Sleeping into the crash
Most of us know the dangers associated with DUI. On the other hand, many of us do not know that sleepiness at the wheel can have the same tragic consequences. According to many published scientific studies 20-30% of all car crashes are due to falling asleep at the wheel. In most cases the cause of this sleepiness is related to what sleep scientists call a sleep debt. A sleep debt caused by lost sleep. What many of us do not know is that a sleep debt can be cumulative. If your body needs 8 hours a night to make up for the time spent awake then a daily sleep loss of 1 hour (7 hours of sleep a night) will amount to a total sleep debt of 7 hours at the end of the week. The sleep debt will increase what we call the “homeostatic sleep drive”.
Additionally, sleepiness can also be caused by an underlying sleep disorder such as sleep apnea, insomnia or narcolepsy.
Sleepiness will have a negative impact on reaction time and may also lead to a miscalculation of
- The current speed
- Distance travelled
- The distance to obstacles on the road
Besides the homeostatic sleep drive human sleep-wake regulation is also influenced by what we call the “circadian sleep drive”. This second sleep drive is regulated by the internal clock in our brain. This clock is designed to downregulate our waking potential in the early afternoon between 1 pm and 3 pm and in the early night time between 2 am und 4 am. Consequently, most car crashes happen around those time periods within the 24-hour cycle. The circadian component is aggravated by the homeostatic component or an underlying sleep disorder.
Four typical misconceptions
- Caffeine keeps us awake
Coffe and Colaare not a suitable surrogate for sleep! Although they can give us a temporary boost in alertness, they cannot prevent us from falling asleep at the wheel. Falling briefly asleep (1 to 5 seconds) may mean travelling unconsciously a distance of 100 to 500 feet at a speed of 60 miles an hour.
- We are able to predict the time of sleep onset
Many of us believe that they can predict the precise timing of falling asleep. A study conducted by Anna Itoi and published in 1993 (study funded by the AAA Foundation, available through the internet) has shown that this is not the case. Thus, whenever we feel sleepy at the wheel we should stop and try to take a nap. Only continue driving if you have napped!
- We only need 5 hours of sleep
Few people know that the average sleep need of humans is between 7 and 8 hours to be rested the next day. And some need even more. If you frequently go to bed too late or get up too early in the morning, or both, chances are that you have acquired a significant sleep debt, making you vulnerable for sleepiness during the day. However, if you sleep consistently more than 7 hours within a 24-hour cycle and are still sleepy during the day you may have an underlying sleep disorder. If for some reason you are not able to get enough sleep during the week try to sleep in on the weekends or take naps to make up for some of your weekly sleep debt.
- Crash-free driving record = safe driver
It is the last straw that breaks the camel’s back.
Deadly cocktail: Sleepiness + alcohol
We all know that DUI is unacceptable. As mentioned before sleepiness can have the same effect on driving ability like alcohol. Sleepiness in addition to alcohol potentiates the risk of having a crash substantially. Thus, sleepiness can increase the effect of one drink on your driving ability two to fivefold.
Don’t drive: Typical warning signs
There are a few typical signs signaling you not to get behind the wheel:
- Blurry vision
- Heavy eyelids
- Constant yawning
- Wandering thoughts
- Inability to remember the last few miles driven
- Weaving driving style
- Jerky steering motions
If you experience one or more of these signs make a safe stop and try to sleep. Lock the doors.
Sleep and driving: 5 reccomendations
- Always be rested, especially when planning a longer trip
- Drive at times you would normally be awake
- Try not to drive between midnight and 6 am
- Take frequent breaks. If possible try to take a nap during those breaks
- Drive with a companion. Conversations help keeping you awake. Your companion may be more aware of your sleepiness at the wheel than you can be. And your companion can take over if you are sleepy.