Cardiovascular endurance and heart rate variability in adolescents with type 1 or type 2 diabetes

Hyperglycemia: A determinant of cardiac autonomic dysfunction in youth with obesity across the spectrum of glycemic regulation

OBJECTIVES

To characterize the determinants of heart rate variability (HRV) in youth with obesity across the glycemia spectrum.

METHODS

A total of 94 adolescents, 15 ± 2.1 years (21 with normal weight, 23 with overweight-normal glucose tolerance, 26 with prediabetes and 24 with type 2 diabetes [T2D]) underwent an assessment of body composition (dual-energy x-ray absorptiometry), 2-h oral glucose tolerance test with the calculation of indices of glycemia and insulin sensitivity (IS), inflammatory markers (high-sensitivity C-reactive protein [hs-CRP] and tumour necrosis factor-α [TNF-α]), and HRV by peripheral arterial tonometry.

RESULTS

The HRV frequency-domain index (low-frequency to high-frequency ratio [LF/HF]), an estimate of the ratio between sympathetic and parasympathetic activity, increased across the glycemic spectrum, and was highest in T2D compared with the other three groups (p = 0.004). LF/HF correlated with %body fat (r = 0.22, p = 0.04); fasting (r = 0.39, p < 0.001), 2-h (r = 0.31, p = 0.004), and area under the curve glucose (r = 0.32, p = 0.003); hs-CRP (r = 0.33, p = 0.002) and TNF-α (r = 0.38, p = 0.006). In a linear regression model, fasting glucose (β = 0.39, p = 0.003) and hs-CRP (β = 0.21, p = 0.09) contributed to the variance in Ln LF/HF independent of IS, %body fat, age, sex, race-ethnicity and Tanner stage (R2  = 0.23, p = 0.013).

CONCLUSIONS

Youth with impaired glucose regulation have evidence of cardiac autonomic dysfunction with decreased HRV, and sympathetic overdrive (increased LF/HF). This dysfunction is mainly related to glycemia and systemic inflammation.

A High intensity Interval training (running and swimming) and resistance training intervention on heart rate variability and the selected biochemical factors in boys with type 1 diabetes

OBJECTIVE

The purpose of this research is to investigate the effect of High Intensity Interval Training and Resistance training (HIITR) on heart rate variability (HRV), blood glucose, and plasma biomarkers levels in adolescents with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

24 boys with T1D (FBS: 274.66 ± 52.99, age: 15.2 ± 1.78 years, and BMI = 19.61 ± 1.11) and 12 healthy boys (FBS: 92.75 ± 5.22, age: 15.08 ± 1.67 years, and BMI = 20.26 ± 2.66) were divided into three groups: Diabetes Training (DT, n = 12), Diabetes Control (DC, n = 12), and Healthy Control (HC, n = 12). HRV (24 h) was computed in time and frequency domains, anthropometric, biochemical parameters at rest, and aerobic capacity (VO2peak) obtained during a graded exercise testing (GXT). All variables were evaluated at the baseline and following 12 weeks of exercise training, done 3 days weekly. The statistical method used for data analysis was analysis of covariance (ANCOVA) test.

RESULTS

HRV, Hemoglobin A1c (HbA1c) and Fasting blood sugar (FBS), VO2peak, norepinephrine (NEP), and HDL-C indicated significant differences between both T1D groups compared to HC at baseline (p < 0.001). BMI, LDL-C, TC, and TG parameters were similar in all groups. HRV parameters, VO2peak and HDL-C, and NEP were significantly improved by exercise training, and HbA1c and FBS levels were significantly reduced (p < 0.001). There is a negative and significant correlation between LF/HF Ratio Difference (post-test minus pre-test) and VO2Peak Difference variables (post-test minus pre-test) (p < 0.001).

CONCLUSIONS

The present study suggests the importance of early screening for CVD risk factors in adolescent males with T1D. Also, it was revealed HIITR training compared to other training patterns, and cardiovascular health improves via enhancement of autonomic modulation, VO2peak, plasma lipids, and catecholamine levels.

Association of HbA1c with VO2max in Individuals with Type 1 Diabetes: A Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to evaluate the association between glycemic control (HbA1c) and functional capacity (VO2max) in individuals with type 1 diabetes (T1DM). A systematic literature search was conducted in EMBASE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Knowledge for publications from January 1950 until July 2020. Randomized and observational controlled trials with a minimum number of three participants were included if cardio-pulmonary exercise tests to determine VO2max and HbA1c measurement has been performed. Pooled mean values were estimated for VO2max and HbA1c and weighted Pearson correlation and meta-regression were performed to assess the association between these parameters. We included 187 studies with a total of 3278 individuals with T1DM. The pooled mean HbA1c value was 8.1% (95%CI; 7.9−8.3%), and relative VO2max was 38.5 mL/min/kg (37.3−39.6). The pooled mean VO2max was significantly lower (36.9 vs. 40.7, p = 0.001) in studies reporting a mean HbA1c > 7.5% compared to studies with a mean HbA1c ≤ 7.5%. Weighted Pearson correlation coefficient was r = −0.19 (p < 0.001) between VO2max and HbA1c. Meta-regression adjusted for age and sex showed a significant decrease of −0.94 mL/min/kg in VO2max per HbA1c increase of 1% (p = 0.024). In conclusion, we were able to determine a statistically significant correlation between HbA1c and VO2max in individuals with T1DM. However, as the correlation was only weak, the association of HbA1c and VO2max might not be of clinical relevance in individuals with T1DM.

