Standard versus atrial fibrillation-specific management strategy (SAFETY) to reduce recurrent admission and prolong survival: pragmatic, multicentre, randomised controlled trial

BACKGROUND

Patients are increasingly being admitted with chronic atrial fibrillation, and disease-specific management might reduce recurrent admissions and prolong survival. However, evidence is scant to support the application of this therapeutic approach. We aimed to assess SAFETY--a management strategy that is specific to atrial fibrillation.

METHODS

We did a pragmatic, multicentre, randomised controlled trial in patients admitted with chronic, non-valvular atrial fibrillation (but not heart failure). Patients were recruited from three tertiary referral hospitals in Australia. 335 participants were randomly assigned by computer-generated schedule (stratified for rhythm or rate control) to either standard management (n=167) or the SAFETY intervention (n=168). Standard management consisted of routine primary care and hospital outpatient follow-up. The SAFETY intervention comprised a home visit and Holter monitoring 7-14 days after discharge by a cardiac nurse with prolonged follow-up and multidisciplinary support as needed. Clinical reviews were undertaken at 12 and 24 months (minimum follow-up). Coprimary outcomes were death or unplanned readmission (both all-cause), measured as event-free survival and the proportion of actual versus maximum days alive and out of hospital. Analyses were done on an intention-to-treat basis. The trial is registered with the Australian New Zealand Clinical Trials Registry (ANZCTRN 12610000221055).

FINDINGS

During median follow-up of 905 days (IQR 773-1050), 49 people died and 987 unplanned admissions were recorded (totalling 5530 days in hospital). 127 (76%) patients assigned to the SAFETY intervention died or had an unplanned readmission (median event-free survival 183 days [IQR 116-409]) and 137 (82%) people allocated standard management achieved a coprimary outcome (199 days [116-249]; hazard ratio 0·97, 95% CI 0·76-1·23; p=0·851). Patients assigned to the SAFETY intervention had 99·5% maximum event-free days (95% CI 99·3-99·7), equating to a median of 900 (IQR 767-1025) of 937 maximum days alive and out of hospital. By comparison, those allocated to standard management had 99·2% (95% CI 98·8-99·4) maximum event-free days, equating to a median of 860 (IQR 752-1047) of 937 maximum days alive and out of hospital (effect size 0·22, 95% CI 0·21-0·23; p=0·039).

INTERPRETATION

A post-discharge management programme specific to atrial fibrillation was associated with proportionately more days alive and out of hospital (but not prolonged event-free survival) relative to standard management. Disease-specific management is a possible strategy to improve poor health outcomes in patients admitted with chronic atrial fibrillation.

FUNDING

National Health and Medical Research Council of Australia.

Blood pressure, brain structure, and cognition: opposite associations in men and women

BACKGROUND

Research on associations between blood pressure, brain structure, and cognitive function has produced somewhat inconsistent results. In part, this may be due to differences in age ranges studied and because of sex differences in physiology and/or exposure to risk factors, which may lead to different time course or patterns in cardiovascular disease progression. The aim of this study was to investigate the impact of sex on associations between blood pressure, regional cerebral volumes, and cognitive function in older individuals.

METHODS

In this cohort study, brachial blood pressure was measured twice at rest in 266 community-based individuals free of dementia aged 68-73 years who had also undergone a brain scan and a neuropsychological assessment. Associations between mean blood pressure (MAP), regional brain volumes, and cognition were investigated with voxel-wise regression analyses.

RESULTS

Positive associations between MAP and regional volumes were detected in men, whereas negative associations were found in women. Similarly, there were sex differences in the brain-volume cognition relationship, with a positive relationship between regional brain volumes associated with MAP in men and a negative relationship in women.

CONCLUSIONS

In this cohort of older individuals, higher MAP was associated with larger regional volume and better cognition in men, whereas opposite findings were demonstrated in women. These effects may be due to different lifetime risk exposure or because of physiological differences between men and women. Future studies investigating the relationship between blood pressure and brain structure or cognitive function should evaluate the potential for differential sex effects.

Temporal divergence of percent body fat and body mass index in pre-teenage children: the LOOK longitudinal study

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The index of body mass related to stature, (body mass index, BMI, kgm(-2) ), is widely used as a proxy for percent body fat (%BF) in cross-sectional and longitudinal investigations. BMI does not distinguish between lean and fat mass and in children, the cross-sectional relationship between %BF and BMI changes with age and sex.

