Spring forward, stay alert: daylight savings sleep shift increases heart risk for drivers
- Kristen Wilson
- 4 days ago
- 3 min read
As daylight saving begins this Sunday, Kiwis may welcome the brighter evenings and promise of summer BBQs, but the switch comes with a darker side. Health data shows the sudden disruption to body clocks has measurable consequences: hospitals in Michigan, US found heart attacks spike by 24 percent on the Monday immediately following the spring shift[1], while a 2024 review of 12 studies confirmed a four percent increase in risk across the two weeks that follow[2] setting clocks an hour forward. Road crashes also climb by around six percent in the same week[3] underscoring that losing even a single hour of sleep can have serious effects on both wellbeing and road safety.
Economists at the London School of Economics estimate that ending daylight saving could deliver wellbeing gains worth roughly NZ$1,400 per person annually, with the wider toll of sleep deprivation — to which clock changes contribute — costing around NZ $680 billion worldwide each year[4].
Katrina Aubrey, Fatigue and Sleep Specialist at AutoSense, New Zealand fleet safety experts, says the health impacts of daylight saving is often underestimated, particularly for people who drive for a living.
“Our body clocks are finely tuned. Losing up to an hour of sleep — as happens every spring — disrupts circadian rhythms and increases fatigue. This sleep deprivation also affects heart health in multiple ways. Poor sleep increases inflammation, which can damage blood vessels and increase heart disease risk, and losing sleep elevates the risk of arrhythmias - irregular heart rhythms - potentially increasing the risk of stroke and heart-related issues,” says Aubrey.
“The fatigue and disruption also affects reaction time, mood and alertness — all critical for safe driving. For professional drivers who work long hours, the impact can be especially dangerous for them, and for everyone they share the road with.”
AutoSense is working with more than 800 transport operators including NZ Post, Mainfreight and Fonterra to reduce incidents and protect drivers through training and technology. The business has installed Guardian by Seeing Machines driver safety technology in 5,969 vehicles across 864 fleets in New Zealand, with the cameras monitoring fatigue and distraction events in real time, every second of the day and night.
Using AI, the technology combines cutting-edge optics and processing to continuously monitor a driver’s eye and head movements, capable of detecting early signs of drowsiness and distraction. Fatigue events are detected when the driver’s eyes are closed for 1.5 seconds or longer when travelling at or above a set speed threshold. The system issues real-time audio, visual and seat-vibration alerts to help drivers act before fatigue or inattention becomes critical. The technology includes another layer of safeguarding - any red-flagged video is assessed by a human ‘Guardian Angel’ in a call centre. The Guardian Angel looks for signs of fatigue or distraction, and will intervene by alerting the driver to take a rest from driving.
In the year to 31 July 2025, AutoSense says an astounding 19,390 driver fatigue events, and 52,553[i] distraction events were recorded by the Guardian cameras in Aotearoa.
Aubrey says, “Utilising the Guardian technology means we can identify safety issues with drivers and provide education and training to mitigate these risks before they can escalate. By shedding light on the insights that the Guardian data provides us, we hope to influence driver behaviour, making driving on New Zealand’s roads safer for everyone.”
She says that while most Kiwis enjoy the longer evenings and the chance to fire up the BBQ, losing an hour’s sleep isn’t harmless.
“Fatigue can impair you as much as alcohol, and combined with the increased cardiovascular strain from daylight saving, it creates real risk. The technology is an important tool for fleets — it’s like a low-fuel warning light for your alertness, helping drivers take action before danger strikes.
“Even small disruptions to sleep can have measurable impacts on heart health, alertness and reaction time, increasing the chance of serious incidents on the road. The combination of healthy sleep routines and knowing the signs of a heart attack, at any time of the year, can lower the road risks at this time of year.”
Aubrey applauds the New Zealand businesses who have taken road safety into their own hands and installed the life-saving technology in their fleet.
“I take my hat off to the employers who are investing in technology like Guardian, as this is undoubtedly the best defence against these road risks, helping ensure their drivers — and everyone who shares the road with them — make it home safely,” she says.
[i] AutoSense Guardian Insights for 12-months ended 30 July 2025. Total NZ vehicles: n=5,969
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