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Biomedical subjects

Daniel Cox

Publications and source records attributed to Daniel Cox.

11 recordsLinked to original sources
PubMed2006

Evaluation of a new measure of blood glucose variability in diabetes.

OBJECTIVE: Recent studies show the importance of controlling blood glucose variability in relationship to both reducing hypoglycemia and attenuating the risk for cardiovascular and behavioral complications due to hyperglycemia. It is therefore important to design variability measures that are equally predictive of low and high blood glucose excursions. RESEARCH DESIGN AND METHODS: We introduce the average daily risk range (ADRR), a variability measure computed from routine self-monitored blood glucose (SMBG) data. The ADRR was constructed using a development dataset for 39 and 31 adults with type 1 and type 2 diabetes, respectively. The formula was then fixed, and the ADRR was compared against other variability measures using an independent validation dataset containing approximately 4 months of SMBG for 254 and 81 adults with type 1 and type 2 diabetes. RESULTS: From the 1st month of validation SMBG data, we computed the ADRR, blood glucose SD and coefficient of variation, daily blood glucose range and interquartile range, mean amplitude of glycemic excursion, M-value, and lability index. Then all measures were tested as predictors of low blood glucose (<2.2 mmol/l; <3.9 mmol/l) and high (>10 mmol/l; >22.2 mmol/l) events in the subsequent 3 months. The ADRR was the best predictor of both hypoglycemia and hyperglycemia, with a 6-fold increase in the likelihood of hypoglycemia and 3.5-fold increase in the likelihood of hyperglycemia across its risk categories. CONCLUSIONS: In a large SMBG database, the ADRR showed strong association with subsequent out-of-control glucose readings. Compared with other variability measures, the ADRR demonstrated a superior balance of sensitivity to predicting both hypoglycemia and hyperglycemia. This prediction was independent from type of diabetes.

Adult↗
PubMed2005

Randomized controlled clinical trial of Blood Glucose Awareness Training (BGAT III) in Switzerland and Germany.

Although both diabetes and the efficacy of medical management are international issues, psycho-educational interventions might be culturally bound. Blood Glucose Awareness Training (BGAT) is a psycho-educational program for patients with type 1 diabetes mellitus. It is focused on improving recognition and management of extreme blood glucose levels, and is the best documented American psycho-educational program for this purpose. A randomized controlled clinical trial of BGAT's long-term benefits in a non-American setting has been lacking. One hundred and eleven adults with type 1 diabetes mellitus from Switzerland and Germany participated. After a 6 months baseline assessment, subjects were randomly assigned to receive either 2 months of BGAT (n = 56) or a physician-guided self-help control intervention (n = 55). BGAT improved recognition of low (p = 0.008), high (p = .03), and overall blood glucose (p = 0.001), and reduced frequency of severe hypoglycemia (p = 0.04), without compromising metabolic control. BGAT reduced both the external locus of control (p < 0.02) and fear of hypoglycemia (p < 0.02). BGAT was efficacious in reducing adverse clinical events and achieving clinically desirable goals in a European, as well as American setting.

Analysis of Variance↗
PubMed2005

Calibration of ADHD assessments across studies: a meta-analysis tool.

When analyzed separately, data from small studies provide only limited information with limited clinical generalizability, due to small sample size, differing assessments, and limited scope. In this methodological paper we outline a theoretical framework for performing meta-analysis of data obtained from disparate studies using disparate tests, based on calibration of the data from such studies and tests into a unified probability scale. We apply this method to combine the data from five studies examining the diagnostic abilities of different assessments of Attention Deficit/Hyperactivity Disorder (ADHD), including behavioral rating scales and EEG assessments. The studies enrolled a total of 111 subjects, 56 ADHD and 55 controls. Each individual study had a small sample focused on a specific age/gender group, for example 8 boys ages 6-10, and generally had insufficient power to detect statistically significant differences. No gender, or age comparisons were possible within any single study. However, when calibrated and combined, the data resulted in a clear separation between ADHD versus non-ADHD groups in males below the age of 16 (p < 0.001), males above the age of 16, (p = 0.015), females below the age of 16, (p = 0.0014), and females above the age of 16, (p = 0.0022). We conclude that if data from various studies using various tests are made comparable, the resulting combined sample size and the increased diversity of the combined sample lead to increased significance of the statistical tests and allow for cross-sectional comparisons, which are not possible within each individual study.

Adolescent↗
PubMed2005

Evaluating the clinical accuracy of two continuous glucose sensors using continuous glucose-error grid analysis.

