Accelerometer Use in the Prevention of Exercise-Associated Hypoglycemia in Type 1 Diabetes: Outpatient Exercise Protocol
Condition: Type 1 Diabetes
MeSH terms: Diabetes Mellitus; Diabetes Mellitus, Type 1; Hypoglycemia
Study type: Interventional

Summary: 
      Manually suspending an insulin pump at the beginning of aerobic exercise reduces the risk of
      exercise-associated hypoglycemia (low blood sugar) in patients with type 1 diabetes (T1D).
      However, since patients with T1D often do not make exercise-related adjustments to their
      insulin regimen, our group has developed an algorithm to initiate pump suspension in a
      user-independent manner upon projecting exercise-associated hypoglycemia. The current study
      seeks to test the efficacy of this algorithm by asking users to participate in a sports camp
      while wearing an insulin pump, continuous glucose monitor, and accelerometer/heart rate
      monitor (to detect exercise), which will communicate electronically to a pump shutoff
      algorithm. On one of the days the algorithm will be used, while on the other day their normal
      insulin rate will continue for comparative purposes.

      The investigators hypothesize that the use of an accelerometer-augmented computer algorithm
      for insulin pump suspension during exercise will result in significantly fewer episodes of
      hypoglycemia (both during exercise and in post-exercise monitoring) than in exercise without
      a pump suspension algorithm.
    

Detailed description: 
      Regular aerobic exercise confers a plethora of health benefits to all individuals and is
      considered an essential component of the management of type 1 diabetes (T1D) [1]. However, in
      contrast to non-diabetic subjects - in whom the increased muscle energy requirement during
      exercise leads to suppression of endogenous insulin secretion - patients with T1D are
      dependent upon exogenous insulin and are thus at risk for exercise-associated hypoglycemia
      [1]. Exercise-associated hypoglycemia is the most frequently reported adverse event related
      to exercise in diabetes [2] and hypoglycemia can occur during exercise or several hours
      afterwards [3,4]. Although previous research has shown that pre-meal dose reduction of
      subcutaneous insulin can be effective at decreasing the incidence of exercise-associated
      hypoglycemia [5], patients with T1D often do not perform such adjustments [6,7].

      In contrast to subcutaneous insulin injections, which are reliant upon the patient or
      caretaker to determine dosage, the insulin pump provides a unique opportunity to avoid
      hypoglycemia via user-independent, computer-based algorithms for determining insulin
      delivery. Previous research conducted here at Stanford has demonstrated that algorithms based
      on continuous glucose monitor (CGM) data can prevent hypoglycemia in the sedentary setting by
      inducing insulin pump suspension [8-10]. In addition, a study of children and adolescents
      conducted at Stanford (as a center in the DirecNet group) demonstrated that suspending an
      insulin pump at the beginning of a period of moderate aerobic exercise reduces the risk of
      hypoglycemia during that exercise period and subsequently overnight [11]. Thus, by utilizing
      exercise-detecting accelerometers and an algorithm to initiate pump suspension during
      exercise, it is likely possible that people with diabetes could avoid exercise-associated
      hypoglycemia even if they failed to manually alter their pump settings. However, to date, no
      published studies have utilized accelerometer-derived data in an insulin pump suspension
      algorithm during exercise.

      Accelerometers are light-weight motion-sensing devices that can be worn to provide
      information about the intensity and duration of physical activity [12]. They are small,
      inexpensive, and could easily be incorporated into current sensors and "patch" pumps. They
      can also be used independently or combined with a heart rate monitor (HRM) [13], although
      most commercially available HRMs currently require a chest strap that can be uncomfortable to
      wear. Previous studies evaluating the effect of physical activity on insulin sensitivity have
      utilized accelerometers (worn on a belt at the small of the back, the right side of the trunk
      in the mid-axillary line, or the left side of the chest) with and without HRMs for activity
      recognition during subjects' everyday lives. These data were used to classify activity as
      sedentary, light, moderate, or vigorous based on acceleration signal counts measured over
      one-minute intervals [13-17]. One study investigated four different accelerometers in a
      clinical research setting and found each to be very accurate in assessing the intensity of
      physical activity, regardless of subjects' body habitus [18]. Thus, these devices can provide
      a reliable means by which the onset, duration, and intensity of exercise can be recognized
      and reported in real-time to the other components of an artificial pancreas. When combined
      with CGM and insulin delivery data, this exercise information is a valuable tool in designing
      an algorithm to decrease or stop insulin delivery in order to decrease the risk of
      exercise-associated hypoglycemia.

      In the first phase of this study (in press), 22 subjects with type 1 diabetes went about
      their everyday lives while wearing an insulin pump, CGM, and accelerometer/heart rate
      monitor. After the monitoring period, the devices were downloaded and the data were used to
      augment an existing predictive low glucose suspend (PLGS) algorithm to incorporate activity.
      In a computer simulator, the PLGS algorithm reduced hypoglycemia by 64%, compared to 73% and
      76% reductions for the accelerometer-augmented and HRM-augmented algorithms, respectively.

      In the next phase of this study, we seek to test the newly developed algorithm in a real-life
      setting in the form of a structured sports (soccer) camp to further see if modifications to
      the algorithm are required.
    

Intervention name(s): Computer algorithm to initiate pump suspension
Intervention type(s): Device
Intervention description(s): If the computer algorithm senses impending risk for hypoglycemia it sends an alert to an on-site physician to recommend a manual suspension of the subject's insulin pump
Other intervention name(s): Augmented predictive low glucose suspend algorithm
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: randomized crossover design. Subjects with type 1 diabetes participated in a structured soccer session on two separate dates at least one week apart. During one session a subject's basal insulin rate was continued ("off-algorithm"), while during the other session the algorithm (see "algorithm monitoring" below) was in effect ("on-algorithm"); the order of on- versus off-algorithm was chosen at random. The rate of hypoglycemia during exercise were compared between each group.
Hypoglycemia was defined as (1) any meter blood glu
cose (BG) reading of =60 mg/dl, (2) two consecutive meter
BG readings =70 mg/dl done within one hour, or (3) any instance in which carbohydrates were given at a subject's request for symptoms of hypoglycemia (regardless of corre sponding meter BG reading).
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Type 1 diabetes; Hypoglycemia; Accelerometer