Exercise as it relates to Disease/Can exercise help children with type 1 diabetes gain control of their overnight glycemic levels?

This is a critique of the original research article by The Diabetes Research in Children Network, DirecNet Study group, Impact of Exercise on Overnight Glycemic Control in Children with Type 1 Diabetes Mellitus submitted to the Journal of Pediatrics in 2005.

This was completed as part of the Health, Disease and Exercise unit at the University of Canberra.

What is the Background to this Research?
Type 1 Diabetes is an autoimmune disorder in which the immune system destroys the insulin producing Beta cells of the pancreas. There is currently no cure and is not preventable with medical or lifestyle changes(1). Type 1 diabetes is one of the most common childhood chronic conditions and represents about 10 percent of all diabetes incidents(1). Type 1 diabetes requires the person to take their own blood glucose levels and administer an insulin injection several times across a day or through the use of an automatic insulin pump(1).

It has been shown that various types of exercise effect a type 1 diabetics blood glucose levels in different ways and at different times. It is shown that resistance exercise continues to effect blood glucose levels for hours after the cessation of exercise and that after aerobic exercise is performed there is a spike in blood glucose levels(2). Therefore, it is important to understand the type of exercise that is being performed and how it will affect Blood glucose levels in order for type 1 diabetics to better control their overnight Glycaemic levels.

Where is the research from?
This study was conducted by The Diabetes Research in Children Network (DirecNet), which is multi-centre study group. The DirecNet network consists of 5 clinical centres and a singular coordinating centre(3). The primary funding resources for DirecNet are the National Institute of Health (NIH) special Type 1 Diabetes Funds and the NICHD. The main objectives of this group are to examine possible risks and preventions of hypoglycaemia in type 1 diabetic children. This study uses the Jaeb centre for health research in Tampa, FL as the coordinating centre for this study(4).

What kind of research was this?
This was a Randomised Control Trial, which is considered to give the best results when looking at a cause-and-effect Relationship(5). Due to the age of the participants the DirecNet group had to get their Consent form and assent form approved by an institutional review board before it was signed by the participants and a Parent or Guardian. The weakness of this trial is that it took place at 5 different centres across America and therefore may have been susceptible to minor changes in the administration of the trial and taking of measurements and results. However, because the trial was run by one overlying group (DirecNet) this would be unlikely as all researchers would have agreed to the same methods(4).

What did the research involve?
The participants for this study had to meet a specific range of variables in order to be eligible to complete the study. These Variables included: Participants were not allowed to participate if they had one of the following; asthma that was medically treated in the previous year, were currently using glucocorticoids or beta blockers, used pseudoephedrine within 48 hours, experienced severe hypoglycaemia (seizure or loss of consciousness) within the previous 2 weeks, an active infection, anticipated a significant change in exercise regimen between admissions, or had another medical condition or were using a medication that in the judgment of the investigator could affect completion of the exercise protocol. The 50 participants completed two overnight stays at a centre, one consisted of a 75minute exercise session in the late afternoon and the other day was the ‘sedentary’ day in which no exercise was completed in the late afternoon. On the Exercise day the participants BGL levels were take at 2 and 3 pm to determine if short-acting insulin or an oral carbohydrate should be administered so that the 4pm/Pre-exercise BGL was between 100 mg/dL and 200 mg/dL (5.5 mmol/L-11.1 mmol/L).
 * Age of 10-18yrs
 * Clinical Diagnosis of Type 1 Diabetes of ≥18 months
 * No changes to their insulin regime for at least 1 Month, involving the use of insulin injections or an insulin pump
 * A HbA1c level of ≤10.0%
 * A BMI in between the 5th and 9th percentile for their age and gender.

The exercise session consisted of 4x15-minute exercise periods with a 5-minute rest in between each session. During the exercise periods the participants walked on a treadmill at a target heart rate of 140bpm. The overnight procedures consisted of dinner at 6:15pm and blood glucose levels taken at 7:00pm, 8:00pm and 9:00pm. The participants were instructed to go to sleep at 10:00pm and utilising an intravenous catheter BGL levels were taken every half hour between 10:00pm and 6:00am. For this study hypoglycaemia was defined as a lab result of ≤60mmg/dL or 3.3 mmol/L.

What were the basic results?
Comparing the results of the exercise night to the sedentary night it is clear that late afternoon exercise can increase the risk of nocturnal hypoglycaemia. 26% of the participants experienced hypoglycaemia on the exercise night as well as 22% who experienced nocturnal hypoglycaemia on both of the nights. The average half hourly BGL indicated that throughout the exercise night BGL levels were around 23mmg/dL (1.265 mmol/L) lower than on the sedentary night.

Going further on the self-reported nights in which the same participants gave information on their physical activity levels and nocturnal glycaemic levels during a normal week. It was found that those who participated in more exercise throughout the week were at an increased risk to nocturnal hypoglycaemia.

What conclusions can we take from this research?
This research shows that a bout of aerobic exercise in the late afternoon does increase your risk of nocturnal Hypoglycaemia. However, given that this research only tests aerobic exercise it is important to consider the different effects that a resistance training program or another different training program may have on overnight glycaemic control. This study does prove that when exercising it is important to consider making changes to overnight insulin regimes as well as food intake. Utilising the weekly report of exercise from this study we can assume the more you exercise during the week that someone partakes in does increase their risk of having more overnight hypoglaecemic incidences.

Practical advice
If you are a Type 1 Diabetic considering starting an exercise program it is important to do some research into the type of exercise you wish to undertake. If you plan on doing exercise in the late afternoon or evening, altering any insulin or food intake to mitigate the risk of nocturnal hypoglycaemia would greatly benefit your well-being. The more exercise that any type 1 diabetic wishes to partake in across the week needs more attention. Nocturnal Hypoglycaemic levels can interrupt sleep and result in feeling unwell if they are reoccurring, in order for a proper recovery post-exercise ensuring good pre and post exercise insulin and eating routines are extremely beneficial to recovery. Before commencing any sort of exercise regime as a Type 1 Diabetic contacting your Endocrinologist or gp for advice on changing your insulin and diet regime to accommodate the exercise.

Further information/resources
General Diabetes Advice: Visit Diabetes Australia, Visit Diabetes America] Resistance exercise versus Aerobic Exercise, Diabetes Care Journal. 2013