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Biomedical subjects

L A Gonder-Frederick

Publications and source records attributed to L A Gonder-Frederick.

At least 19 recordsLinked to original sources
PubMed1997

Symmetrization of the blood glucose measurement scale and its applications.

OBJECTIVE: To introduce a data transformation that enhances the power of blood glucose data analyses. RESEARCH DESIGN AND METHODS: In the standard blood glucose scale, hypoglycemia (blood glucose, < 3.9 mmol/l) and hyperglycemia (blood glucose, > 10 mmol/l) have very different ranges, and euglycemia is not central in the entire blood glucose range (1.1-33.3 mmol/l). Consequently, the scale is not symmetric and its clinical center (blood glucose, 6-7 mmol/l) is distant from its numerical center (blood glucose, 17 mmol/l). As a result, when blood glucose readings are analyzed, the assumptions of many parametric statistics are routinely violated. We propose a logarithmic data transformation that matches the clinical and numerical center of the blood glucose scale, thus making the transformed data symmetric. RESULTS: The transformation normalized 203 out of 205 data samples containing 13,584 blood glucose readings of 127 type 1 diabetic individuals. An example illustrates that the mean and standard deviation based on transformed, rather than on raw, data better described subject's blood glucose distribution. Based on transformed data: 1) the low blood glucose index predicted the occurrence of severe hypoglycemia, while the raw blood glucose data (and glycosylated hemoglobin levels) did not; 2) the high blood glucose index correlated with the subjects' glycosylated hemoglobin (r = 0.63, P < 0.001); and 3) the low plus high blood glucose index was more sensitive than the raw data to a treatment (blood glucose awareness training) designed to reduce the range of blood glucose fluctuations. CONCLUSIONS: Using symmetrized, instead of raw, blood glucose data strengthens the existing data analysis procedures and allows for the development of new statistical techniques. It is proposed that raw blood glucose data should be routinely transformed to a symmetric distribution before using parametric statistics.

Adult↗
PubMed1995

Reduced awareness of hypoglycemia in adults with IDDM. A prospective study of hypoglycemic frequency and associated symptoms.

OBJECTIVE: To prospectively evaluate the frequency and severity of hypoglycemic episodes in IDDM subjects who declare themselves to have reduced awareness of hypoglycemia, to validate their self-designations in their natural environment, and to determine objectively the presence or absence of autonomic and neuroglycopenic symptoms associated with their low blood glucose (BG) levels. RESEARCH DESIGN AND METHODS: A total of 78 insulin-dependent diabetes mellitus (IDDM) subjects (mean age 38.3 +/- 9.2 years; duration of diabetes 19.3 +/- 10.4 years) completed two sets of assessments separated by 6 months. The assessments included reports of frequency and severity of low BG, symptoms associated with low BG, and a BG symptom/estimation trial using a hand-held computer (HHC). Diaries of hypoglycemic episodes were kept for the intervening 6 months. HbA1 levels were determined at each assessment. RESULTS: Of the subjects, 39 declared themselves as having reduced awareness of hypoglycemia (reduced-awareness subjects). There were no differences between these reduced-awareness subjects and aware subjects with regard to age, sex, disease duration, insulin dose, or HbA1. During the HHC trials, reduced-awareness subjects were significantly less accurate in detecting BG < 3.9 mmol/l (33.2 +/- 47 vs. 47.6 +/- 50% detection, P = 0.001) and had significantly fewer autonomic (0.41 +/- 0.82 vs. 1.08 +/- 1.22, P = 0.006, reduced-awareness vs. aware) and neuroglycopenic (0.44 +/- 0.85 vs. 1.18 +/- 1.32, P = 0.004, reduced-awareness vs. aware) symptoms per subject. Prospective diary records revealed that reduced-awareness subjects experienced more moderate (351 vs. 238, P = 0.026) and severe (50 vs. 17, P = 0.0062) hypoglycemic events. The second assessment results were similar to the first and verified the reliability of the data. CONCLUSIONS: IDDM subjects who believe they have reduced awareness of hypoglycemia are generally correct. They have a history of more moderate and severe hypoglycemia, are less accurate at detecting BG < 3.9 mmol/l, and prospectively experience more moderate and severe hypoglycemia than do aware subjects. Neither disease duration nor level of glucose control explains their reduced awareness of hypoglycemia. Reduced-awareness individuals may benefit from interventions designed to teach them to recognize all of their potential early warning symptoms.

