Circadian rhythms shift as we age—making older adults want to go to bed earlier

Studies suggest when you sleep is as important as how much you get.

The body's sleep-wake cycle is one of its many circadian rhythms

The body's sleep-wake cycle is one of its many circadian rhythms, which are behaviors or biological processes that exhibit 24-hour patterns. These rhythms are deeply impacted by light exposure, food availability, and much more, meaning where you live impacts your sleep.

External factors, not aging itself, lead to sleep loss in older adults

Though it is often believed that people need less sleep as they age, the recommended sleep guidelines for all adult age groups are almost identical. However, factors such as medication use, lack of physical activity, and loneliness can lead to sleep problems, and thereby lead older people to believe that they actually need less sleep than they do.

Artificial lighting and modern practices like working late are linked with sleep shifts

An analysis of five adults participating in a German reality program that tasked them with living in a Stone-Age-like settlement for 2.5 months, provided some insights into how modern conditions may have shifted our circadian rhythms. The participants slept about 90 minutes more under these conditions, and went to bed earlier and rose earlier, raising questions about how circadian rhythms, sleep, and sleep quality are affected by modern lifestyles.

Temperature and certain medications can also affect your circadian rhythms

Although light and dark have the largest influence on circadian rhythms, temperature, stress, and certain medications are among the factors that also play a role. Persistent trouble sleeping or staying asleep may signal it’s time to see your doctor to get a better sleep-wake schedule.

Babies don't develop a circadian rhythm right away

Newborns don't develop circadian rhythm until they are a few months old, which helps to explain their erratic sleep schedules. When they're around three months old they begin to release melatonin, which influences sleep, and around the same time they develop more regular sleeping routines.

Most things you would get tested for at the doctor’s office are influenced by circadian rhythm

In this video, a Salk Institute Researcher offers daily habit tips focused on aligning with your circadian rhythms. She notes heart rate and blood pressure are highest in the afternoon, for example, and there’s a triglyceride peak in the morning. Generally, she says, it’s a good idea to schedule your doctor’s checkups at the same time of day each year so there’s consistency across your data.

Circadian rhythm disruption can influence various mental health disorders

This 2020 research overview surveys the relationship between disrupted circadian clocks and disorders including schizophrenia, anxiety, and bipolar disorder. It incorporates findings and therapeutic approaches drawing from human night shift studies and jet lag studies alongside animal research.

Parasites have circadian rhythms, too

Researchers are working to unravel how circadian rhythms of parasites and their hosts affect one another. They’re investigating how to potentially target and disrupt those clocks for disease treatments.

There is a best way to wake up—but not a best time

Sleep and circadian rhythm researchers say that waking up at a consistent time each day—even on weekends—and viewing morning sunlight are the best ways to keep body functions running at their peak. (Some users may encounter a paywall.)

Chronobiologists study the effect of time on biological cycles

Circadian rhythms were first observed in the 1700s, when French astronomer Jean-Jacques D'Ortous de Mairan put a plant in a dark room and watched it still respond to day and night cycles, setting off further studies about specific light-dark biological cycles, an area of inquiry that continues today with the human "clock proteins" at the molecular level.

Five patterns may define how we sleep—not just night owl or early bird.

Emulating Earth’s light-dark cycle is important for astronaut health and safety

Astronauts aboard the International Space Station experience 16 daily sunrises, but scientists have learned to try to promote circadian rhythms by phasing through several light settings aboard the ISS to improve astronauts’ sleep and productivity.

Genetics play a role in the reliability of the body's biological clocks

Growing evidence suggests genetics influence when, how long, and how well one sleeps, meaning insomnia may have a genetic component. While exact insomnia biomarkers have yet to be determined, some genes, including those related to psychiatric disorders, have been implicated.

'Zeitgebers' like light are external cues for the circadian clock

German for "time giver" or "time cues," common external zeitgebers include sunlight, food, and physical activity. The timing of these external influences can shift circadian clocks or lead to irregularities: A 2018 study, for example, found that later light exposure and meals were linked to later timing of peak activity and bedtimes.

One theory claims the retinae of SAD patients may fail to adjust to less light in winter

Most people’s eyes become more sensitive to light in the winter months, but some do not. This failure to adjust causes ripple effects on those individuals’ biological clocks. This Ted-ED video provides a clear, brief, narrative explanation of the condition in six minutes.

