2007 Off Campus Research Internship Awardee

Holly Stewart
(Biology and Philosophy Double Major)
(Minor in Latin)



Mentor: Janet Kramschuster, CTRS Diabetic Youth Foundation, Concord, CA.


Diabetics and the Workplace

Holly Stewart

The purpose of this research is to examine the factors in the social environment that are responsible for influencing blood glucose levels in Type 1 Diabetics. This project is in response to discrepancies in the literature about how activity, stress and working environment alter blood glucose levels. The specific focus will be to examine how diabetics respond to the stress and conditions of their working environment, for example, working outside may be just as stressful as working inside, but may involve a different type of physical activity. The literature states that being outside reduces blood glucose levels because activity makes insulin more efficient, yet, there is some difficulty in also accounting for the influence of stress. In this research I would like to examine what types of patterns are present in diabetics and also examine the overall range of blood glucose depending on environmental factors. There may be more complicated circumstances that influence blood glucose than have been recognized in the past.

This project will be executed using three groups: two control groups and one transitional group. One of the control groups will be an indoor group: those diabetics who work mainly indoors but still maintaining and active lifestyle. The second control group will be diabetics that work primarily outside. The assumption is that regardless of whether you work inside or outside there is stress associated with your job, but that over time you are able to compensate for possible stress from the working environment by adjusting insulin levels. Each control group would have a minimum of ten people. The third group is the transitional group. This group would consist of fifteen to twenty diabetics who initially are in an indoor workplace and transition to an outdoor workplace. The transition will be from an indoor workplace to an outdoor diabetes camp. These diabetics will monitor their blood sugars five weeks before going to camp and five weeks through camp. Arguably the stress and demands of being a camp counselor are similar to those of school or an office job.

At the beginning of the experiment standards would be taken in the areas of age, height, weight, amount of insulin (basal levels, bolus ratios), injection method (pump, syringes), type of insulin (long-lasting, short-lasting), years with diabetes, complications, starting glycated hemoglobin (A1C) level, and blood glucose meter type. Participants in the study would be expected to test blood glucose levels at 12am, 2am (if awake), 8am, 12pm, 3pm, 6pm and 9pm (± no more than one hour). A1C blood draws will occur for the controls at the beginning and end of the study and for the transitional group at the beginning, half-way and at the end of the study. In weeks 2, 6, and 10, the participants in the transitional group will be required to do basal checks of their insulin levels over a period of one week, checking in four hour blocks of time. Participants will be required to document their blood glucose, note activity (time and location), when insulin given and any changes to their routine. The goal is to look for not only changes in blood glucose numbers in general, but also look at the range of blood glucose, the percentage of high and low blood glucose and how that changes.


An Analysis of Blood Glucose Patterns and Effects on Blood Glucose Values
and Glycated Hemoglobin Levels in Type 1 Diabetics due to
Changes in the Level of Activity in the Work Environment

By Holly L. Stewart, Bryn Mawr College;

Mentored by Janet Kramschuster, CTRS, Diabetic Youth Foundation

Objectives: The goal of this experiment was to understand the effect on blood glucose from changes in the level of activity in the work environment in Type 1 Diabetics; and to identify patterns in blood glucose which result from these changes in activity.

Diabetes mellitus: Type 1 is an autoimmune disease affecting the beta cells of the pancreas, rendering them unable to produce insulin which is needed in order to metabolically process glucose. The regulation of blood glucose levels is complex and not yet well understood. However, it is well know exercise has positive effects on blood glucose control by creating greater insulin sensitivity. Previous research has identified that an increase in activity for Type 1 Diabetics leads to better metabolic control and lipid profile. Despite the positive effects of exercise on blood glucose control however, the specific effects of exercise on insulin sensitivity are not well understood and tend to be extremely variant depending on the individual. This inconsistency in being unable to predict how blood glucose levels fluctuate due to changing levels of activity makes it difficult to maintain target range of blood glucose levels between 80 and 150 mg/dl. Because of this individual variation, little research has been designated toward attempting to find commonalities and patterns for Diabetics, since many factors (including exercise, stress and food) can account for changes in blood glucose levels.