OBJECTIVE: To compare the clinical accuracy of two different continuous glucose sensors (CGS) during euglycemia and hypoglycemia using continuous glucose-error grid analysis (CG-EGA). RESEARCH DESIGN AND METHODS: FreeStyle Navigator (Abbott Laboratories, Alameda, CA) and MiniMed CGMS (Medtronic, Northridge, CA) CGSs were applied to the abdomens of 16 type 1 diabetic subjects (age 42 +/- 3 years) 12 h before the initiation of the study. Each system was calibrated according to the manufacturer's recommendations. Each subject underwent a hyperinsulinemic-euglycemic clamp (blood glucose goal 110 mg/dl) for 70-210 min followed by a 1-mg.dl(-1).min(-1) controlled reduction in blood glucose toward a nadir of 40 mg/dl. Arterialized blood glucose was determined every 5 min using a Beckman Glucose Analyzer (Fullerton, CA). CGS glucose recordings were matched to the reference blood glucose with 30-s precision, and rates of glucose change were calculated for 5-min intervals. CG-EGA was used to quantify the clinical accuracy of both systems by estimating combined point and rate accuracy of each system in the euglycemic (70-180 mg/dl) and hypoglycemic (<70 mg/dl) ranges. RESULTS: A total of 1,104 data pairs were recorded in the euglycemic range and 250 data pairs in the hypoglycemic range. Overall correlation between CGS and reference glucose was similar for both systems (Navigator, r = 0.84; CGMS, r = 0.79, NS). During euglycemia, both CGS systems had similar clinical accuracy (Navigator zones A + B, 88.8%; CGMS zones A + B, 89.3%, NS). However, during hypoglycemia, the Navigator was significantly more clinically accurate than the CGMS (zones A + B = 82.4 vs. 61.6%, Navigator and CGMS, respectively, P < 0.0005). CONCLUSIONS: CG-EGA is a helpful tool for evaluating and comparing the clinical accuracy of CGS systems in different blood glucose ranges. CG-EGA provides accuracy details beyond other methods of evaluation, including correlational analysis and the original EGA.

Adult↗
PubMed2004

Effect of restraint systems on maxillofacial injury in frontal motor vehicle collisions.

PURPOSE: Motor vehicle collisions (MVCs) are the leading cause of maxillofacial fractures. Additionally, maxillofacial injuries are the most common injury related to air bag deployment. We sought to characterize the occupant restraint system (seat belt and air bag) and collision characteristics associated with MVC-related maxillofacial injuries. MATERIALS AND METHODS: The 1991-2000 National (United States) Automotive Sampling System Crashworthiness Data System (CDS) data files were used. The CDS is a national probability sample of passenger vehicles involved in police-reported tow-away MVCs. Analysis was limited to front seat occupants involved in frontal collisions of delta-V (estimated change in velocity) of greater than 15 km/hr. The risk of facial injury was calculated according to occupants' restraint use (unrestrained, seat belt only, air bag only, and seat belt and air bag combined) and compared using risk ratios (RRs) and associated 95% confidence intervals (CIs). RESULTS: Occupants restrained with a seat belt only (RR, 0.48; 95% CI, 0.40 to 0.57) or a seat belt and an air bag (RR, 0.83; 95% CI, 0.73 to 0.94) had a significantly reduced risk of any facial injury compared with completely unrestrained occupants. There was no association for those restrained with an air bag only (RR, 1.19; 95% CI, 0.82 to 1.73). A similar pattern of results was observed for moderate to severe facial injuries and for facial fractures. CONCLUSION: Seat belt use significantly reduces the risk of facial injury in frontal MVCs. Air bag use was not associated with the risk of facial injury.

Accidents, Traffic↗
PubMed2004

Combined psychophysiological assessment of ADHD: a pilot study of Bayesian probability approach illustrated by appraisal of ADHD in female college students.

Manifestations of ADHD are observed at both psychological and physiological levels and assessed via various psychometric, EEG, and imaging tests. However, no test is 100% accurate in its assessment of ADHD. This study introduces a stochastic assessment combining psychometric tests with previously reported (Consistency Index) and newly developed (Alpha Blockade Index) EEG-based physiological markers of ADHD. The assessment utilizes classical Bayesian inference to refine after each step the probability of ADHD of each individual. In a pilot study involving six college females with ADHD and six matched controls, the assessment achieved correct classification for all ADHD and non-ADHD participants. In comparison, the classification of ADHD versus non-ADHD participants was < 85% for any one of the tests separately. The procedure significantly improved the score separation between ADHD versus non-ADHD groups. The final average probabilities for ADHD were 76% for the ADHD group and 8% for the control group. These probabilities correlated (r = .87) with the Brown ADD scale and (r = .84) with the ADHD-Symptom Inventory used for the screening of the participants. We conclude that, although each separate test was not completely accurate, a combination of several tests classified correctly all ADHD and all non-ADHD participants. The application of the proposed assessment is not limited to the specific tests used in this study--the assessment represents a general paradigm capable of accommodating a variety of ADHD tests into a single diagnostic assessment.

Adult↗
PubMed2004

Increased high-frequency heart rate variability during insulin-induced hypoglycaemia in healthy humans.

