Scientists have reported on the association of long sleep with kidney damage in diabetes

In people with type II diabetes, prolonged habitual sleep may be associated with an increased risk of developing or worsening diabetic kidney disease. This conclusion was reached by Japanese researchers who followed 678 patients for about six years. The authors emphasize that the result does not prove that long sleep damages the kidneys, and there is no reason to reduce rest time. What scientists have discovered and why sleep duration may turn out to be an additional signal about the state of health — in the Izvestia article.

What the six-year follow-up showed

The study focused on people with pre-existing type II diabetes. The researchers studied whether the usual sleep duration is associated with the subsequent appearance of diabetic nephropathy or the progression of existing kidney damage. These two outcomes have different meanings. In the first case, we are talking about the development of complications, in the second — about the deterioration of the condition of a person who has already had signs of the disease. The work covered both situations.

Over approximately six years of follow-up, the researchers found a link between longer sleep and an increased risk of these adverse changes. It was especially pronounced in elderly participants and patients with initial signs of kidney damage: microalbuminuria or decreased renal function.

However, this result does not mean that every person with diabetes who sleeps for a long time will necessarily develop nephropathy. Scientists have identified a pattern at the group level. For the prognosis of a particular patient, other information about his health is needed.

Tomoya Mita, an author of the study from the Graduate School of Medicine at Juntendo University in Tokyo, explained that sleep duration can help people notice who need more attention to kidney health.

Why diabetes is dangerous for the kidneys

Diabetic kidney disease, also called diabetic nephropathy, refers to serious complications of diabetes. It can occur with both type I and type II diseases. In the new work, only type II was studied.

The kidneys remove metabolic products and excess water from the blood. Prolonged elevated glucose can damage their blood vessels. High blood pressure, which often accompanies diabetes, can also worsen the damage. These processes usually develop gradually over many years.

According to the Endocrinological Society, diabetic kidney disease affects approximately 30-40% of people with diabetes. Therefore, we are talking about a common complication, not a rare consequence of the disease.

Its significance goes beyond the work of the excretory system. Diabetic kidney damage is associated with an increased risk of cardiovascular events, and with severe progression can lead to kidney failure.

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At the same time, kidney damage does not mean an inevitable transition to the final stage of the disease. According to the US National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK), glucose and blood pressure control helps prevent or slow down damage. Most people with diabetes and kidney disease do not develop kidney failure.

What do early signs of damage mean?

These studies provide information about different aspects of the organ's condition: a urine test shows protein loss, and a blood test helps assess filtration. They are used both to detect the disease and to monitor its course.

In the early stages, kidney disease usually does not cause noticeable symptoms. Therefore, feeling good by itself does not exclude damage, and sleep duration cannot replace laboratory tests. The NIDDK recommends that people with diabetes have their kidneys checked annually.

Long sleep as a possible signal

The main question of the new work is how to understand the discovered connection. Longer sleep may be associated with an unfavorable state of health, but this does not mean that it is the extra hours of rest that cause kidney damage.

In this case, a marker is a sign that may accompany an increased risk. It is not necessarily involved in the development of the disease. For example, the two observed changes may depend on other features of the body's condition.

For this work, this difference is especially significant: some of the participants had signs of kidney damage already at the beginning of the follow-up. It was among such patients that the association with sleep duration was particularly noticeable. This leaves open the question of the role of the initial state of health.

An inverse causal relationship is also possible, in which a deterioration in health affects the need for rest. The study did not establish what exactly happened, but its observational design does not exclude such an explanation. Therefore, the authors suggest considering the duration of sleep as a possible additional clue when evaluating a patient. So far, it is not an independent diagnostic test or a proven cause of nephropathy.

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Why don't the results encourage you to sleep less

A prospective cohort study allows you to track what events occur with the participants over time. In this work, the follow-up lasted about six years, which helped to study the subsequent development and progression of the complication.

However, the researchers did not conduct an experiment in which some patients were assigned a shorter sleep and others a longer one. Consequently, the work did not check whether the risk of kidney damage would change after reducing rest time.

Thus, the rule "the less sleep, the healthier the kidneys" cannot be deduced from the discovered pattern. A separate study is required to assess the benefits or harms of changing the regime. The new data also does not prove that sleep deprivation is safe for people with diabetes.

What questions are still open?

The job report did not specify a specific threshold after which sleep was considered prolonged. Therefore, on its basis, it is impossible to call a certain number of hours dangerous or declare an eight-hour or nine-hour sleep a cause of complications.

The message also does not provide numerical estimates of the risk. The direction of the detected relationship is known from it, but it is impossible to conclude by how many percent the probability of the disease increased and how the absolute indicators differed between the participants.

For further evaluation of the results, sleep measurement methods, criteria for kidney deterioration, and consideration of other health factors are important. The length of rest by itself also does not describe its quality.: these characteristics require a separate study.

Another boundary of conclusions is related to the composition of the participants. The study included Japanese patients with type II diabetes. To what extent the pattern is reproduced in other countries, age groups and in type I diabetes, it remains to be checked separately.

The authors see the results as a reason to study sleep more closely as a possible indicator of vulnerability. The next question is whether information about its duration provides additional benefits compared to the already available information about the age, course of diabetes and kidney condition. The answer to it will help to understand what place this feature can occupy in clinical risk assessment.