Cardiac Autonomic Modulation in Response to Three Types of Exercise in Patients with Type 2 Diabetic Neuropathy

Purpose

Physical exercise is necessary in the handling DM, but it is not distinct which kind of physical exercise can improve cardiac autonomic modulation in T2DM. The purpose of this study was to compare the effects of three different modalities of exercise (aerobic, resistant, and combined) on cardiac autonomic modulation as measured by HRV in patients with type 2 diabetic neuropathy.

Methods

The participants were 45 men (age: 55.24 ± 8.11 years, weight: 89.5 ± 13.4 kg, height: 171.85 ± 6.98 cm, duration of diabetes: 12.51 ± 6.46 years) with type 2 diabetic neuropathy who were clinically free from signs and symptoms of cardiovascular disease. Participants were randomly assigned to one of four groups: aerobic-training (n = 11), dynamic resistant-training (n = 11), Combined-training (n = 11), or a non-exercise control group (n = 12). The exercise groups performed aerobic and resistant exercise for 25-45 min per day, 3-5 times per week for 12 weeks. Anthropometrics, biochemical markers (FBS, HbA1c, Lipid Profile, and Insulin), and heart rate variability in the exercise laboratory and under ambulatory conditions by 3-channel ECG digital Holter recorder were examined.

Results

All time and frequency-domain HRV parameters (except LF power) were significantly improved in the exercise groups, compared with the control group (p < 0.05). SDNN, rMSSD, and HF power were boosted, LF power was not different, and the LF/HF ratio decreased after versus before exercise training, independent of exercise modality. HbA1c in aerobic and resistant-training groups, and insulin and LDL in the resistant-training group were decreased after exercise training (p < 0.05).

Conclusions

Exercise training, independent of modality, in patients with type 2 diabetic neuropathy who were clinically free of the cardiovascular disease cause to significant progress in cardiovascular autonomic function assessed by HRV via enhancing cardio-vagal and reducing cardio-sympathetic tone.

Effect of exercise training on heart rate variability in type 2 diabetes mellitus patients: A systematic review and meta-analysis

Background

Cardiac autonomic neuropathy is a common complication of type 2 diabetes mellitus (T2DM), that can be measured through heart rate variability (HRV)–known to be decreased in T2DM. Physical exercise can improve HRV in healthy population, however results are under debate in T2DM. We conducted a systemic review and meta-analysis to assess the effects of physical exercise on HRV in T2DM patients.

Method

PubMed, Cochrane, Embase, and ScienceDirect databases were searched for all studies reporting HRV parameters in T2DM patients before and after exercise training, until September 20th 2020, without limitation to specific years. We conducted random-effects meta-analysis stratified by type of exercise for each of the HRV parameters: RR–intervals (or Normal to Normal intervals–NN), standard deviation of RR intervals (SDNN), percentage of adjacent NN intervals varying by more than 50 milliseconds (pNN50), root mean square of successive RR-intervals differences (RMSSD), total power, Low Frequency (LF), High Frequency (HF) and LF/HF ratio. Sensitivity analyses were computed on studies with the highest quality.

Results

We included 21 studies (9 were randomized) for a total of 523 T2DM patients: 472 had an exercise training and 151 were controls (no exercise). Intervention was endurance (14 studies), resistance (2 studies), endurance combined with resistance (4 studies), and high intensity interval training (HIIT) (4 studies). After exercise training, all HRV parameters improved i.e. an increase in SDNN (effect size = 0.59, 95%CI 0.26 to 0.93), RMSSD (0.62, 0.28 to 0.95), pNN50 (0.62, 0.23 to 1.00), HF (0.58, -0.16 to 0.99), and a decrease in LF (-0.37, -0.69 to -0.05) and LF/HF (-0.52, -0.79 to -0.24). There were no changes in controls. Stratification by type of exercise showed an improvement in most HRV parameters (SDNN, RMSSD, pNN50, LF, HF, LF/HF) after endurance training, whereas mostly LF/HF was improved after both resistance training and HIIT. Supervised training improved most HRV parameters. Duration and frequency of training did not influence the benefits on HRV.

Conclusion

Exercise training improved HRV parameters in T2DM patients which may reflect an improvement in the activity of the autonomic nervous system. The level of proof is the highest for endurance training. Supervised training seemed beneficial.

Heart Rate Variability and Cardiac Autonomic Dysfunction: Prevalence, Risk Factors, and Relationship to Arterial Stiffness in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) Study

OBJECTIVE

To determine whether prior type 2 diabetes (T2D) treatment or glycemic control over time are independently associated with heart rate variability (HRV) and whether the presence of cardiac autonomic dysfunction is associated with arterial stiffness in young adults with youth-onset T2D enrolled in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) study.

