Scientists have reported on the connection of biorhythms with sugar control in diabetes

In people with type II diabetes, more stable circadian rhythms are associated with better blood sugar control, and physical activity in the afternoon is associated with lower glucose fluctuations. These conclusions were reached by researchers who compared data from sugar sensors and fitness bracelets in 122 patients who received insulin. Why not only the amount of movement, but also its time may be important for metabolism, what the study showed and what questions remain unanswered so far — in the Izvestia article.

Why does the body have its own schedule?

With type II diabetes, nutrition, exercise, and medications are usually discussed. However, all this happens at a certain time: a person eats breakfast, goes to work, spends several hours sitting, has dinner and goes to bed. Such a schedule is important for the body.

Circadian rhythms are called rhythms that repeat approximately every 24 hours. They are involved in regulating sleep, hormone release, appetite, and digestion. According to the US National Institute of General Medical Sciences, almost all organs and tissues have their own circadian rhythms. Their work is coordinated by the main biological "clock mechanism" in the brain, which receives information about light and dark. Rhythms are also influenced by nutrition and physical activity.

The connection with sugar is explained by the peculiarities of metabolism. Glucose serves as a source of energy, and the hormone insulin helps it flow from the blood into the cells. In type II diabetes, the body does not use insulin efficiently enough or does not produce enough of it. As a result, blood glucose levels rise.

At the same time, the body's ability to cope with incoming glucose varies throughout the day. In a laboratory paper published in PNAS in 2015, 14 healthy volunteers underwent two routines: normal and with a 12-hour sleep-wake cycle shift. The researchers used the same test meals. On a biological evening, the body did a worse job with glucose than on a biological morning; misalignment of the internal clock with the schedule further worsened the indicators. This study helped to show that the internal phase of the day is also important. But its results cannot be automatically transferred to all people with diabetes.

How was the pulse compared with sugar levels?

In the Korean work, the researchers focused on people with already diagnosed type II diabetes. They studied the data of 122 Ansan Hospital patients who received insulin therapy in 2021-2024. Each participant simultaneously wore a continuous glucose monitoring system and a fitness bracelet for ten days.

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The devices made it possible to compare sugar changes, sleep duration, number of steps, and heart rate. The scientific abstract clarifies that Dexcom G6 sensors and Fitbit Inspire 2 bracelets were used. The parameters of the circadian rhythm were calculated based on pulse data: the severity of its fluctuations and compliance with the daily model were evaluated. Therefore, the stability of the rhythm in this work cannot be reduced only to the habit of going to bed at the same time.

This approach makes it possible to consider everyday life and glucose fluctuations together. Instead of a separate sugar indicator, researchers get a sequence of measurements and can check how it relates to movement and sleep.

Why is medium sugar not enough

An important part of the work is the assessment of not only the total glucose level, but also its fluctuations. For a person with diabetes, both directions of deviation are important: sugar may be too high, and during treatment, it may drop too low. This decrease is called hypoglycemia.

Glycated hemoglobin helps to estimate the average glucose level over the previous months. But the average value does not reflect the whole picture: two patients with a similar HbA1c result may have different frequency and severity of sugar rises and falls. Continuous monitoring allows you to see these changes, including at night.

One of the indicators of such monitoring is the time in the target range. It shows how much of the observation the glucose level remained within the set limits. For many adults with diabetes, the guideline is 3.9–10 mmol/L, or 70-180 mg/dl. The general goal for most patients is to spend more than 70% of their time in this range, but the doctor can set other guidelines based on the person's condition. The time is estimated separately below and above the range.

Therefore, a favorable result does not just mean lower sugar. What matters is whether it is possible to keep it within suitable limits without frequent episodes of dangerous decline.

Sleep is associated with both an increase and a decrease in glucose

Another connection was about sleep. In a Korean study, longer sleep was associated with shorter time spent at low glucose levels and lower sugar fluctuations.

This observation does not mean that the longer you sleep, the better the result will be. It does not establish the optimal sleep duration for each patient and does not prove that an additional hour of rest will prevent hypoglycemia.

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The broader scientific context shows why sleep quality deserves attention. According to the materials of the National Institute of Diabetes, Digestive and Kidney Diseases of the USA, insufficient and irregular sleep is associated with a decrease in insulin sensitivity.

In addition, people with diabetes have obstructive sleep apnea, a condition in which breathing is intermittently interrupted during sleep. It can also complicate glucose control. Therefore, persistent sleep problems should be discussed with a doctor as part of the overall picture of the disease.

What the study has not yet proved

The authors designate the work as a preliminary observational analysis. They identified links between rhythm characteristics, activity, and glucose, but did not test treatment by changing the schedule.

This leaves open the question of the direction of communication. For example, a more prosperous state can help a person sleep better and move more. Taking into account individual factors increases the reliability of the analysis, but does not exclude all possible explanations.

There are also limitations on the scale. The study involved patients from the same hospital, all of whom received insulin, and each was monitored for 10 days. This data cannot be extended to people with type I diabetes, all patients with type II diabetes, or people without diabetes without additional verification.

How the results can be useful in practice

The practical significance of the work so far lies in expanding the issues that can be discussed at the reception. In addition to nutrition and medications, it may be useful for the doctor to know when the patient sleeps, works and moves, whether he has night shifts and how much the schedule changes. A sleep and activity diary along with glucose measurements can help make this conversation more specific.

Special attention is required for people receiving insulin. Increasing exercise can reduce glucose not only during exercise, but also after it. According to NIDDK, the effect of unusually high activity can persist for up to 24 hours. Therefore, changes in exercise should be coordinated with the attending physician, taking into account nutrition, medications and sugar control. According to the results of this work, it is impossible to independently change the dose of insulin.

The Korean team's next step should be a lifestyle intervention study. The scientists intend to test whether actual glucose control will improve if patients are helped to adjust their circadian rhythms. They also plan to study the relationship of biorhythms with diabetic kidney damage and retinopathy, a complication of the retina.