regular sleep to make sure the melatonin signal is not disrupted - because what melatonin does is it clears those free radicals.

“It is a very powerful antioxidant and it is also anti-inflammatory. It helps our body to get rid of toxins - and if we continue to disrupt the cycle for years and years, toxins will accumulate and they cause DNA damage.”

Tups says this can lead to increased risk of cancer, or brain disease like Alzheimer's. 

And there is more bad news: sleep disruption can also lead to metabolic disease (which increases the risk of heart disease and strokes), diabetes and it’s likely to make you fat.

Tups published research last year which found connections between obesity, diabetes and the body clock. 

Using mice, he found repeated jetlag (a circadian rhythm sleep disorder) led to weight gain and severe diabetes symptoms. He’s now hoping for funding to continue the work.

When we work at night and are exposed to bright light, suddenly the melatonin is not produced in the night anymore.

Alexander Tups

“Then, when we try to sleep during the day - but we don’t have melatonin because it is naturally produced in the night - then we can’t sleep that well.”

It would be near impossible to reverse this circadian rhythm, Tups says. 

“The best way to cope with it is to sleep in a really dark room without light entry at all and hopefully no noise, but still have light exposure when the night shift is occurring.

“But you need to do that every day - and that is the problem here. What happens is maybe it is a rotating shift, and the next week people are not doing night shift, or during the weekend, people are active during the day and sleep during the night.”

Edwin Ikani, a foreman, found his body couldn’t handle working at night. After four years of feeling like “a zombie” he gave it up - even though the pay was much better. 

“I was working from 12 midnight to 8am in a warehouse and after the first year I started noticing the changes.

“My health suffered. I used to be really fit and the first year I was able to switch my gym routine to morning, but after six months it just got too hard. I felt I didn't have the energy. I put on a couple of pounds.

“My immune system started getting a bit weaker … coughing a little. But the main one was I started getting migraines about 2 or 3am.”

Ikani found he couldn’t catch-up on lost sleep. 

“My body didn't know how to handle that change. I’d talk to someone, like my parents, and I'd be looking at them but my mind was asleep. I couldn’t follow what they were saying.”

Ikani, 36, from Mangere, says he got his life back when he took another job. “I get good sleep, I feel energised, I get through the day and I'm so glad to be off it.

“I know you get a little bit of extra money but I think it's not worth it.”

Altered sleep patterns because of shift work are associated with irritability, depression, isolation and anxiety.

A study published in the American Journal of Public Health last year, reported that shift workers had a 30 per cent higher risk of poor mental health and depression. And those shift workers had a 70 per cent higher risk of depression compared to women rostered on day shifts.

“Sleep is fundamentally important in terms of our emotional health,” says Associate Professor Leigh Signal, of Massey University’s Sleep/Wake Centre.

Fonterra truck driver Darren Mason arrives home after a shift.

Fonterra truck driver Darren Mason arrives home after a shift.

“Originally, it was thought sleep or changes or disturbances to sleep, were symptoms of depression.

“They certainly are a diagnostic criteria of depression, but what we now know is that often disturbances to sleep actually precede or can be seen before the onset of depression.

“There's a chicken and egg thing going on, so if we muck with our sleep, we muck with our mental health and well being which in turn mucks with our sleep.”

Night shift workers must learn to prioritise shut-eye, she says. 

“It's not necessarily rocket science. Instead of going home and putting the laundry on, and [doing] six jobs around the house, the most important thing is climbing into bed.” 

Agnes Balente, 42, has worked nightfill at a Christchurch supermarket for almost a year. She’s quick and adept with her retractable box cutter, placing a box on the shelf and then slicing through the cardboard to open up the front. 

Under the harsh glare of the fluorescent lights, she and her colleagues pound the aisles, pausing occasionally to help a customer. They laugh and chat quietly, but unceasingly plug the empty gaps.

Agnes Balente, left, says night work is a sacrifice for her family's sake, but she is happy in her work.

Agnes Balente, left, says night work is a sacrifice for her family's sake, but she is happy in her work.

When she finishes at 3am, she makes the short drive home to Cranford through empty streets. Balente prepares packed lunches for the family before falling into bed. At 8am, she wakes to take her child to school, and then goes back to bed, sleeping until mid afternoon.

“I wake up at 2pm to prepare for my dinner for my husband, like that. It's everyday, routine,” she says.

Originally from the Philippines, she moved from Riyadh, Saudi Arabia to follow her husband, Simeon, who landed a construction job. The night work allows her to care for their seven-year-old son and avoid childcare costs.

“We need to sacrifice for the future for my family, my family's need. We came here for job. I take care of [our son] in the day and then, the night, [it’s] my husband. So it's balance.”

She enjoys the time with her son. “We have a lot of fun together, sometimes we come here shopping, sometimes we play together, he teaches me how to play a game and what he’s doing in the school.”