RESEARCH DESIGN AND METHODS

Heartbeats over 10 min were measured to derive the normal R-Rs (NN intervals). Outcomes included the standard deviation of the NN intervals (SDNN), the root mean square differences of successive NN intervals (RMSSD), percent of NN beats that differ by more than 50 ms (PNN50), and the low-frequency (LF) power domain, high-frequency (HF) power domain, and their ratio (LF:HF). Autonomic dysfunction was defined as ≥3 of 5 abnormal HRV indices compared with obese controls from a separate study.

RESULTS

A total of 397 TODAY participants were evaluated 7 years after randomization. TODAY participants had reduced HRV (SDNN 58.1 ± 29.6 ms vs. controls 67.1 ± 25.4 ms; P < 0.0001) with parasympathetic loss (RMSSD 53.2 ± 36.7 ms vs. controls 67.9 ± 35.2 ms; P < 0.0001) with sympathetic overdrive (LF:HF ratio 1.4 ± 1.7 vs. controls 1.0 ± 1.1; P < 0.0001). Cardiac autonomic dysfunction was present in 8% of TODAY participants, and these participants had greater pulse wave velocity compared with those without dysfunction (P = 0.0001). HRV did not differ by randomized treatment, but higher hemoglobin A1c (HbA_1c) over time was independently associated with lower SDNN and RMSSD and higher LF:HF ratio after adjustment for age, race-ethnicity, sex, and BMI.

CONCLUSIONS

Young adults with youth-onset T2D show evidence of cardiac autonomic dysfunction with both parasympathetic and sympathetic impairments that are associated with higher HbA_1c.

Association of evening smartphone use with cardiac autonomic nervous activity after awakening in adolescents living in high school dormitories

PURPOSE

Smartphones are prevalently used among adolescents; however, nighttime exposure to blue-enriched light, through electric devices, is known to induce delays of the circadian rhythm phases and poor morning somatic conditions. We therefore investigated whether evening smartphone use may affect sleep-wake cycle and cardiac autonomic nervous system (ANS) activity after awaking in dormitory students.

METHODS

The participants were high school students, living under dormitory rules regarding the curfew, study, meals, lights-out, and wake-up times. The students were forbidden from the use of both television and personal computer in their private rooms, and only the use of a smartphone was permitted. According to prior assessment of smartphone use, we chose age-, sex-, exercise time-matched long (n = 22, >120 min) and short (n = 14, ≤60 min) groups and compared sleep-wake cycle and physiological parameters, such as cardiac ANS activity, blood pressure, and intra-aural temperature. All measurements were performed during 6:30 to 7:00 a.m. in the dormitories.

RESULTS

Compared with the short group, the long group showed a significantly lower cardiac ANS activity (2727 ± 308 vs. 4455 ± 667 ms², p = 0.030) with a tendency toward a high heart rate, in addition to later bedtimes during weekdays and more delayed wake-up times over the weekend. Blood pressure and intra-aural temperature did not differ between the groups.

CONCLUSIONS

In this population, evening smartphone use may be associated with altered sleep-wake cycle and a diminished cardiac ANS activity after awakening could be affecting daytime activities.

Comparative study of cardiac autonomic status by heart rate variability between under-treatment normotensive and hypertensive known type 2 diabetics

Background

Co-existence of hypertension is known in three quarter of Indian type 2 diabetics, this duo having adverse additive effect on cardiovascular health including dysautonomia. Latter can be measured by simple 5 min heart rate variability (HRV) using simple electrocardiogram, which if reduced indicates cardiac risk.

Objective

We compared HRV parameters between hypertensive and normotensive type 2 diabetics, looking for significant difference if any.

Materials and methods

98 hypertensive and 40 normotensive type 2 diabetics treated as outpatients were evaluated for disease control and risk stratification. Five min resting HRV was measured by Variowin HR, software based instrument, using standard protocols to record time domain, frequency domain and Poincare plot parameters. They were compared between groups for difference.

Results

Mean age was 56 and 51 years, duration 6 years and 4 years respectively in hypertensive (HT) and normotensive (NT) group of type 2 diabetics, which did not significantly differ in distribution of risk factors. There was poor glycaemic control (one third) in both groups and good pressure control in HT group. Both groups revealed all reduced HRV parameters with significant difference in-between only for LF/HF ratio (1.29 in HT vs 2.61 in NT group).

Conclusion

Our findings of HRV suggest that in type 2 diabetics with poor glycaemic and good pressure control, hypertension as a co-existing factor does not make significant difference in cardiac dysautonomia emphasizing residual risk despite antihypertensive treatment and need for early HRV screening, strict glycaemic control and other interventions.

Cardiovascular Autonomic Neuropathy and Early Atherosclerosis in Adolescent Type 1 Diabetic Patient

AIM:

To evaluate cardiovascular autonomic neuropathy (CAN) in type 1 Diabetics and to detect its relation to coronary artery calcification.