Despite causing sympathetic activation, prolonged hypoglycaemia produces little change in HR (heart rate) in healthy young adults. One explanation could be concurrent parasympathetic activation, resulting in unchanged net effects of autonomic influences. In the present study, hypoglycaemic (2.7 mmol/l) and normoglycaemic (4.7 mmol/l) hyperinsulinaemic clamp studies were performed after normoglycaemic baseline clamp periods with 15 healthy volunteers (seven male; mean age, 27 years) on two occasions in a randomized single-blind cross-over design. Non-invasive indices of cardiac autonomic activity and hormones were measured at baseline and 1 h after the beginning of hypoglycaemia or control normoglycaemia. Plasma insulin levels and mean HR were similar during both conditions. During hypoglycaemia, there was a 485% increase in plasma adrenaline (epinephrine). A shortening of the pre-ejection period by 45% suggested strong sympathetic cardiac activation. High-frequency (0.15-0.45 Hz) HRV (HR variability) increased, indicating a concomitant increase in parasympathetic tone. Thus, during hypoglycaemia-induced sympathetic cardiac activation in healthy adults, parasympathetic mechanisms are involved in stabilizing mean HR.

Adult↗
PubMed2003

Cognitive and psychomotor function in hypoglycemia: response error patterns and retest reliability.

Hypoglycemia has been shown to impair cognitive and psychomotor function, but it has been unclear which measures are most reliable and sensitive for detecting these effects. In a single-blind repeated measures design, healthy young adults (N=17, 8 male, mean age 27 years) performed three PC-based cognitive and psychomotor function tests: a paced auditory serial addition task (PASAT), an adaptive five-choice reaction time test (CRTT), and a manual tracking test on two occasions 4 weeks apart. In each session, a hyperinsulinemic clamp method was used during a normoglycemic (plasma glucose: 4.7 mmol/l) baseline testing period, followed in one session by a normoglycemic target testing period, and in the other session by a hypoglycemic (2.7 mmol/l) target testing period. All cognitive and psychomotor function measures showed high test-retest reliability (r ranging from.69 to.95) and sensitivity to hypoglycemia (P<.01). A new finding is that on the PASAT, hypoglycemia appears to differentially increase the rate of omission errors more than it increases false responses. Data on PASAT reaction time (RT) are also presented.

Adult↗
PubMed2002

Abnormal vascular function and hypertension in mice deficient in estrogen receptor beta.

Blood vessels express estrogen receptors, but their role in cardiovascular physiology is not well understood. We show that vascular smooth muscle cells and blood vessels from estrogen receptor beta (ERbeta)-deficient mice exhibit multiple functional abnormalities. In wild-type mouse blood vessels, estrogen attenuates vasoconstriction by an ERbeta-mediated increase in inducible nitric oxide synthase expression. In contrast, estrogen augments vasoconstriction in blood vessels from ERbeta-deficient mice. Vascular smooth muscle cells isolated from ERbeta-deficient mice show multiple abnormalities of ion channel function. Furthermore, ERbeta-deficient mice develop sustained systolic and diastolic hypertension as they age. These data support an essential role for ERbeta in the regulation of vascular function and blood pressure.

Adrenergic alpha-Agonists↗
PubMed2002

The effects of glucose fluctuation on cognitive function and QOL: the functional costs of hypoglycaemia and hyperglycaemia among adults with type 1 or type 2 diabetes.

It is traditionally believed that while acute hypoglycaemia has detectable negative consequences, such as unpleasant symptoms and cognitive-motor disruptions, acute hyperglycaemia is not associated with such consequences. However, recent research with adults affected by either type 1 or 2 diabetes mellitus demonstrates that relatively mild hyperglycaemia is associated with unpleasant symptoms and cognitive disruptions. Both hyperglycaemia and hypoglycaemia can be associated with patient experiences of physical, affective, and cognitive symptoms, as well as cognitive-motor disruptions. These effects can lead to impaired functioning and quality of life. Because these effects are different across patients, their significance can be difficult to appreciate. There is ample evidence that acute hypoglycaemia is a problem for both adults with type 1 and those with type 2 diabetes, and that mild and moderate hypoglycaemia reduce one's mental efficiency relative to euglycaemic performance. There is growing evidence that transient hyperglycaemia has similar negative effects. At relatively mild levels of extreme blood glucose--either hypoglycaemia or hyperglycaemia--cognitive efficiency may decay by a third. The impact of this effect will depend on the task the patient is dealing with at the time. If the person is engaging in a relatively dangerous task, such as driving a vehicle, significant consequences could follow. Both hypoglycaemia and hyperglycaemia have been demonstrated to have not only acute, but also chronic effects in patients with type 1 as well as those with type 2 diabetes. Although hypoglycaemia occurs at a lower rate among patients with type 2 diabetes than among those with type 1, the number of patients with type 2 diabetes is so large that even this low rate results in many persons being affected.

Acute Disease↗