Exercise as it relates to Disease/Physical Activity and Glycemic Control in Adolescents with Type 1 Diabetes

What is the background to this research?
Type 1 Diabetes (T1D), is associated with an autoimmune reaction causing the destruction of pancreatic β-cells, which bars an individual from producing insulin. Currently there is no cure to this disease. There are only systems in place to treat the symptoms of T1D through maintenance of blood glucose levels and injections of insulin. Also through the maintenance of physical health through physical activity.

Patients who have had T1D for a prolonged period display little to no β-cells and regeneration of β-cells is only displayed minimally in infants and young children. T1D is more commonly diagnosed in men and boys.

Hypoglycemia is often seen in patients with diabetes. It consists of periods of abnormally low plasma glucose concentration. Often the symptoms are autonomic, presenting themselves as palpitations, tremors, sweating and hunger. Other symptoms can include altered behaviour, confusion and at its worst, can induce a coma or death. Hypoglycemia can occur immediately after moderate to vigorous physical activity (MVPA) and sometimes between 7-11 hours after activity. This is referred to as a "lag effect" caused by the muscles replenishing glycogen stores.

Physical activity is an important aspect in the management of many chronic diseases not just T1D. In particular to T1D, it has been shown to reduce the risk of further health complications like cardiovascular diseases, improving bone health and maintaining adiposity. In fact, it has been shown by Loprinzi, P. D., et al. (2012), that physical activity has an inverse relationship with adiposity and stress.

Where is the research from?
The research took place over two visits to the Clinical Research Unit of the Institute for Clinical and Translational Science (ICTS) at the University of Iowa (UI). The authors originated from various departments in UI including Health and human physiology, Paediatrics and Biostatistics. Also from the school of sport, exercise and health sciences in Leicestershire, UK. The article was accepted by the American Diabetes Association (ADA) and published in the journal Diabetes Care.

There was an acknowledged duality of interest between an author Michael Tansey being a consultant for a pharmaceutical company, Daiichi Sankyo. Other than this, there were no other conflict of interests reported.

What kind of research was this?
Research for this study conducted by Metcalf, K.M., et al. (2014) was a quantitative, observational study researching the link between T1D and hypoglycemic events spanning the time from overnight to the next day.

Participants chosen for the study were selected in a purposive method, allowing the study to represent a small sub-group in the general population with specific characteristics. These characteristics include all participants diagnosed with T1D, of an average fitness level and whose lifestyles included the MVPA guidelines set by the US department of health and human services.

What did the research involve?
There were a total of 19 participants in the study. The participants were all between 14-20 years old, all were characterised as being of average fitness level and also reached the guidelines of an hour of MVPA in a day.

Participants were required to wear a continuous glucose monitor (CGM) and an accelerometer was worn on the left wrist throughout the period of experiment (3-5 days). During the first visit, participants underwent anthropometric testing, for example, adiposity was determined via displacement plethysmography. Their VO2 max was determined through the use of closed circuit spirometry. The CGM was calibrated to the individuals' blood glucose level on the day and calibrated twice a day in the participants' home.

What were the basic results?
The results show that a session of MVPA participated in during the afternoon to evening period correlated with a higher risk of experiencing a hypoglycemic event. The risk of suffering a hypoglycemic event the next day became 31% more likely to occur with 30 minutes/day of MVPA in the previous afternoon. However there wasn't a significant difference between genders in the likelihood of suffering a hypoglycemic attack in the day after. The risk for overnight hypoglycemia increases to 43% after 30 minutes of MVPA in the afternoon. In this case, there was a significance in gender being that males were more at risk for hypoglycemia overnight after the MVPA.

What conclusions can we take from this research?
MVPA does increase risk of a hypoglycemic event occurring overnight and during the course of the next day. However, it is not recommended to stop performing physical activity. This is because, physical activity, as a whole, is beneficial and also provides a reduction in potential future health complications severity. It even has been shown to increase an individual's sensitivity to insulin.

Practical advice
It is important to note that this article does not in any way discourage an individual from performing exercise. Acknowledges that the benefits outweigh the negatives, of suffering a hypoglycemic event. The benefits being that it reduces the risk of future health complication. For example, the risk of cardiovascular events occurring in the future are reduced. Chiang, J.L., et al (2014) recommend the modification of the recommended daily exercise guidelines of 60 minutes of MVPA daily to something that would suit the individual.

An important issue that needs to be addressed for T1D patients is avoidance of any sort of physical activity out of fear of triggering a hypoglycemic event after exercise. Education of the patient as well as the people interacting with the patient on a day to day basis, can be vital. For example, family members, school nurse, sport coach; should all be educated on T1D and on methods to minimise risks. These risk management option can be done in a number of ways; by keeping a pre-exercise blood glucose level of at least 100 mg/dL  or higher, reducing the basal insulin on the night following exercise and/or simply having snacks that are simple carbohydrate rich easily available.

Current Standards of Medical Care set by the ADA:
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Hypoglycemia and Diabetes by ADA:
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Australian Physical Exercise Guidelines:
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