“People with a deficient CAR may have deficient levels of energy—or may not even be able to wake up at all,” says Raj Dasgupta, MD, an associate professor of sleep medicine at the University of Southern California and a fellow of the American Academy of Sleep Medicine.
It’s also a highly influenceable process, with research suggesting that numerous factors—including many that are well within our control—can impact whether or not we have a healthy CAR. For example, waking up early in the morning tends to result in an increased CAR, while sleeping in the presence of pervasive low-frequency noises (think: traffic and other sounds of the city) can seriously dampen it. Other factors that have been shown to dampen CAR include fatigue and sleeping while in pain, while wakening in sun-like light as opposed to pitch black — is associated with an increased CAR.
According to Dr. Dasgupta, the hormonal shifts that can result from such ambient and environmental factors suggest that many people are looking at healthy sleep the wrong way. In particular, people are often concerned about how to fall asleep, but neglect the factors that are important to maintaining high-quality rest once they’ve fallen asleep.
“Me and you could each sleep eight hours, but is that eight hours of quality sleep?” says Dr. Dasgupta.
“When people ask me if you can die from poor sleep, I say that of course you can die. You can have a car accident, but there are also the long-term effects: Heart attack, diabetes, high blood pressure. And your cortisol levels are an important marker for these.”