PATIENTS AND METHODS:

It is a cross sectional study included 62 diabetics and 30 controls. Clinical, laboratory assessment and 24 Hr holter were done for all patients and controls and coronary artery calcium (CAC) scoring by multisclice CT was done for all patients only. T-test, Mann Whitney U test, and stepwise multiple regression were used for statistical analyses.

RESULTS:

CAC score was positive in 8.1 % of patients. Heart rate variability (HRV) was significantly lower in diabetics. All parameters of HRV were insignificantly lower in diabetics with positive CAC score. Patients with microalbuminuria had a significantly lower HRV. HRV had a significant correlation with age of patients, duration of disease, HbA1, and Qtc in diabetics.

CONCLUSION:

Percentage of arrhythmia and early atherosclerosis is high in adolescent type 1 diabetic patients. CAN is associated with early atherosclerosis. Cardiac autonomic neuropathy is associated with older age, longer duration, and poor glycemic control and microalbuminuria.

Cardiac Affection in Type 1 Diabetic Patients in Relation to Omentin

AIM:

To evaluate cardiac affection in type 1 diabetes in relation to Omentin.

PATIENTS AND METHODS:

Sixty two diabetics and 30 volunteer of the same age and sex were included as a control group. Blood sample was taken for assessment of omentin and oxidized low density lipoprotein (OxLDL), glycosylated hemoglobin (HbA1) and lipid profile. Urine sample was taken for assessment of albumin/creatinine ratio. 24 hour holter was also done. T-test, simple correlation followed by stepwise multiple regression analysis was used for analysis of data.

RESULTS:

Parameters of 24 hour holter were significantly lower in diabetics. Omentin was significantly lower, while OxLDL were significantly higher than controls. RMSSD, ST deviation and OxLDL were the parameters related to omentin by stepwise multiple regression analysis in diabetics.

CONCLUSION:

Diabetic patients had a cardiac autonomic neuropathy. A significant reduction of omentin and elevation OxLDL imply that they influence glucose metabolism in type 1 diabetes. Omentin had a significant relation to 24 hr holter which may reflect its role in cardiac affection. Omentin and OxLDL had a role in renal affection.

Poor glycemic control impacts linear and non-linear dynamics of heart rate in DM type 2

INTRODUCTION: It is well known that type 2 diabetes mellitus (T2DM) produces cardiovascular autonomic neuropathy (CAN), which may affect the cardiac autonomic modulation. However, it is unclear whether the lack of glycemic control in T2DM without CAN could impact negatively on cardiac autonomic modulation. Objective: To evaluate the relationship between glycemic control and cardiac autonomic modulation in individuals with T2DM without CAN. Descriptive, prospective and cross sectional study.METHODS: Forty-nine patients with T2DM (51±7 years) were divided into two groups according to glycosylated hemoglobin (HbA1c): G1≤7% and G2>7.0%. Resting heart rate (HR) and RR interval (RRi) were obtained and calculated by linear (Mean iRR; Mean HR; rMSSD; STD RR; LF; HF; LF/HF, TINN and RR Tri,) and non-linear (SD1; SD2; DFα1; DFα2, Shannon entropy; ApEn; SampEn and CD) methods of heart rate variability (HRV). Insulin, HOMA-IR, fasting glucose and HbA1c were obtained by blood tests.RESULTS: G2 (HbA1c≤7%) showed lower values for the mean of iRR; STD RR; RR Tri, TINN, SD2, CD and higher mean HR when compared with G1 (HbA1c > 7%). Additionally, HbA1c correlated negatively with mean RRi (r=0.28, p=0.044); STD RR (r=0.33, p=0.017); RR Tri (r=-0.35, p=0.013), SD2 (r=-0.39, p=0.004) and positively with mean HR (r=0.28, p=0.045). Finally, fasting glucose correlated negatively with STD RR (r=-0.36, p=0.010); RR Tri (r=-0.36, p=0.010); TINN (r=-0.33, p=0.019) and SD2 (r=-0.42, p=0.002).CONCLUSION: We concluded that poor glycemic control is related to cardiac autonomic modulation indices in individuals with T2DM even if they do not present cardiovascular autonomic neuropathy.

Toxic stress, inflammation and symptomatology of chronic complications in diabetes

Diabetes affects at least 382 million people worldwide and the incidence is expected to reach 592 million by 2035. The incidence of diabetes in youth is skyrocketing as evidenced by a 21% increase in type 1 diabetes and a 30.5% increase in type 2 diabetes in the United States between 2001 and 2009. The effects of toxic stress, the culmination of biological and environmental interactions, on the development of diabetes complications is gaining attention. Stress impacts the hypothalamus-pituitary-adrenal axis and contributes to inflammation, a key biological contributor to the pathogenesis of diabetes and its associated complications. This review provides an overview of common diabetic complications such as neuropathy, cognitive decline, depression, nephropathy and cardiovascular disease. The review also provides a discussion of the role of inflammation and stress in the development and progression of chronic complications of diabetes, associated symptomatology and importance of early identification of symptoms of depression, fatigue, exercise intolerance and pain.

