There are many jokes that center around older adults waking up before the sun, and even more about teenagers’ late-sleeping habits. Turns out there’s truth to them: The time our body naturally goes to sleep and wakes up is not only part of our genetics, but part of the natural aging process, too.
As we age, our bodies change both internally and externally, which is a major factor behind the sleep changes that come later in life. “Like most of the things that change with age, there’s not just one reason, and they are all interconnected,” said Cindy Lustig, a professor of psychology at the University of Michigan.
We asked Lustig and other experts to break down the main reasons why this occurs, and what you can do to push back if you just want those few extra hours of Zzzs.
Earlier wake times are part of the natural aging process.
Like other aspects of our physical and mental health, the brain becomes less responsive as we age.
“The wiring of the brain is likely not sensing … and responding to the inputs as well as it should because it’s an aging brain,” said Dr. Sairam Parthasarathy, the director of the Center for Sleep and Circadian Sciences at the University of Arizona Health Sciences. These inputs include sunset, sunlight, meals, social cues and physical activity that help mark where we are in a day.
“These are all what we call time givers, or they give time to the brain,” he said. In other words, they help the brain sense where it is in the 24-hour circadian cycle.
So, for a younger person, dinner time may help the brain understand that bedtime is in a few hours; for someone older, this connection may not happen.
The nerves that are supposed to give the brain time cues have undergone the same amount of degeneration as the brain, Parthasarathy said. This inability to sense time cues is part of the reason why older people tend to get tired before their children or grandchildren. And, as a result, wake up fully rested and earlier than the rest of the world.
The light our eyes take in is part of it, too.
“Interestingly, one of [the reasons] seems to be that the vision changes that come with age reduce the intensity of the degree of light stimulation that our brain receives, which plays an important role in ‘setting’ our circadian clock and keeping it on track,” Lustig said.
Parthasarathy explained that this is especially true for people with cataracts, a common eye condition that impacts more than 50% of Americans ages 80 and up, according to the National Institutes of Health. Cataracts cause blurred vision, double vision and general trouble seeing.
“If there’s cataracts, the evening light doesn’t go into the eyes as much, so, according to the brain, sunset is earlier than when it actually set,” Parthasarathy said.
Why does this matter? Since there is less light getting into the eyes because of the vision issues cataracts cause, the body starts to release melatonin (the sleep hormone) earlier than it should. For younger people, melatonin “starts rising after sunset,” Parthasarathy said, which is why you generally feel tired a few hours after. For people with cataracts whose brain thinks sunset was earlier, their perceived sunset is earlier, which makes them tired sooner in the evening. And going to bed sooner means waking up earlier.
“There is some evidence that cataract removal surgery can help improve sleep quality and duration by helping those light cues get through,” Lustig said.
If this is you, there are a few steps you can take to sleep better.
According to Parthasarathy, if you struggle with this issue, you should ignore the advice to put away the screens and instead expose yourself to bright light in the late evening. This can mean going for a walk outside before the sun sets, reading a book on a bright iPad, getting artificial lights for your home or watching TV on a bright screen.
These bright lights will tell the brain that the sun hasn’t set yet, which will hold the melatonin production, he said. To help yourself stay up a little later (and sleep a little later as a result), Parthasarathy said you should try these things 30 to 60 minutes before sunset, which will vary depending on the time of year and where you live in the U.S.
The exact amount of time you should expose yourself to bright light varies, and might take a bit of trial and error, but he said you should aim for about two hours of exposure — and should certainly keep the light on after sunset.
Lustig added you should avoid alcohol before bed — “while that nightcap might make you sleepy, it actually disrupts the quality of your sleep.” Additionally, she said exercise can help you get better sleep and the morning sun can help your circadian clock follow the sun’s rise and set cues.
All in all, changes in sleep patterns are a part of life. While some of these factors are out of your control, you can also counteract them with healthy habits so you can get your best rest.