This research was aimed to explore the effect of exercise on blood sugar and investigate whether consistent blood glucose patterns existed among diabetics with very different self-management philosophies. This research attempted to primarily examine the overall as well as the daily patterns of blood glucose values, with a secondary focus on examining the psychological impacts which result from such a study. It was apparent that an increase in exercise itself had a significant yet extremely complex effect on the regulation of blood glucose values. Additionally the psychological effects of logging blood glucose values provided inspiration for further research as well as further examination of the medical strategies presented to young-adult Type 1 Diabetics today.

Over a twelve week period this research examined the patterns of blood glucose in three groups of Type 1 Diabetics, ages 18 to 30, distinguished by their levels of activity. There were two control groups, one sedentary (less than 3 hours of activity per week) group and one active (more than 6 hours per week of intensive activity) group. The third group was composed of fourteen diabetics who were in a transitory state of activity. Having monitored this group for two to four weeks in a sedentary lifestyle they were than placed in an environment where their activity increased to over eight hours per day. The changes in blood glucose patterns, insulin sensitivity and glycated hemoglobin (hA1C, A1C) levels were monitored for the remainder of the study.

Those individuals in the transitory group were required to check their blood glucose levels a minimum of six times per day, including prior to meals. In addition to checking blood glucose levels, participants were required to keep a log of their blood glucose levels and carbohydrate intake, noting any changes in insulin dosages due to activity. Glycated hemoglobin levels were taken during Week One, Week Five and Six, and Week Ten of the research. Surveys were conducted at the beginning and the end of the study to evaluate the effects on logging blood glucose as well as discussing the changes in insulin sensitivity and control due to the change in activity.

Final A1C values taken at Week Ten demonstrated a significant decrease (p<0.01) as compared with initial A1C values taken during Week One (Figure 1)

Figure 1: Comparison of A1C values at Week 1, Weeks 5 and 6, and Week 10 (n=14). Data is represented as mean values ± SEM.

Two distinct patterns regarding blood glucose were discovered in the data for the transition week to a more active environment. During the transition week blood glucose readings for Days 2-5 revealed a significant (p<0.01) pattern of hypoglycemia (Figure 2).


Figure 2: Pattern of blood glucose values (mg/dl) for days 1-6 during transition week. Data reports average values at 12am and 12pm. Box indicates significant pattern of hypoglycemia (n=5).

The second distinct pattern demonstrated extreme fluctuations in blood glucose values. This pattern of fluctuation was only apparent in Days 4-9 and no other block of time showed significant changes in blood glucose values (Figure 3).


Figure 3: Pattern of blood glucose values (mg/dl) for Days 4-9 of the transition week. Data points represent blood glucose readings at 12am, 8am, 12pm and 6pm, respectively. (n=6)

Over the course of the study, there was a significant (p< 0.01) increase in hypoglycemic blood glucose values between the hours of 10pm and 6am (Table 1).


Percent Night    Lows
































Table 1: Comparison of percentage of hypoglycemia readings between 10pm and 6am (n=14). *Indicates transition week.

Discussion and Conclusions:

The results from this research illustrate that an increase in activity has a diverse and significant effect on blood glucose levels in Type 1 Diabetics. An overall decrease in A1C levels suggests that regular physical activity over an extended period of time is an effective way to lower glycated hemoglobin levels. This control over blood glucose values is extremely important for avoiding the late-onset complications of uncontrolled diabetes; however it is still unclear just how exercise alone improves the chances of avoiding such complications. The decrease in average A1C levels over the course of the ten weeks also may be due to the impact of logging blood glucose values and having regular A1C readings. This conclusion is supported by the literature produced by Farmer, AJ et al. who found that consistent and “real-time” feedback of information about blood glucose levels significantly improved glycemic control. Although the daily effects of exercise may be complicated, the overall trend of a higher percentage of target range numbers (as demonstrated by lower A1C levels) due to an increase in activity is an important factor in control of Type 1 Diabetes.

The two blood glucose patterns identified were helpful to better understand the ways in which an increase in activity can affect blood glucose values. Although not every individual’s data followed these patterns, it was encouraging to find that there are basic patterns of blood glucose change which may occur in correlation with an increase in physical activity. Virtually no literature exists describing the existence of such patterns in Type 1 Diabetics, simply because the research is complicated and the results are inconsistent. The specific trends of intense low blood glucose readings from Days 2-5 of the transition week may be complicated by such factors as stress and adrenaline. Further research would need to be done to better understand the body’s response to such an immediate and drastic increase in exercise, and this trend may simply be representative of the body’s response to such an increase. The second pattern found demonstrating extreme fluctuations is interesting because this is indicating the body may be struggling to adapt and an increase in insulin sensitivity may take time. Further research would need to investigate the time it takes for the body’s sensitivity to insulin to increase and further control would be needed on such other factors such as stress and carbohydrate intake.