She says she comes to work with a smile. “I like … the people around me … laughing and talking,  no disagree, no hurt feelings.

I love working here … I feel safe and comfortable, I don't know why. Maybe because of the people around me.

Agnes Balente

Health experts and unions fear that too few employers have policies in place to mitigate the risks associated with night work.

Signal is working with health and safety regulator Worksafe to review its guidance on shift work.  

“In the past, I think that information available to our workforce has been appallingly poor,” she says. “Worksafe absolutely has a crucial role to play.” 

Catherine Epps is the agency’s head of health and technical services.

Worksafe previously focused on preventing work-related injuries, but is now shifting attention to ill-health. 

A worker is 15 times more likely to die from a disease than from a workplace accident, and work-related health deaths could be as many as 900 per year, a recent study found.

“We're trying to understand how significant the health effects of work are in New Zealand. We've carried out a worker exposure survey and we intend to repeat that again every two or three years,” Epps says.

“We want to really promote the concept of good work design. So that employers and workers really understand what they need to do to create a mentally healthy work environment. That might be big picture things like eliminating night shift work all together. But it may equally be making sure … employers design a workspace that is well-ventilated, where workers can take a break, have good access to food and drink.”

Supermarket worker Warren Smith takes a dinner break.

Supermarket worker Warren Smith takes a dinner break.

Karyn O’Keefe, of the Sleep/Wake Research Centre at Massey University, helped create the Safer Nursing Project, aimed at raising awareness and creating a code of practice on managing fatigue for DHBs.

Their nationwide study of nurses in acute care (like surgical, mental health, emergency, and intensive care wards) found 38 per cent had a sleep problem lasting more than six months, 30 per cent recalled a fatigue-related clinical error in the previous six months. And 65 per cent had felt sleepy at the wheel in the previous year.

O’Keefe worked nights for five years in a clinical sleep laboratory.

“I am a bit of a night owl so I found it probably easier than some do. But it wasn't until I finished working shift work that I realised how different life could be if I could get enough sleep.

“Just being able to feel more clear-minded and enjoy my time away from work. It's really hard to juggle social, family, household and work with getting enough sleep.”

A fleet of milk tankers are on the road every day, and through the night, with people like Darren Mason behind the wheel.

A fleet of milk tankers are on the road every day, and through the night, with people like Darren Mason behind the wheel.

Paul Jarvie, of the Employers & Manufacturers Association, says awareness about the dangers of fatigue is more pronounced in high-risk industries like trucking. 

Many employers do provide information about sleep deprivation, nutrition and hydration, he says. But many are small businesses with limited resources.

“In the main, companies do recognise it. And there is a lot of effort by employers to inform and make the staff aware of the need to get good quality sleep during the day.

“But having said that, I think it'd be fair to say that the long term health effects may not be as well-known. I would agree entirely that the whole country, in fact all Western countries, needs a lot more effort looking into the health effects of work and how to mitigate those.”

Jarvie points to research that says workers need two consecutive nights of sleep, between 10pm and 6am to recover from “sleep debt”.

“We do know that rotating shift patterns can be quite hard. There's been a lot of science done on this.

“Unfortunately you can’t bank sleep so it's all about having the ability for people to have two consecutive nights of sleep.

“It's quite well-known that people who work night shift tend to select the pattern of work that works best for them. So, rather than having a rotating shift pattern, the employer may just provide a permanent night shift pattern.”

Jonathan Holdaway works at night when traffic is at a minimum.

Jonathan Holdaway works at night when traffic is at a minimum.

Jonathan Holdaway, 35, is one who shifts between day and night time work. A traffic engineer, he typically works only a few night shifts in a month. But with four children - aged six, seven-year-old twins and a nine year-old - sleeping during the day isn’t easy.

“My personal strategy is just to sleep and in the morning don't set my alarm … typically the first night shift I find that quite hard.”

But, Holdaway says, it has its benefits.

“You can go to the bank in the daytime, do your grocery shopping. It does give me the opportunity to see different parts of my life at home.”

For E-tū’s McCully, repaying the “sleep debt” is critically important.

“There’s a lot of talk about what a post-Covid society could look like and I wonder whether it has given us a better understanding of what we're missing when we prioritise work at all hours of the day. 

“I think there are some principles around how we rebuild our society. What does the future of work need to be if we don't want people to get these long term illnesses and have these issues?” she says.

“The costs of those sorts of things are ultimately externalised. It is pushed to the state, either to deal with those health conditions that are a slow creep, whether it's diabetes, cancer or depression.

“It's our society and it's taxpayers that end up footing the bill and managing the social risks of a system that operates in that way.”

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Words: Andrea Vance

Visuals: Iain McGregor and Mark Taylor

Data graphics: Felippe Rodrigues

Design & layout: Aaron Wood

Editor: John Hartevelt

Executive Editor: Bernadette Courtney