There is a template for how to live a better, healthier day, and it includes a digital sunset

Science suggests that early-morning exercise, later-morning peak work or social time, consistent exercise, and a "digital sunset"—starting to turn down the lights in the evening and avoid screens—are important for circadian health.

Chronological versus biological age

Science has come to understand different types of aging. What we call age is simply the number of years since birth, or chronological age. At the cellular level, biological aging happens at different rates for different people, and explains why some seem to age more quickly (or slowly).

SAD disrupts melatonin secretion, producing it longer in the morning

The hormone is secreted from the pineal gland in the brain and is key to the timing of sleep. However, the substance does not generate sleep itself. With seasonal affective disorder, the body misperceives the photoperiod—the time with light—and the cycle of sleeping and waking gets off-phase, leading to issues with circadian rhythms.

What happens when we sleep

Sleep is a highly specialized and complex process that begins via signals from a region of the brain called the hypothalamus. As explained in this overview video from The Economist, the hypothalamus maintains our circadian rhythm by using light cues from our environment to regulate sleep via a compound known as melatonin. Once asleep, the brain begins the "sleep cycle" and progresses through the four stages of sleep over and over again each night.

The side effects of falling back and springing forward

Daylight saving time can interfere with a person’s sleep schedule, but it also has been linked to increased rates of depression, heart attack, stroke, cancer, and car accidents. UT Southwestern’s Dr. Joseph Takahashi explains why the time change is bad for your brain and health.

The design of a psychiatric ward in Norway aims to integrate more circadian rhythm-friendly lights as part of its treatment protocols for conditions including psychosis, severe depression, and more.

Ending daylight saving time may prevent as many as 300,000 strokes annually

Changing clocks twice a year disrupts circadian rhythms, which last an average of 24 hours and 12 minutes. Studies have shown that permanent daylight saving time provides fewer health benefits than standard time.

Daylight Saving Time is linked to a rise in heart attacks and strokes

Losing an hour of sleep with seasonal time changes is not good for our health and it’s linked to risks for the first couple days of Daylight Saving Time, including a short-term rise in heart attacks and strokes. Scientists theorize these elevated risks are linked to the disruption to the body’s circadian rhythm.

Biological aging tests assess the breakdown of physiological systems

Known as aging clocks, these tests compare various metrics, like DNA methylation patterns and protein profiles, to healthy baselines. However, the non-uniformity of these baselines across individuals limits testing accuracy and prevents their clinical use.

Can humans delay or reverse old age?

We're not sure yet. Researchers at the University of California San Francisco are studying why some conditions and behaviors, such as low-oxygen environments and exercise, benefit the aging process, hoping to reveal potential health applications. Some of this research focuses on klotho, a naturally occurring age-regulating hormone named after the Greek Fate Clotho. Animal studies on klotho brain injections found subjects had improved memory recall and age-related degeneration resistance.

The lost medieval habit of 'two sleeps'

While most people accept a single seven-to-nine-hour nightly slumber is ideal, the approach is a relatively modern idea. For centuries, interrupted sleep was the norm, with historians uncovering descriptions of two periods of sleep during the normal 24-hour cycle.

Aging is a complex biological process affecting our cells, tissues, and organs.

How much sleep do you need?

When it comes to how much sleep you need, age matters—and, for your health, it's important to be well rested. Young children between the ages of one and three need the most sleep: It’s recommended that toddlers get between 11 and 14 hours of...

Single-cell organisms have circadian clocks that direct daily biochemical routines

Cyanobacteria, a type of light-sensitive bacteria, use this clock to signal when to alternate between making organic compounds through photosynthesis and when to convert atmospheric nitrogen into usable ammonia. Upregulating photosynthetic machinery before dawn helps ensure efficient photosynthesis.

Humans may have evolved to need less sleep.

Sleep deprivation leads to the buildup of dangerous molecules in the gut.

Lack of sunlight during Arctic winters can fuel a winter slump and a circadian disconnect.

Individuals typically spend less time with others as they get older

At younger ages, we spend much of our time with parents, siblings, and friends. Eventually, our lifestyle changes to include work, a spouse, and children of our own. In later life, children often move out, and spouses unfortunately pass away, leading to more time spent alone.