The significant increase in the amount of nighttime hypoglycemic blood glucose levels supports what is found in the literature. McMahon SK, et al. found moderate-intensity afternoon exercise created a delayed risk for nighttime hypoglycemia. Participants responded to these nighttime hypoglycemic episodes by decreasing their overall daily intake of insulin. Over the course of the study each participant’s sensitivity to insulin increased. The change in sensitivity varied, ranging from a one-third to three-quarters reduction in daily totals of insulin at the end of the study as compared with the beginning. Since exercise make insulin more efficient it is consistent to conclude that an increase in physical activity is responsible for this change. It would be interesting to have a follow-up study to examine as participants’ lifestyles changed back into more sedentary settings whether insulin sensitivity remained the same and if it changed, it would be interesting to investigate how long it took for this change to occur.

One of the most interesting aspects of this research was the psychological effects as demonstrated through subjective surveys at the beginning and end of the research period. Participants reported a change in the way they thought about their blood glucose values, reporting at the end of the study they were much more conscious about how they felt when they were hyper- or hypoglycemic. It was also interesting to hear participants discuss the effects of logging their blood glucose values. All the participants reported a change in attitude toward their blood glucose readings which they self-reported as being because they were logging their values and were better able to see trends in their numbers. The act of writing it down for a number of the participants became a motivator for attempting to remain in tighter control and checking blood glucose values more often. This psychological aspect of recording blood glucose levels could significantly impact the way Type 1 Diabetics manage their Diabetes. Further research would be necessary to confirm that logging blood glucose values not only has a psychological impact but furthermore encourage better blood glucose control, however this research has served as a jumping point for further research into this area.

Realistically there are a number of factors which could not be controlled for in this experiment. Stress and the effect of stress on blood glucose values is something which cannot easily be accounted for. It is also pertinent to note that the transition group was isolated to one location at a summer camp for diabetics and the psychological effects of being in an environment surrounded by the support of other Type 1 Diabetics was not accounted for either. Food and carbohydrate intake was not controlled and some variations in blood glucose levels could have been due to changes in food or the type of food being consumed at any given meal. Despite all of these potential sources of complication, this research demonstrates the varying and complex effects of exercise on blood glucose levels and prompts further research into other factors in the environment which may affect blood glucose values also.


World Health Organization Department of Noncommunicable Disease Surveillance (1999). Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications.

Rybka J. “Development of opinions on physical exercise for diabetics.” 

Valerio G, Spagnuolo MI, Lombardi F, Spadaro R, Siano M, Franzese A. “"Physical activity and sports participation in children and adolescents with type 1 diabetes mellitus."

Schneider S, Iannotti RJ, Nansel TR, Haynie DL, Simons-Morton B, Sobel DO, Zeitzoff L, Clark L, Plotnick LP. "Identification of distinct self-management styles of adolescents with type 1 diabetes."

Salvatoni A, Cardani R, Biasoli R, Salmaso M, De Paoli A, Nespoli L. “Physical activity and diabetes.

Farmer AJ, Gibson OJ, Dudley C, Bryden K, Hayton PM, Tarassenko L, Neil A. “"A randomized controlled trial of the effect of real-time telemedicine support on glycemic control in young adults with type 1 diabetes."

McMahon SK, Ferreira LD, Ratnam N, Davey RJ, Youngs LM, Davis EA, Fournier PA, Jones TW. “"Glucose requirements to maintain euglycemia after moderate-intensity afternoon exercise in adolescents with type 1 diabetes are increased in a biphasic manner."

My deepest thanks to Janet Kramschuster and Bearskin Meadow Camp for all their help this summer in this research.

Thanks also to the John Muir Medical Network and to Dr. Mary Simon, in her help and guidance in understanding Diabetes and the endocrine system.

Thanks also to Bryn Mawr College and for all the friends, family, nurses and staff who made this research interesting and possible.


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