Why Not To Be A Night Owl After 40

It’s often assumed that being an “early bird” or a “night owl” is purely a matter of genetic predisposition, and… There is indeed a genetic influence, but as it is said, “genes predispose; they don’t predetermine“.

We discussed this in detail, here: Early Bird Or Night Owl? Genes vs Environment

With that in mind, being a night owl is, for most of us, largely a modifiable thing. Some people, of course, will have things going on in their life that preclude getting an early night’s sleep, but if that’s not the case for you, then we do recommend considering shifting your chronotype to being an “early bird”, if it’s not already there.

For more about chronotypes in general, see: 5 Sleep Phenotypes, By Actual Science (Sleep Tracking, For Five Million Nights)

Why does it matter?

A team of researchers (Dr. Ana Wenzler et al.) did a large (n=23,798) study and found that night owls face a higher risk of cognitive decline compared to morning people.

As to why “after 40”, there are two reasons:

1. Biological clocks shift throughout life: people tend to be morning types in childhood, shift to evening types in adolescence, and most, but far from all, return to morning preference by around age 40.
2. Cognitive decline naturally begins most commonly after age 40, and lifestyle factors influence this process.

For this reason, the study used data from people over the age of 40, to analyze people’s chronotypes (natural sleep patterns) and their behavior over a 10-year period.

As to how much being a night owl affects the risk of cognitive decline; it was broken down by demographics, but for example in the group with the highest education level:

❝each one-hour increase in chronotype corresponded to a 0.80-point decline in cognition per decade (95 % CI: -1.34, -0.26)❞

The “night owl” chronotype was also associated with greater decline in non-verbal fluency and executive functioning among higher educated participants, highlighting the importance of targeted prevention strategies.

In terms of potentially confounding (although also relevant) factors, night owls tend to engage more in unhealthy behaviors such as smoking, drinking, poor diet, and lack of exercise—especially in the evening.

You may be thinking: “I don’t do those things”, in which case, great! But the researchers also calculated that those behaviors explain only about 25% of the cognitive decline risk among night owls.

You can read the paper in full, here: Chronotype as a potential risk factor for cognitive decline: The mediating role of sleep quality and health behaviours in a 10-year follow-up study

How should we fix it?

If you’re currently a night owl, chances are you physically cannot currently sleep earlier than you do—your brain just isn’t ready to sleep yet at the earlier hour.

What you can control, however, is your getting-up time. So, shift that earlier—gently! 15 minutes earlier per day is great—and your “getting sleepy time” in the evening will naturally shift commensurately earlier.

For reference, see also: Calculate (And Enjoy) The Perfect Night’s Sleep

Take care!