Cardiovascular complications of type 2 diabetes in youth

The prevalence of type 2 diabetes mellitus (T2DM) in youth has increased dramatically over the past decades. The literature also suggests that the progression from an impaired glucose tolerance state to established T2DM is more rapid in youth, compared to adults. The presence of significant cardiovascular complications in youth with T2DM, including cardiac, macrovascular, and microvascular remodeling, is another major issue in this younger cohort and poses a significant threat to the healthcare system. However, this issue is only now emerging as a major public health concern, with few data to support optimal treatment targets and strategies to reduce cardiovascular disease (CVD) risk in youth with T2DM. Accordingly, the purpose of this minireview is to better understand the cardiovascular complications in youth with T2DM. We briefly describe the pathophysiology from youth studies, including oxidative stress, inflammation, renin-angiotensin aldosterone system, and epigenetics, which link T2DM and CVD. We also describe the literature concerning the early signs of CVD in youth and potential treatment options to reduce cardiovascular risk.

Gender differences in personality and heart-rate variability

Both personality traits and autonomic functioning show as gender differences, but their relationship is not well understood. Medically unexplained symptoms are related to personality features and can be assessed by autonomic measurement. The patterns are hypothesised to identify gender differences. We recruited 30 male and 30 female healthy volunteers. All participants completed the Tridimensional Personality Questionnaire (TPQ) and heart-rate variability (HRV) measurement. Correlation analysis was performed to identify the relationships between TPQ scores and HRV parameters. For the subjects as a whole, the subdimension harm avoidance 4 (HA4, fatigability and asthenia) was found to be negatively correlated with low-frequency (LF) power, high-frequency (HF) power and total power (TP) of HRV. Novelty seeking 1 (NS1, exploratory excitability) was found to be positively correlated with LF power and TP. Multiple linear regression analysis revealed that the interactions exploratory excitability x gender and fatigability x gender are predictors of LF and HF power, respectively. Our result supports the hypothesis that personality features such as exploratory excitability and fatigability are associated with autonomic functioning and that gender is a moderator in these relationships.

Personalized exercise for adolescents with diabetes or obesity

OBJECTIVE

This study examined adherence to a personalized, community-based exercise intervention by sedentary adolescents with type 1 or type 2 diabetes or those with obesity.

RESEARCH DESIGN AND METHODS

We conducted a pretest-posttest investigation to explore the application of an individualized exercise prescription based upon current fitness level for 39 adolescents (20 with type 1 diabetes, 9 with type 2 diabetes, and 10 obese) over 16 weeks in community settings. Subjects were recruited from a university-based pediatric endocrinology clinic in the southwestern United States. Adherence to the exercise prescription was monitored using accelerometers over the entire intervention period.

RESULTS

Moderate-to-vigorous physical activity (MVPA) levels significantly increased over sedentary baseline values (p < .001), but the average of 42.5 ± 22.1 min/day of MVPA determined at the end of the study was still less than the recommended 60 min/day. Perceptions of health were significantly increased for the total group following the intervention (p = .008). For those with type 1 diabetes, there was a significant association between MVPA duration and percentage change in HbA1c (r = -.526, p = .02).

CONCLUSIONS

Recruitment and retention of adolescent participation in daily exercise is challenging. Personalized approaches that include adolescent choices with family support and ongoing motivation can improve individual exercise adherence and a sense of personal health.

Correlation of cardiorespiratory fitness with risk factors for cardiovascular disease in children with type 1 diabetes mellitus

The objective of this study was to correlate CRF with cardiovascular risk factors in T1DM children.

METHODS

Fifty children and adolescents aged between 9 and 17 years with no diabetes complications and a mean diabetes duration of 4.6 years were selected. Antropometric, sexual maturation and blood pressure data were evaluated. CRF level was assessed with a 20-m shuttle run test. Laboratory tests were performed to verify fasting lipids and glycated hemoglobin. Statistical analyses were made with Pearson partial correlation, t test, and one-way ANOVA, with p≤0.05.

RESULTS

After adjustment for body adiposity and sexual maturity, inverse correlations among CRF and TC, TG, TC/HDL-C, TG/HDL-C, non-HDL-C, and SBP were statistically significant. Variables differing by sex included weight Z score, BMI Z score, skinfold thickness, percentage of body fat, and DBP. Boys had higher CRF compared to girls. CRF and TC differed significantly by sexual maturation status.

CONCLUSION

An inverse and significant relationship between CRF and most lipid profile's components and SBP in poor controlled T1DM children and adolescents was found, independently of body adiposity.

