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

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

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.

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.)

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

Throughout our lives our internal biological clocks shift. Early-to-rise toddlers become hard-to-wake teens and eventually early-to-sleep seniors. Circadian rhythm fluctuations throughout our life cycle explain some of these changes.

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 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.

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.

How meal timing factors into health outcomes

The world is trending toward weight gain, a development that comes with a corresponding rise in risk for health conditions, including diabetes and heart disease. This article explores how meal timing has become a factor in nutrition and weight maintenance.

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.

Certain vaccinations may be more effective when given around the middle of the day.

Doctors are prescribing social activities—and seeing good results

Physicians, especially in the UK, are asking patients what they enjoy and then prescribing a consistent regimen of doing that type of activity to improve fitness and overall health, including community exercise classes, volunteering, and spending time in nature. This approach may provide better incentives to stick with an activity.

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.

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.

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.

Heart attacks are less harmful at night

When heart attacks occur during the day they typically do more harm to the heart tissue than if they occur at night. A 2025 study suggests that daytime heart attacks have higher levels of immune cells called neutrophils to contend with and they appear to worsen the injury. Scientists confirmed this same pattern in experiments with mice. (Some readers may experience a paywall.)

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.

Addressing lifestyle factors, which influence inflammation, can cure some chronic diseases

In this video, a physician claims that he reversed a patient's Type 2 diabetes in six weeks by addressing inflammation drivers such as diet. More broadly, he argues that society needs to better consider and address numerous disease factors that are modulated by inflammation, such as stress, sleep, diet, and movement.

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.

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

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.

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.

Staying on standard time permanently would slightly reduce obesity and stroke risk

A 2025 study that examined time changes found that permanently changing to standard time would slightly reduce obesity and stroke risk more than switching to permanent daylight saving time.

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.

'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.

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.

Blood pressure readings correspond to the peaks and valleys of heart beats

Pushing 2,000 gallons of blood through the body every day exerts a force known as blood pressure. Blood pressure is highest during the heart's contractile phase, known as systole, which forces blood through the circulatory system, and lowest during the heart's resting phase between beats, known as diastole.

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.

Studying the circadian clock of a tiny swimming polar creature may help forecast polar ecosystem health

A 2025 study found that Antarctic krill, a food chain staple in the Southern Ocean, have an internal biological clock that helps regulate its swimming patterns and helps the tiny shrimp-like animals adapt to daily and seasonal environmental changes. Better understanding of how the clock and light cues interact may help scientists understand how well the species will respond to pronounced climate change in the polar region.

Patient portals offer a good opportunity to track your healthcare records and communicate with doctors, but they also allow patients to see test results without context, which can cause unnecessary concern.

SAD uniquely affects people with attention-deficit hyperactivity disorder

Those with ADHD—chronic issues with attention and executive function—are primed for SAD. Many are disproportionately evening chronotypes (more awake in the evening), have a delayed sleep phase, and have low sensitivity to light in the morning. This podcast explores the overlap between these two groups.

Small ways to improve your health today: an animated guide

What are some ways that you could start making a positive impact on your health today? This animated gallery overviews several health topics, including sleep and hydration, and offers ways to improve that aspect of your life. Clicking on the...

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.

Moving your body every day is key to longevity

In an era of biohacking, where millionaires subject themselves to draconian routines and tests to de-age themselves, one study suggests a super simple key predictor of mortality: more than any other trait, how much subjects moved determined how long they'd live. Movement mattered even more than age in predicting overall life longevity. Researchers suggest this means we should all simply get outside a bit more. Read more about the study here.

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.

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.

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.

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

At-home genetic testing results commonly led users to healthier lifestyles

Italian research that aimed to investigate what people do longer-term after receiving direct-to-consumer genetic test results indicated that whether the results were positive or negative, people tended to adopt a healthier diet after receiving the results, and they'd still maintained it a year after receiving their results. Some users also reported an overall reduction in stress over their health concerns. (Some users may encounter a paywall.)

Ten things to know about your heart

Your heart does amazing things day in and day out. Its main job is crucial: It keeps oxygenated blood circulating throughout your body. Did you know that, other than your cornea, every cell in your body gets blood from your heart? You may not think...

The science of spring fever

Researchers have confirmed what people have sensed for ages: Our emotions during the springtime can go a little wild. This piece breaks down the impact of the seasonal transition on our bodies and prescribes a few ways to mitigate the effects.

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.

Stress can be contagious—and scientists want to learn more about it

Researchers have shown that being around someone who is stressed can trigger a stress response in your body, such as elevated cortisol levels and elevated heart rate. One way this was recently studied was by having people watch stressful activities, like a recorded job interview or solving challenging math problems, and then sampling hormones in observers' spit.

Why Friday surgeries are (likely) riskier

Scheduling surgery on a Friday may lead to more complications—up to 5% more often—compared to surgeries performed after the weekend. The research was conducted by a team from the United States and Canada and analyzed data from over 450,000 patients who underwent common surgeries in Ontario between 2007 and 2019. Check out their findings here.

Doctors use three key physical markers to determine biological aging

The length of the ends of chromosomes (known as "telomeres"), the gradual change in collections of DNA molecules called "methyl groups", and the secretion of inflammatory proteins are all used as indicators of biological age.

Explore a series of bedtime exercises to improve sleep

Low-impact, mindful movements can potentially help the body and mind relax before sleeping. Such exercises could be a helpful complement to regular exercise during the day.

Doctors weigh in: Are wearable fitness devices useful or just entertainment?

In an age where technology is intertwined with our daily routines, there is an evolving relationship between healthcare professionals and the data gained from our wearable devices. This piece, published on The Verge, explores how doctors view and...

Patients are messaging their doctors online more than ever—recent research suggests portal messages have risen by 157% since 2020.

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

An engineer tracked his moods for decades and helped researchers identify SAD

Civil engineer Herb Kern had bipolar and would record his moods dating back to 1967. He noticed the seasons were a major factor in the increase and severity of his episodes. By reaching out to researchers at the National Institute of Mental Health, Kern became the first human to confirm increased melatonin levels during winter and to receive bright light therapy.