Updated: December 9, 2019
By: Mary Sweeney RN, BSN, CEN, ONN-CG
You're Not Alone
Think back over your history of driving a car - have you ever been exhausted but gotten behind the wheel anyway? You're not alone. In fact, a recent study performed by the American Automobile Association (AAA) revealed that 40% of drivers surveyed had fallen asleep behind the wheel of a car at least once in their lifetime. One in six deadly car accidents this year will occur because of driver drowsiness, and one in eight accidents will result in someone from the car being hospitalized. These are alarming statistics - so, why does it happen?
We live in a society that doesn't stop - there's always something to do and somewhere to be, and it doesn't matter how old you are. Being aware of your body's limitations and understanding your sleep cycle can go a long way in preventing drowsy driving and the accidents that sometimes occur as a result. Let's talk about the facts and how you can keep yourself (and others) safe on the roads.
What Happens When We Fall Asleep?
To understand drowsy driving, it’s important to also understand the human sleep-wake cycle. A normal sleep cycle lasts about 90 minutes and can be broken down into two different types: Rapid eye movement (REM) sleep and non-REM (NREM) sleep. Within those two different types, there are 4 stages of sleep – here’s a breakdown:
Stage 1: This first stage of NREM sleep is a light sleep, lasting only a few minutes or so. Here, your body is preparing to fall into a deeper sleep, your eye movements slow down, and your brain begins producing alpha and theta waves. During this stage, you can be awoken easily since you’re only lightly sleeping.
Stage 2: During this NREM stage, you’re still lightly sleeping but your heart rate slows down, your muscles relax significantly and your body temperature decreases slightly. Eye movements will slow down during this stage, and your brain waves slow down with occasional increases in activity.
Stage 3: This NREM stage is restorative sleep, the kind that makes you feel refreshed. If someone were to wake you up during this stage, you would likely feel disoriented for a few minutes before realizing your surroundings. Our eye movements slow down or stop, and it’s very difficult to wake us up. This stage is an important one – it’s where your body starts repairing muscle, strengthening your immune system, and other vital processes.
Rapid eye movement (REM) sleep: During REM sleep, our eye movements increase dramatically, as the name suggests. REM sleep is the stage where you dream the most, and it’s thought that the eye movements are related to the dreaming that you’re doing. During this stage, most of your muscles are in a paralyzed state, to keep you from acting out your dreams. Don’t worry though, the important muscles like your heart and diaphragm aren’t paralyzed and are working like they’re supposed to!
While the average sleep cycle lasts 90 minutes, you will go through several cycles of varying lengths during one night. During your first few sleep cycles, you’ll go through longer cycles of NREM sleep, followed by a few cycles of REM sleep. As if that doesn’t complicate things enough, there has been research that shows that the time of day can affect what type of sleep you get. For example, it is thought that most NREM sleep happens between the hours of 11pm and 3am, and REM sleep more often happens between 3am and 7am (source).
What Is The Circadian Rhythm?
Our bodies have internal clocks that every organ system uses to function on a daily basis. When we talk about sleep, these clocks tell us when it’s time to be awake and when it’s time to go to sleep. They regulate our sleep cycles by giving us our circadian rhythms, which are the schedules our bodies follow for the physical and mental changes we go through on a daily basis. Circadian rhythms regulate the body’s sleep cycles by sending a series of messages from the hypothalamus to your brain to the rest of your body. This is important in regulating the production of melatonin, the hormone that makes you feel tired. Melatonin is naturally produced by the body when there is little to no natural light, usually at night. Its production decreases during daylight hours, which is why we feel awake during the day and sleepy at night.
How Much Sleep Do We Need?
In this day and age with everyone's "go go go!" attitudes, it can be hard to get a good night's sleep, and even harder to get enough sleep in general (adults need 7-9 hours per night). And, as many of us already know, your life and everyday demands don't disappear if you're not sleeping well. Whether you're a night shift worker, a parent of a new baby (or a toddler that is constantly wound up), or an insomniac, there are a ton of reasons why you might be tired. Because of this, a majority of Americans will get behind the wheel of a car with less than the recommended amount of sleep. In fact, in a 2009 study, 7 out of 10 adult survey respondents reported drowsy driving within the last month.
If that statistic doesn't scare you, this will. If you are awake for 20 hours straight and then drive a car, that's the equivalent of driving with a blood alcohol level of 0.08, which is the legal limit. As with driving under the influence of alcohol, driving while drowsy impairs your reaction time, making it more difficult to quickly and appropriately respond to hazards that may appear while you are on the road. As eloquently stated by the National Safety Council, "drowsy driving is impaired driving."
Why Is Drowsy Driving Dangerous?
According to the National Sleep Foundation, here are some signs that you may be too tired to drive:
- Difficulty focusing, frequent blinking, or heavy eyelids
- Daydreaming; wandering/disconnected thoughts
- Trouble remembering the last few miles driven; missing exits or traffic signs
- Yawning repeatedly or rubbing your eyes
- Trouble keeping your head up
- Drifting from your lane, tailgating, or hitting a shoulder rumble strip
- Feeling restless and irritable
If you feel like you are experiencing any of these signs or symptoms, get off the road as soon as you safely can.
Tips and Strategies to Avoid Drowsy Driving
Here are some tips and strategies that may help you avoid driving while drowsy:
The obvious. Get enough sleep! An adult needs seven to nine hours of sleep per night to function optimally, and a teenager needs eight to ten hours of sleep. Getting less than the recommended amount of sleep per night puts you at greater risk for driving while drowsy.
Use crash avoidance technology. Many newer model cars are equipped with sensors that alert you when you are drifting out of your lane or when you're about to collide with an object. If you work odd hours or find yourself frequently driving while tired, consider upgrading your car to one that is equipped with these features.
Get off the road. If you start to experience the above signs and symptoms, pull off the road as soon as it is safe to do so. If necessary, find a safe place to park and take a 20-minute nap before hitting the road again, it may give you a small boost of energy to get you safely home.
Create a good sleep environment. As we discuss in other sleep guides, creating an optimal sleep environment is crucial to getting quality sleep. Ensure your room is dark, and consider using blackout curtains if you are working nights and sleeping during the day. Keep your thermostat between 60-69 degrees, as cooler sleeping environments tend to improve sleep quality.
Consider melatonin. Melatonin supplements can be helpful if you have trouble falling or staying asleep. Be sure to consult your doctor or healthcare provider before starting any supplements.
Be aware of medication side effects. Know how your prescription medications affect you! Read the labels and side effects on every new medication you start, and be sure you know how it affects you before you drive.
Drowsy driving causes over 300,000 motor vehicle accidents each year, don’t be one of them! While being tired is sometimes unavoidable, getting behind the wheel of a car while impaired IS AVOIDABLE. Remember, drowsy driving is impaired driving – don’t become a statistic.