Adult↗
PubMed1994

Frequency of severe hypoglycemia in insulin-dependent diabetes mellitus can be predicted from self-monitoring blood glucose data.

Severe hypoglycemia is associated with insulin-dependent diabetes mellitus and may occur more frequently as metabolic control approaches normal. The goal of this study was to determine whether the frequency of severe hypoglycemia could be predicted by the following predictor variables: 1) frequency and degree of low blood glucose (BG) readings, 2) degree of BG variability during routine self-monitoring blood glucose (SMBG) readings, and 3) level of glycemic control measured by glycosylated hemoglobin-A1 (HbA1). Seventy-eight insulin-dependent diabetes mellitus subjects from 3 different sites had their glycosylated HbA1 assayed and then performed 50 SMBG recordings during the next 2-3 weeks. Over the following 6 months, subjects recorded their severe hypoglycemic episodes (stupor or unconsciousness). There was no difference in the number of severe hypoglycemic episodes between subjects in good vs. poor metabolic control. A higher frequency of severe hypoglycemia during the subsequent 6 months was predicted by frequent and extreme low SMBG readings and variability in day to day SMBG readings. Regression analysis indicated that 44% of the variance in severe hypoglycemic episodes could be accounted for by initial measures of BG variance and the extent of low BG readings. Patients who recorded variable and frequent very low BG readings during routine SMBG were at higher risk for subsequent severe hypoglycemia. Individuals who had lower glycosylated Hb levels were not at higher risk of severe hypoglycemic episodes.

Adult↗
PubMed1994

Individual differences in neurobehavioral disruption during mild and moderate hypoglycemia in adults with IDDM.

This study investigated the neurobehavioral effects of mild and moderate hypoglycemia in adults with insulin-dependent diabetes mellitus (IDDM). On 2 consecutive days, 26 subjects were tested in a counterbalanced, randomized, single-blind, crossover design. On the experimental day, subjects performed tests at 6.4, 3.6, and 2.6 mmol/l and again after glycemic recovery to 6.3 mmol/l. On the control day, subjects performed tests four times at euglycemia. Three months after testing, 15 subjects repeated the experimental day protocol. Results demonstrated that both mild and moderate hypoglycemia significantly disrupted performance. However, performance deterioration varied substantially across individual subjects. Men exhibited significantly more deterioration than women at mild hypoglycemia, and subjects with a history of unconsciousness due to hypoglycemia exhibited more deterioration than subjects with no such history. Individual deterioration scores during repeat testing significantly correlated with performance during original testing. Recovery from hypoglycemia-related impairment varied across individuals and was correlated with degree of impairment during hypoglycemia. These results suggest that the glycemic threshold for onset and recovery from neurobehavioral deterioration with hypoglycemia, as well as degree of impairment experienced, varies across individuals. Furthermore, these individual differences are stable across time.

Adult↗
PubMed1993

Disruptive effects of acute hypoglycemia on speed of cognitive and motor performance.

OBJECTIVE: To directly examine whether hypoglycemia differentially slows cognitive versus motor function, to evaluate the reliability of hypoglycemic-related slowing, and to examine factors contributing to individual differences. RESEARCH DESIGN AND METHODS: IDDM subjects (n = 10) were administered a pure cognitive and a pure motor neuropsychological test at euglycemia (5.4 mmol), blood glucose nadir (2.6 mmol), postnadir (3.6 mmol), and again at euglycemia (6.7 mmol). To assess the practice effect, matched control subjects were tested at similar time intervals. RESULTS: Concurrent and test-retest reliability for all tests was robust (r = 0.68-0.94). Only cognitive tasks demonstrated impairment at nadir (P < 0.04). Individual differences, in terms of cognitive impairment, were significantly correlated with levels of blood glucose at nadir and baseline performance. CONCLUSIONS: Cognitive tasks appear to be more sensitive to neuroglycopenia than motor tasks. Cognitive impairment caused by hypoglycemia is reliable and differs across subjects. Individuals who show reliable sensitivity to cognitive impairments of hypoglycemia should avoid moderately low blood glucose levels.

Adult↗
PubMed1991

Multifactorial origin of hypoglycemic symptom unawareness in IDDM. Association with defective glucose counterregulation and better glycemic control.

