Some people jump out of bed every morning ready to start the day. We call them “morning people.” For others, getting out of bed can be tough, like scaling Everest tough.
Especially when the weather turns cold, no one likes leaving the warmth of their cozy sheets and heading to work. When I was a kid, I would lie half conscious in bed, after my Mom “woke me up,” dreaming that my bed would grow wheels and an engine, so I could attend classes under the covers.
Never happened, but it was a nice fantasy.
However, kidding aside, we all know someone who has extra trouble getting out of bed in the mornings. No matter how much sleep they get, they’re always a little groggy. They are definitely not morning people. For these folks, the inability to wake up can be an issue that hinders work performance, and may even cause regular tardiness. Other than having had a few too many drinks the night before, is there a scientific reason why certain people always seem to be groggy first thing in the morning?
Genetics could be to blame for your morning grogginess
As it turns out, there are genetic variants associated with an inability to “get up and at em'” first thing in the morning. The ADA gene is responsible for metabolizing adenosine, and enzyme long thought to be associated with sleep. Most of the research surrounding adenosine has been related to caffeine. Caffeine keeps us awake because it blocks our adenosine receptors. (R)
Your body produces adenosine as it burns ATP, the body’s main energy currency. As your ATP levels decrease, Your levels of adenosine increase, until they peak at bedtime. As you sleep, your body then gets to work metabolizing adenosine, until your levels are low again when it’s time to wake up. (R) That’s how it works for most people, but not for people with a mutation in their ADA genes.
Adenosine metabolism varies based on genotype
As the chart below demonstrates, the G allele is the common allele for most people, and denotes “normal” clearing of adenosine through the course of the night. However, the A allele (ADA G22A the “grogginess gene”), which is listed here as “risk,” shows a slow down in clearing adenosine from the body. The G allele carriers have their cleared all their adenosine by the time the alarm goes off, and are ready to start the day.
By contrast, the A carriers still have high levels of adenosine in their bodies when it’s time to wake up, making it that much harder to get moving.
|Protein||Gene||SNP Id||Major Allele/Minor Allele (Risk)||Effect|
|ADA||ADA||rs73598374||G/A||G (Asp) > A (Asn)|
A associated with 35% reduction in ADA activity. Adenosine is not converted as efficiently and so not cleared by morning. (R)
Leads to feeling of sleepiness, impaired attention, and vigor. (R)
However, quality of deep sleep improved. (R)
Carriers of the ADA G22A polymorphism (A variant) can fall asleep normally, and get deep rest, but they have such high levels of adenosine that they’re unable to wake up as quickly. Although those carrying the “grogginess gene” have a tougher time waking up, they also sleep better, and can still get good sleep after consuming caffeine, as this study demonstrates.
Perhaps a little extra adenosine in the mornings isn’t such a bad thing.