Prediabetes and blood pressure effects on heart rate variability, QT-interval duration, and left ventricular hypertrophy in overweight-obese adolescents

This ancillary, descriptive correlational study examined the effect of glucose regulation, blood pressure (BP), and their combined effects on cardiac autonomic function in 128 overweight-obese 11-18-year-olds. Measures included body mass index, resting BP, fasting glucose, glucose tolerance, and cardiac autonomic function (heart rate variability, QT, and Cornell voltage). After adjusting for age and gender, multivariate analysis of covariance revealed no differences in cardiac autonomic measures based on glucose regulation (p = .319), BP (p = .286), or the interaction between glucose regulation and BP (p = .132). The additive effect of prediabetes and elevated BP did not impact cardiac autonomic function in overweight-obese youth.

Heart rate variability in childhood obstructive sleep apnea

The identification of patients with obstructive sleep apnea (OSA) is important because of morbidities associated with OSA. A previous adult study demonstrated the use of heart rate variability (HRV) as a tool to identify patients with moderate to severe OSA. Either a reduction in time parameters or an increase in LF/HF ratio was seen at overnight or 24-hr studies suggestive of increased sympathetic modulation. To study the feasibility of daytime HRV as a screening tool, a short-term recording of HRV is studied. Since it was shown in adult study that increased normalized LF, decreased normalized HF and increased LF/HF ratio could be detectable during supine rest at daytime awake period, the authors hypothesize that the differences are also detectable in children. Children who underwent sleep polysomnography for suspected OSA were recruited. Subjects were classified OSA if apnea-hypopnea index (AHI) > 1.5/hr and non-OSA if AHI ≤ 1.5/hr. Continuous 1-hr electrocardiographic monitoring was recorded in awake children during the day. Parameters from time domain and frequency domain were analyzed. Seventy-four male and 17 female snoring subjects were included in this study. Fifty-one (56%) and 40 (44%) of them were classified as "non-OSA" and "OSA," respectively. pNN50, a parameter for parasympathetic modulation, was significantly reduced in the OSA group when compared with the non-OSA group. Using multiple regression, all time domain variables were shown to be decreased in OSA group. Our results suggest that 1-hr study of HRV may be a feasible tool in identifying children with OSA.

Cardiovascular fitness and quality of life in adolescents with type 1 or type 2 diabetes

PURPOSE

This descriptive study of adolescents with type 1 or type 2 diabetes examined the relationships between cardiovascular fitness and physical activity (PA) with generic or health-related quality of life (QoL), glycemic control, and lipids.

DESIGN AND METHODS

Graded ergometry testing for fitness, fasting assays for lipids, glycosylated hemoglobin (A1C), and self-reported PA and QoL instruments were completed with 151 adolescents.

RESULTS

Adolescents with type 2 diabetes had lower fitness. Fitness was associated with improved lipids, A1C, health perception, and athletic competence in adolescents with type 1 diabetes.

PRACTICE IMPLICATIONS

Interventions to encourage active lifestyles are imperative for adolescents with diabetes.

Physical activity and electronic media use in the SEARCH for diabetes in youth case-control study

OBJECTIVE

The aim of this study was to characterize the physical activity (PA) and electronic media (EM) use habits of a population-based, ascertained sample of youths with diabetes mellitus (DM).

METHODS

For this investigation, the Search for Diabetes in Youth Case-Control study (age: 10-20 y; 55% female) recruited 384 youths with provider-diagnosed type 1 DM, 90 youths with type 2 DM, and 173 healthy control subjects between 2003 and 2006, in 2 US centers. PA and EM use were assessed with a 3-day recall of activities, in 30-minute time blocks. Adherence to current recommendations was determined as a report of > or = 2 blocks of moderate/vigorous PA per day and <4 blocks of EM use per day. Differences in PA and EM use for DM/control groups were assessed with adjustment for age, study site, and race/ethnicity.

RESULTS

Male subjects with type 2 DM reported lower levels of vigorous PA than did control subjects (1.1 vs 2.3 blocks; P < .05). Compliance with the moderate/vigorous PA recommendation among youths with type 2 DM was lower (68.3%), compared with youths with type 1 DM (81.7%; odds ratio: 0.51 [95% confidence interval: 0.26-1.00]; P = .047) and control subjects (80.4%; odds ratio: 0.48 [95% confidence interval: 0.23-1.02]; P = .05). Rates of compliance with EM use recommendations ranged from 29.5% to 49.1%.

CONCLUSION

In this study, large proportions of youths with DM, especially type 2 DM, failed to meet PA and EM use recommendations.

A personalized approach to exercise promotion in adolescents with type 1 diabetes

PURPOSE

This exploratory study tested the feasibility of conducting a novel, personalized exercise intervention based upon the current fitness levels of adolescents with type 1 diabetes (T1DM). The relationships of perceptions of benefits and barriers to exercise, exercise self-efficacy and family support to exercise adherence and changes in cardiovascular (CV) fitness, quality of life (QOL), and glycemic control were studied.

METHODS

Adolescents who were sedentary received a graded exercise test to determine their current fitness level (VO(2peak)). A 16-wk personalized exercise program was developed for each adolescent based upon individual fitness level and exercise preferences. Pretest and posttest measures of exercise self-efficacy, benefits and barriers to exercise, family support, and diabetes QOL were completed. A1c levels were obtained using the DCA2000. Adherence to exercise was measured using the Actigraph Accelerometer.

