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What Is Sleep Debt And Do I Have It?

2 minute read

It’s Fatigue Free February and this month we’re digging deep into fatigue – what it looks like and how to avoid it. Approximately 20 – 30% of all car crashes are attributable to fatigue, making it one of the three leading causes of vehicle crashes in Australia.

Driving fatigued heightens the level of risk because a person who is drowsy or asleep cannot react to their surroundings, amplifying the severity of a crash.

Did you know that driving after staying up for 24 hours has the same effect as driving with a BAC of 0.1? That is double the legal BAC limit (watch about BAC HERE).

Fatigue is influenced by several factors; being awake for long periods of time, driving or doing the same task for an extended period of time, lack of quality sleep and driving at times when you would normally be asleep all pile up to make a fatigue-related crash.

The warning signs of fatigue are:

  • Constant yawning
  • Slow eye movement or constant blinking
  • Head snapping/nodding
  • Lane swerving and variations in driving speed
  • Daydreaming
  • Microsleeps – brief and unintended episodes of sleep

People who continuously do not get enough sleep start accumulating something called a sleep debt. We all need about eight hours of sleep a night to function effectively. But when we don’t get enough sleep night after night, the effects build up and put us at an increasing risk of a microsleep.

Put simply, sleep debt is the difference between the hours of sleep you need (about 8 hours) and the amount of sleep you actually get. When we have a sleep debt, our tendency to fall asleep the next day increases. The larger the sleep debt, the stronger the tendency to fall asleep, including when you are driving.

There are various short-term ways to help us ‘wake up’ such as drinking caffeine or having a nap, but we can only truly get rid of sleep debt by tackling the issue at its core – having more sleep. And even then, it can take up to four days to recover from one hour of lost sleep and up to nine days to eliminate sleep debt, studies show.

While the ‘solution’ to fatigue is simple, our day-to-day activities often get in the way of getting some much-deserved rest. To best avoid driving tired, before you get into the car, PAUSE:

P – PLAN, how long will I be driving, where can I safely stop if I feel tired?

A – ALTERNATIVE, what alternative forms of transport can I use?

U – USING, am I using any medications that can make me drowsy?

S – SLEEP, have I had enough quality sleep?

E – EXHAUSTED, am I showing any signs of exhaustion or fatigue?

As you’re driving, remember to STOP, REVIVE, SURVIVE every 1.5 – 2 hours, or when you show any signs of fatigue. Taking a 20-minute power nap can help reduce the effects of fatigue and help you feel refreshed after 3 – 4 hours.

Read about why workplace road safety is important and how to help integrate it into your workplace HERE.


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