To assess potential relationships between unawareness of hypoglycemic symptoms and both defective glucose counterregulation and therapy-associated altered glycemic thresholds, symptoms and hormonal responses to hypoglycemia were quantitated during standardized insulin infusion tests in 41 patients with insulin-dependent diabetes mellitus (IDDM). The glycemic thresholds for both neurogenic and neuroglycopenic symptoms (and those for both epinephrine and pancreatic polypeptide release) were at lower plasma glucose concentrations in both patients with defective (n = 9, 22%) and those with adequate glucose counterregulation and, among the latter, in patients with lower compared with higher glycosylated hemoglobin levels. The data are consistent with the concept that both defective glucose counterregulation and improved glycemic control contribute to excessive hypoglycemia in IDDM by reducing awareness of symptoms of developing hypoglycemia and by impairing physiological defenses against hypoglycemia. Thus, hypoglycemic symptom unawareness is multifactorial in origin and may be partly reversible.

Awareness↗
PubMed1991

Accuracy of blood glucose estimation by children with IDDM and their parents.

OBJECTIVE: To evaluate the accuracy of blood glucose symptom recognition and subjective blood glucose estimation in insulin-dependent diabetic (IDDM) children and their parents. RESEARCH DESIGN AND METHODS: Blood glucose estimation questionnaires were completed 4 times/day at home during routine activities. A sequential sample of 19 families, who attended a pediatric diabetes clinic, with IDDM children less than 12 yr old and IDDM duration of greater than or equal to 9 mo comprised the study. RESULTS: Error grid analysis showed that both children and parents demonstrated poor accuracy, making clinically significant errors as frequently as clinically accurate estimates. The most common error was the failure to detect extreme blood glucose levels, with a significant tendency to underestimate hyperglycemia. Children often reported hypoglycemia when blood glucose was hyperglycemic. Confidence in the ability to estimate blood glucose was unrelated to measured accuracy. CONCLUSIONS: IDDM children and their parents demonstrated a higher rate of blood glucose estimation errors than IDDM adolescents and adults in previous studies. Even in families who use self-monitoring of blood glucose frequently, self-reported ability to recognize symptoms and estimate blood glucose should be viewed with caution. Families with IDDM children need more education about errors in symptom recognition and blood glucose estimation. They should also be encouraged to use self-monitoring of blood glucose before treating children's reported hypoglycemic symptoms whenever possible.

Adult↗
PubMed1990

Environmental stress and blood glucose change in insulin-dependent diabetes mellitus.

Blood glucose (BG) response to psychological stress in insulin-dependent diabetes mellitus (IDDM) patients has not been firmly established. We report a study designed to address the gaps and methodological difficulties reviewed. Subjects with IDDM were exposed to two sessions (12 weeks apart) of two 20-min standardized stressors (active and passive) and a control condition administered in counterbalanced order. To measure BG response, subjects were connected to a glucose/insulin infusion system providing continuous BG measurement. Mood checklist measures were obtained at prestressor, poststressor, and recovery periods. During the first session of testing, the active stressor was associated with significantly more absolute change in BG response than the passive stressor. Results also indicate that IDDM subjects' BG response to this active stressor was idiosyncratic but significantly reliable over time.

Arousal↗
PubMed1989

Glucose enhancement of performance on memory tests in young and aged humans.

Recent findings indicate that glucose administration enhances memory processes in rodents. This study examined the effects of glucose on memory in humans. After drinking glucose- or saccharin-flavored beverages, college-aged and elderly humans were tested with modified versions of the Wechsler Memory Scale. Beverages and tests were administered in a counter-balanced, crossover design, enabling within subject comparisons. The major findings were: (1) glucose enhanced memory in elderly and, to a lesser extent, in young subjects; and (2) glucose tolerance in individual subjects predicted memory in elderly, but not in young subjects on both glucose and saccharin test days.

Adolescent↗
PubMed1989

Mood changes associated with blood glucose fluctuations in insulin-dependent diabetes mellitus.