RESULTS

Twelve adolescents completed the study. Accelerometry data revealed adherence to 60 min of moderate-to-vigorous physical activity (MVPA) per day for a mean of 45.5 (SD = 23.9)% of the days the accelerometer was worn. Adolescents' perceptions of family support for exercise improved following the intervention (p = 0.03). Adolescents who had more daily bouts of exercise lasting 60 min increased their CV fitness (r = 0.59, p = 0.04). A1c remained unchanged.

CONCLUSIONS

Encouraging 60 min of accumulated exercise bouts/d can improve fitness levels in adolescents with T1DM, minimizing future CV risks. Although physical activity increased in adolescents, family based strategies are required to promote current physical activity recommendations.

Cardiovascular Risks in Adolescents With Diabetes From Vulnerable Populations

Limited data exist on the predisposition for an early trajectory of cardiovascular (CV) disease in adolescents with diabetes. We explored the effects of types of diabetes and sociodemographic factors (i.e., race, gender, income level, family structure) on the following CV risks: glucose control (A1c), blood pressure (BP), and lipid profile. Adolescents with type 1 DM (T1DM) or type 2 DM (T2DM) participated: 109 with T1DM and 42 with T2DM. The general linear model was used to examine the influence of type of DM, sociodemographic factors, and the interaction of type of DM and the sociodemographic factors on CV risks. Systolic and diastolic BP were increased in youth with T2DM versus T1DM. Non-Hispanic Blacks had a higher A1c and resting diastolic BP than non-Hispanic Whites. Lower income was also associated with higher resting diastolic BP. Males with T1DM had higher A1c, whereas females with T2DM had higher A1c. With low income, individuals with T1DM had higher A1c values than those with T2DM; those with high income and T2DM had higher A1c than those with T1DM. Adolescents with T1DM from single, divorced, or separated families had higher average A1c values. In comparison, those with T2DM from married families had higher A1c values. Triglycerides were increased for those with T2DM, with the greatest amount for Hispanics as compared with non-Hispanic Blacks. In summary, minority status, lower income, and family structure may have a greater impact on vulnerability for poor outcomes in adolescents with DM, regardless of the type of the disease.

Microalbuminuria and heart rate variability in adolescents with diabetes

INTRODUCTION

Limited clinical and research data are available on early renal and cardiovascular complications in youth with diabetes. The possible associations of elevated microalbuminuria to creatinine (MC) ratios with heart rate variability (HRV) were explored in adolescents with type 1 (T1DM) or type 2 (T2DM) diabetes.

METHODS

A descriptive study was conducted with 41 adolescents with diabetes (n = 31 T1DM vs. n = 10 T2DM). Twenty-four hour Holter recordings for determining HRV, urine spot checks for MC ratio, and the most recent measures of glycosylated hemoglobin (A1c) were obtained.

RESULTS

HRV was significantly lower in the T2DM group, while body mass index percentile, triglycerides, and diastolic blood pressure were significantly higher. For the T1DM group, clinical case examples provided evidence of elevated MC ratios (>30 mirog/mg) occurring in two female subjects who also had decreased HRV measures.

DISCUSSION

Although HRV was not significantly associated with MC ratios for the sample, individual clinical findings can be a warning sign for some adolescents with diabetes. Current recommendations for screening of early renal complications and associated treatment are provided.

Insulin resistance in adolescents with type 2 diabetes is associated with impaired exercise capacity

CONTEXT

The incidence of pediatric type 2 diabetes (T2D) is rising, with unclear effects on the cardiovascular system. Cardiopulmonary fitness, a marker of morbidity and mortality, is abnormal in adults with T2D, yet the mechanisms are incompletely understood.

OBJECTIVE

We hypothesized that cardiopulmonary fitness would be reduced in youth with T2D in association with insulin resistance (IR) and cardiovascular dysfunction.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a cross-sectional study at an academic hospital that included 14 adolescents (age range, 12-19 yr) with T2D, 13 equally obese adolescents and 12 lean adolescents similar in age, pubertal stage, and activity level.

MAIN OUTCOME MEASURES

Cardiopulmonary fitness was measured by peak oxygen consumption (VO(2)peak) and oxygen uptake kinetics (VO(2)kinetics), IR by hyperinsulinemic clamp, cardiac function by echocardiography, vascular function by venous occlusion plethysmography, body composition by dual-energy x-ray absorptiometry, intramyocellular lipid by magnetic resonance spectroscopy, and inflammation by serum markers.

RESULTS

Adolescents with T2D had significantly decreased VO(2)peak and insulin sensitivity, and increased soleus intramyocellular lipid, C-reactive protein, and IL-6 compared to obese or lean adolescents. Adolescents with T2D also had significantly prolonged VO(2)kinetics, decreased work rate, vascular reactivity, and adiponectin, and increased left ventricular mass and fatty acids compared to lean adolescents. In multivariate linear regression analysis, IR primarily, and fasting free fatty acids and forearm blood flow secondarily, were significant independent predictors of VO(2)peak.