World records are often broken later in the day—and scientists wonder if muscle clocks explain the difference.

The brain will attempt to rest itself in periods of chronic sleep deprivation

Skimping on sleep lengthens reaction times and blunts decision-making skills. At a certain point, the brain will try to sneak sleep where it can, shifting sections offline even as you remain awake. Going without sleep raises blood pressure, undermines the immune system, and increases one's risk of dementia.

Each part of the human body experiences aging differently

With global average life expectancy cresting at 73 years, understanding how the body ages is imperative to effective medical treatment and maintaining a desired quality of life. This 13-minute video dives into how the body and its organs age "from head to toe."

Astronauts follow strict schedules to mimic Earth days and stay healthy in space

Experiencing 15 sunrises and sunsets a day while aboard the International Space Station, visitors preserve their circadian rhythms and mental health with fixed timetables. Astronauts have described sleep as living in a vacuum cleaner due to ongoing air filtration.

What it's like to live with insomnia

The biological process Shakespeare referred to as the chief nourisher of life's feast is necessary for the body and mind to rest and repair from the activities of daily life. As sleep evades the exhausted, sufferers also lose emotional stability, mental clarity, social connections, and more while simultaneously gaining waves of interrupted biological processes that can lead to disease and death.

How aging degrades neural functioning in the brain over time

Aging affects the brain perhaps more than any other organ in the body. Throughout life, the brain experiences radical shifts in the number of neurons, synaptic connections between neurons, and hormone levels that regulate our mood and processing.

The REM cycle—named for the 'Rapid Eye Movement' that occurs during this stage of intense dreaming—happens around four to six times per night.

Social jetlag—differing weekend and weekday schedules—is physiologically similar to jet lag

Recovering from schedules that drastically differ between weekends and weekdays, something that was first described in academic work in 2006, is a growing concern in public health as more research shows that consistent daily routines are important for human health.

Before alarm clocks, people relied more heavily on their circadian rhythms, humans hired to wake them, and on tools such as candle clocks that dropped pins in metal trays at roughly set intervals.

Perceived isolation ages you

Mounting evidence suggests that socialization is a vital component of maintaining good health. Research published in 2024 from Mayo Clinic researchers analyzed the social lives of more than 280,000 adults and concluded that individuals that weren't likely to participate in extracurricular social activities and get-togethers were more likely to have a biological age older than their actual age—meaning that you may be 60 but health indicators would suggest you're older.

In 2017, researchers won a Nobel Prize for their work controlling fruit fly circadian rhythms

This detailed circadian rhythm infographic breaks down a day in the biological life of a fly, providing a peek at some of the groundbreaking work that elicited a Nobel Prize in Physiology or Medicine.

Do people really look younger than they used to?

Why do people today look younger than they used to? From style to science, there are 3 surprising reasons we age differently now.

Cellular aging and deterioration leads to tissue (and overall) aging

Cells are the building blocks of life, forming tissues and organs that keep our bodies working. As we age, cellular changes have progressive consequences on both the structure and function of our organs. This article examines this complex relationship as it relates to the incremental changes associated with aging.

The formula behind super agers—those possessing health and cognitive skills of people decades younger

A study of about 1,400 super agers did not identify any underlying genetic mechanism for longevity. While researchers instead emphasized that sustainable habits involving positive social connections, sleep, mood, diet, exercise, and personal fulfillment help reduce long-term risks, there is no one-size-fits-all formula for everyone.

Similarities between human and animal sleep

Have you ever noticed the wide-ranging differences in sleep between humans and animals? Sleep as a necessity is present amongst all animal species, but the specific patterns of sleep vary widely. Just think of the differences between how an owl, a whale, and a horse might sleep. This helpful resource from the Sleep Foundation explores the relations between human and animal sleep, complete with some fascinating statistics about sleep patterns throughout the animal kingdom!

Why do we sometimes jolt awake before falling asleep?

Around 70% of people are estimated to experience the sensation of falling and jerking awake right as they're about to drift to sleep. That mysterious phenomenon is called hypnic jerking. As common as it is, hypnotic jerking remains disconcerting and hard to explain. While we don't yet have clear answers, peruse this article in Popular Science for some possible explanations as to why this happens.