You might feel groggy and need days to get adjusted to the switch from standard time to daylight saving time or vice versa. That’s an example of what happens when your circadian rhythm is disrupted.
Your body works on a 24-hour cycle, coinciding with changes from day to night, light to dark. Anything that interferes with this cycle can disturb your sleep and alertness and, importantly, put your health in jeopardy. In a recent scientific statement, the American Heart Association (AHA) emphasizes the importance of regulating your circadian rhythm to lower your risks of cardiometabolic disease and several factors that contribute to it.
“The circadian system drives the alignment with your light-dark cycle—light being when you’re awake and dark when you normally would be sleeping,” explains Nancy Foldvary-Schaefer, DO, with Cleveland Clinic’s Sleep Disorders Center. “If the circadian system cannot effectively align with the light-dark cycle, you’re at risk for a variety of negative health outcomes.”
Fortunately, you can correct circadian disruption, put your mind and body back “on the clock” and avoid these health risks.
What Is Circadian Rhythm?
Your circadian system operates on a series of 24-hour rhythms, or internal clocks. The central clock is an area of the brain known as the suprachiasmatic nucleus (SCN), which receives information about light and dark and sends signals to other areas of the brain that regulate hormones, body temperature, metabolism and other functions that govern your alertness and sleepiness. This clock drives other clocks affecting the heart, digestive system, kidneys and other organs.
When it’s daytime, the SCN, influenced by light exposure, produces signals that keep you alert—which is why people who work night shifts may find it difficult to sleep during the day—and it decreases them in the hours leading up to bedtime.
Timing when you sleep and wake up and maintaining a consistent sleep-wake cycle are critical for maintaining your circadian rhythm. Problems can occur when the cycle is disturbed by factors like shift work, jet lag, time changes, sleep disorders like insomnia or delayed sleep phase syndrome (in which your normal sleep and wake times are at least two hours later than usual), abnormal eating or exercise times or simply deviating from your normal weekday sleep schedule by sleeping in on weekends.
“Timing is a big part of this, but independent of the timing, the circadian system has to have this regularity, this rhythm to it,” Dr. Foldvary-Schaefer says. “When sleep is not timed well and consistently, when we eat in the middle of the night instead of during the day or exercise at 10 p.m. instead of 10 a.m., that can undermine your circadian system’s natural, innate ability to keep your body and brain aligned with the light-dark cycle.”
Circadian Disruption Woes
Some evidence suggests that persistent night-shift work that causes circadian disruption is linked to increased risks of prostate cancer in men and breast cancer in women. Shift workers also tend to weigh more than non-shift workers and are at higher risk for type 2 diabetes, hypertension and metabolic syndrome, Dr. Foldvary-Schaefer says.
But you don’t have to be a shift worker to suffer the consequences of circadian disruption. As more people have become increasingly exposed to artificial light at night (from electronic devices and other sources), pushed their eating times later and maintained irregular work and activity schedules, circadian health has deteriorated and, along with it, certain health parameters, Dr. Foldvary-Schaefer says.
“Over decades, you see this gradual nipping away at sleep duration and the emergence of this 24/7 kind of society that we live in,” she says. “People have become voluntarily sleep-deprived, and that leads to a host of issues that feed into circadian misalignment. As we’ve slept less, we’ve gained more weight, and then you have these epidemics of obesity and short sleep duration. That is a massive public health challenge.”
In its recent scientific statement, the AHA notes that circadian disruption can increase the risk of not only weight gain, but inflammation, type 2 diabetes, hypertension, coronary artery disease, cerebrovascular disease, heart attack, and heart failure (Circulation, Nov. 25, 2025). For example, your blood pressure typically dips overnight, but circadian disruption can interfere with this process, leading to non-dipping blood pressure patterns that have been linked with increased cardiovascular risk.
Plus, in a recent study of 466 people (median age 55), researchers reported that the participants with greater levels of exposure to artificial light at night (a chief contributor to circadian rhythm problems) had higher levels of stress-related neural activity in the brain, increased arterial inflammation, and a greater risk of cardiovascular disease over five- and 10-year periods (AHA Scientific Sessions, November 2025).
How to Reset Circadian Rhythm
If your circadian cycle is out of rhythm, talk to your doctor about melatonin supplements. “Melatonin, appropriately timed and taken, can help with jet lag and delayed sleep phase syndrome, but there’s much less evidence that it helps with insomnia, and most people are taking it because they are having trouble falling asleep,” Dr. Foldvary-Schaefer cautions. “When we do recommend it, we suggest it be used in very small doses, 1 milligram or less, taken two to four hours before bedtime.”
More importantly, work to re-establish consistent timing of your eating, exercising, sleep, and, especially, light exposure. (See “Get on the Clock.”)
“It’s so important to make sure the rhythms in your brain and body are optimally synchronized,” Dr. Foldvary-Schaefer says. “Sunlight is the strongest form of light and the primary synchronizer, so if you’re living in your basement or going from your office to a dark bedroom, you’re depriving your body and brain of natural light exposure that’s so critically important for health. So, use the sunshine.”