CONCLUSIONS

Given the strong relationship between decreased cardiopulmonary fitness and increased mortality, these findings in children are especially concerning and represent early signs of impaired cardiac function.

Physical fitness, dietary intake, and metabolic control in adolescents with type 1 diabetes

PURPOSE

We examined whether physical fitness and dietary intake predicted better glycemic control and lipid profile in adolescents with type 1 diabetes mellitus (T1DM).

METHODS

The sample consisted of 109 adolescents with T1DM [age, 15.3 +/- 1.9 yr; diabetes duration, 6.2 +/- 3.7 yr; body mass index (BMI), 23.3 +/- 4.0 kg/m(2); and hemoglobin A1c (HbA1c), 8.7 +/- 1.6%]. Stepwise regression analyses were performed with the following independent variables: age, sex, duration of diabetes, BMI, Tanner stage, physical fitness, and average carbohydrate and total and saturated fat intake, and the following dependent variables: total cholesterol, low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), triglycerides, and HbA1c. Physical fitness was measured by peak oxygen consumption (VO(2(peak))) during progressive cycle ergometry, and 3-day food intake was analyzed using Nutritionist Pro software.

RESULTS

Sex and VO(2(peak)) explained 19% of the variance for HbA1c. Age, VO(2(peak)), and saturated fat intake predicted 23% of the variance for total cholesterol, although only diabetes duration and saturated fat intake predicted LDL-c (11%). Duration of diabetes explained 5% of the variance in triglyceride levels, and there were no significant independent predictors for HDL-c.

CONCLUSIONS

Greater fitness levels predicted both better glycemic control and total cholesterol in adolescents with T1DM, whereas lower saturated fat affected total cholesterol but not glycemic control. These findings support the importance of physical fitness and diets of lower saturated fat for overall metabolic health in adolescents with T1DM.

Cardiorespiratory fitness and physical activity in youth with type 2 diabetes

OBJECTIVE

The increased incidence of type 2 diabetes (T2D) among youth is hypothesized to be due, in part, to low levels of fitness and activity. Therefore, the purpose of this investigation was to examine whether cardiorespiratory fitness and physical activity are reduced in youth with T2D compared with overweight controls.

PARTICIPANTS

Thirteen adolescent boys with previously diagnosed T2D (mean duration 2.4 +/- 1.8 yr) were matched for age and body mass index to 13 overweight, non-diabetic controls.

METHODS

Cardiorespiratory fitness was assessed during a progressive exercise test to volitional fatigue and physical activity was estimated from a 7-d physical activity recall.

RESULTS

Youth with T2D reported performing approximately 60% less moderate to vigorous physical activity compared with their non-diabetic counterparts (0.6 +/- 0.2 vs. 1.4 +/- 0.3 h/d, p = 0.04). Furthermore, diabetic youth exhibited significantly lower cardiorespiratory fitness levels compared with controls (28.7 +/- 1.6 vs. 34.6 +/- 2.2 mL/kg/min, p < 0.05).

CONCLUSIONS

These findings support the hypothesis that cardiorespiratory fitness and physical activity are reduced in youth with T2D. Whether reduced fitness and activity contributed to the pathophysiology of the disorder cannot be determined from the cross-sectional analysis. Longitudinal studies are warranted to examine whether improvements in fitness and increased physical activity can prevent the development of T2D in high-risk youth.

Impaired stroke volume and aerobic capacity in female adolescents with type 1 and type 2 diabetes mellitus

AIM/HYPOTHESIS

This study was designed to determine whether type 2 diabetic adolescents have reduced aerobic capacity and to investigate the role of cardiac output and arteriovenous oxygen difference (a-vO(2)) in their exercise response.

METHODS

Female adolescents (age 12-18 years) with type 2 diabetes mellitus (n = 8) and type 1 diabetes mellitus (n = 12) and obese (n = 10) and non-obese (n = 10) non-diabetic controls were recruited for this study. Baseline data included maximal aerobic capacity (cycle ergometer) and body composition. Cardiac output and a-vO(2) were determined at rest and during submaximal exercise.

RESULTS

Diabetic groups had lower aerobic capacity than non-diabetic groups (p < 0.05). Adolescents with type 2 diabetes had lower aerobic capacity than the type 1 diabetic group. Maximal heart rate was lower in the type 2 diabetic group (p < 0.05). Exercise stroke volume was 30-40% lower at 100 and 120 beats per min in the diabetic than in the non-diabetic groups (p < 0.05). The a-vO(2) value was not different in any condition.

CONCLUSIONS AND INTERPRETATION

Type 2 diabetic adolescents have reduced aerobic capacity and reduced heart rate response to maximal exercise. Furthermore, type 2 and type 1 diabetic adolescent girls have a blunted exercise stroke volume response compared with non-diabetic controls. Central rather than peripheral mechanisms contribute to the reduced aerobic capacity in diabetic adolescents. Although of short duration, type 2 diabetes in adolescence is already affecting cardiovascular function in adolescents.