Individuals with insulin-dependent diabetes mellitus (IDDM) and their healthcare practitioners believe that extreme blood glucose (BG) fluctuations are characterized by changes in subjective mood states and emotional behavior, as well as physical symptoms. This study examined relationships between BG levels and self-reported mood in a group of 34 IDDM adults. The method followed a within-subject, repeated-measures design employed in previous studies of physical symptoms associated with diabetic glucose. Four times each day, participants completed a mood/symptom checklist just prior to a self-measurement of BG until 40 checklists had been completed. Half the items on the checklist described physical symptoms and half described mood states. In addition, half the mood items described negative states and half described positive states. Within-subject correlations and regressions showed that moods were related to BG for the majority of participants and that, like physical symptoms, mood-BG relationships were highly idiosyncratic. Low BG levels tended to be associated with negative mood states, primarily self-reported "nervousness." Positive mood items were almost always associated with high BG. High BG levels also frequently correlated with negative mood states, although the negative mood items that tended to relate to high glucose (anger, sadness) differed from those that tended to relate to low BG. The implications of these findings for self-treatment and glucose perception in the IDDM individual are discussed.

Adult↗
PubMed1989

Effects and correlates of blood glucose awareness training among patients with IDDM.

Whereas self-monitoring of blood glucose (SMBG) is the recommended source of information on which to make self-care decisions, patients frequently use estimates of their own blood glucose (BG). This study evaluated whether patients with insulin-dependent diabetes mellitus (IDDM) could learn to improve accuracy of BG estimations and whether this would lead to improved metabolic control. Subjects in BG awareness training improved both their BG-estimation accuracy and glycosylated hemoglobin (HbA1) compared with the control group. Initial BG-estimation accuracy was marginally associated with pretreatment HbA1 and months of previous SMBG experience. Posttreatment improvement was associated with pretreatment BG-estimation accuracy and the ability to counterregulate to insulin-induced hypoglycemia.

Blood Glucose↗
PubMed1988

Blood glucose discrimination training in insulin-dependent diabetes mellitus (IDDM) patients.

Self-management of insulin-dependent diabetes mellitus (IDDM) is dependent on a negative feedback loop of blood glucose (BG) fluctuations, which in turn directs treatment decisions to maintain normal BG. Although this feedback is typically accomplished by self-monitoring of blood glucose (SMBG), SMBG has limitations, and patients often rely on what their BG "feels" like. Two studies were performed to evaluate whether patients could learn to more accurately "feel"/discriminate their BG on the basis of internal cues or internal plus external BG cues. In Study I, BG Awareness Training significantly improved pre- to posttreatment BG estimation accuracy, relative to a control group. Study II replicated BG Awareness Training efficacy in improving BG estimation accuracy. Improvement in estimation accuracy was related only to initial accuracy; those who were initially less accurate improved the most. This improvement was represented in a 31% reduction in dangerous BG estimation errors and a 9% increase in accurate estimates. Resulting estimations were, however, still significantly less accurate than SMBG at the end of training.

Adult↗
PubMed1988

Metabolic and cutaneous events associated with hypoglycemia detected by sleep sentry.

Eighteen insulin-dependent diabetic subjects [age (mean +/- SD) 33.2 +/- 10.6 yr] participated in a study designed to determine the metabolic and cutaneous parameters associated with activation of the nocturnal hypoglycemia monitor Sleep Sentry. Plasma glucose, glucagon, epinephrine, norepinephrine, and pancreatic polypeptide concentrations were determined every 10 min during a 2-h constant intravenous insulin infusion (40 mU.kg-1.h-1). In addition, skin temperature and electrical conductance were monitored at the same time intervals, and subjects were asked to rate the degree to which they felt cold and/or sweaty. Ten of the subjects (alarmers) activated the device with a mean plasma glucose nadir of 52.8 +/- 13.8 mg/dl, whereas eight (nonalarmers) failed to do so despite a mean plasma glucose nadir of 50.5 +/- 8.2 mg/dl. There were no significant differences between alarmers and nonalarmers with respect to initial or nadir plasma glucose levels, rate of fall of plasma glucose, or changes in plasma epinephrine, norepinephrine, or pancreatic polypeptide concentrations. In addition, changes in skin temperature and conductance were similar in both groups as were descriptive variables including age, disease duration, gender, and level of glucose control. No subject reported an increase in coldness, whereas 80% of both groups reported an increase in sweatiness. Three subjects studied on more than one occasion over a year failed to exhibit consistent activation of the alarm. This study suggests that it may not be possible to identify patients for whom the Sleep Sentry would be a reliable addition to their self-management regimen and that physicians should exercise caution in recommending its use.

Adult↗