Sleep isn't an option -- it's a biological necessity. Research is increasingly showing that forgoing the recommended bare minimum of seven hours of sleep at night can have dire consequences for your body's health and mental wellbeing. Now, new research is casting new light on the link between sleep and longevity from a genetic perspective, showing excessive daytime sleepiness is negatively associated with a DNA marker for longevity.
Healthy sleep, healthy chromosomes
Every day, every hour, every second one of the most important events in life is going on in your body—cells are dividing. Right now as you’re reading this sentence, somewhere cells are dividing, but each replication comes at a cost.
Due to the way DNA replication is performed in eukaryotic cells (that’s us!), the protective ends of our chromosomes, known as telomeres, shorten during these cellular replication cycles.
Telomeres have been likened to shoelace caps that protect the end of chromosomes from degradation. But just like a shoelace without a cap will unravel and eventually break its fabric, so will severely shortened telomeres trigger the malfunction of cellular division, a biological process known as senescence.
Over time, the accumulation of senescent cells is one of the leading factors contributing to aging. Research has linked shortened telomeres to cancer, cardiovascular disease, cognitive decline, even bone loss. On the flip side, longer telomeres are tied to a longer lifespan and generally higher capacity for physical activity. For these reasons, telomere length can be used to gauge a person's true biological age, which can be higher or lower than the actual chronological age, depending on the person.
In 2017, Joshua Bock, a researcher at the Mayo Clinic in Rochester, Minnesota, along with colleagues were interested in finding potential DNA markers associated with sleep apnea, a potentially serious sleep disorder in which breathing repeatedly stops and starts. These temporary breathing lapses cause lower-quality sleep and affect the body’s supply of oxygen. Around 25 million Americans are believed to have some form of sleep apnea.
The study in question found that people with sleep apnea had longer than expected telomeres for their chronological age. This was peculiar since longer telomeres are associated with a longer lifespan. Yet previous research showed that sleepiness is associated with both cardiovascular risk and shorter telomeres.
In order to clear up with apparent contradiction, the researchers performed a new study using the same 170 blood samples from the original 2017 study. Back then, each participant also completed a questionnaire, including questions on whether or not they were experiencing excessive daytime sleepiness.
The participants were divided into four distinct groups: those with daytime sleepiness and sleep apnea, daytime sleepiness and no sleep apnea, no daytime sleepiness but with sleep apnea, and finally neither daytime sleepiness nor sleep apnea.
This time, when the telomere lengths were measured the results made sense. When looking solely at those with excessive daytime sleepiness and those with both daytime sleepiness and sleep apnea, these participants had shorter than expected telomeres.
Excessive daytime sleepiness (hypersomnia) is a condition where people fall asleep repeatedly during the day; sometimes in the middle of eating a meal or during a conversation. The most common causes of excessive daytime sleepiness are sleep deprivation, obstructive sleep apnea, and sedating medications.
In light of these most recent findings, daytime sleepiness can also be connected to your chromosomes. Unfortunately, this means that daytime sleepiness may be a lot more concerning than previously believed since it is associated with a shorter lifespan.
“Sleep isn't a luxury,” Bock told Inverse. “It's something that you should do every day, like eating healthy and exercising. Sleep needs to be in that conversation.”
Before anyone freaks out about their napping routine, the researchers add the caveat that sleepiness is subjective. This is why Bock and colleagues plan on performing a new study in which the participants' sleep patterns and overall sleepiness are more thoroughly assessed than by a simple 'yes' or 'no' questionnaire. It's also worth noting that it is still unclear how telomere length relates to lifespan quantitatively, in the sense that research has yet to uncover a formula that relates the number of missing base pairs in telomere length with the number of months or years crossed off your lifespan. But we're getting there.