WHAT THIS STUDY ADDS

While BMI increases linearly with age from age 8 to 12 years in both boys and girls, %BF plateaus off between 10 and 12 years. Repeated measures in children show a systematic decrease in %BF for any given BMI from age 8 to 10 to 12 years. Because changes in BMI misrepresent changes in %BF, its use as a proxy of %BF should be avoided in longitudinal studies in this age group.

BACKGROUND

Body mass index (BMI, kgm(-2) ) is commonly used as an indicator of pediatric adiposity, but with its inability to distinguish changes in lean and fat mass, its use in longitudinal studies of children requires careful consideration.

OBJECTIVE

To investigate the suitability of BMI as a surrogate of percent body fat (%BF) in pediatric longitudinal investigations.

METHODS

In this longitudinal study, healthy Australian children (256 girls and 278 boys) were measured at ages 8.0 (standard deviation 0.3), 10.0 and 12.0 years for height, weight and percent body fat (%BF) by dual-energy X-ray absorptiometry.

RESULTS

The patterns of change in the means of %BF and BMI were different (P < 0.001). While mean BMI increased linearly from 8 to 12 years of age, %BF did not change between 10 and 12 years. Relationships between %BF and BMI in boys and girls were curvilinear and varied with age (P < 0.001) and gender (P < 0.001); any given BMI corresponding with a lower %BF as a child became older.

CONCLUSION

Considering the divergence of temporal patterns of %BF and BMI between 10 and 12 years of age, employment of BMI as a proxy for %BF in absolute or age and sex standardized forms in pediatric longitudinal investigations is problematical.

A systematic approach to chronic heart failure care: a consensus statement

The National Heart Foundation of Australia assembled an expert panel to provide guidance on policy and system changes to improve the quality of care for people with chronic heart failure (CHF). The recommendations have the potential to reduce emergency presentations, hospitalisations and premature death among patients with CHF. Best-practice management of CHF involves evidence-based, multidisciplinary, patient-centred care, which leads to better health outcomes. A CHF care model is required to achieve this. Although CHF management programs exist, ensuring access for everyone remains a challenge. This is particularly so for Aboriginal and Torres Strait Islander peoples, those from non-metropolitan areas and lower socioeconomic backgrounds, and culturally and linguistically diverse populations. Lack of data and inadequate identification of people with CHF prevents efficient patient monitoring, limiting information to improve or optimise care. This leads to ineffectiveness in measuring outcomes and evaluating the CHF care provided. Expanding current cardiac registries to include patients with CHF and developing mechanisms to promote data linkage across care transitions are essential. As the prevalence of CHF rises, the demand for multidisciplinary workforce support will increase. Workforce planning should provide access to services outside of large cities, one of the main challenges it is currently facing. To enhance community-based management of CHF, general practitioners should be empowered to lead care. Incentive arrangements should favour provision of care for Aboriginal and Torres Strait Islander peoples, those from lower socioeconomic backgrounds and rural areas, and culturally and linguistically diverse populations. Ongoing research is vital to improving systems of care for people with CHF. Future research activity needs to ensure the translation of valuable knowledge and high-quality evidence into practice.

Physical education can improve insulin resistance: the LOOK randomized cluster trial

PURPOSE

As impaired glucose metabolism may arise progressively during childhood, we sought to determine whether the introduction of specialist-taught school physical education (PE) based on sound educational principles could improve insulin resistance (IR) in elementary school children.

METHODS

In this 4-yr cluster-randomized intervention study, participants were 367 boys and 341 girls (mean age = 8.1 yr, SD = 0.35) initially in grade 2 in 29 elementary schools situated in suburbs of similar socioeconomic status. In 13 schools, 100 min·wk-1 of PE, usually conducted by general classroom teachers, was replaced with two classes per week taught by visiting specialist PE teachers; the remaining schools formed the control group. Teacher and pupil behavior were recorded, and measurements in grades 2, 4, and 6 included fasting blood glucose and insulin to calculate the homeostatic model of IR, percent body fat, physical activity, fitness, and pubertal development.

RESULTS

On average, the intervention PE classes included more fitness work than the control PE classes (7 vs 1 min, P < 0.001) and more moderate physical activity (17 vs 10 min, P < 0.001). With no differences at baseline, by grade 6, the intervention had lowered IR by 14% (95% confidence interval = 1%-31%) in the boys and by 9% (95% confidence interval = 5%-26%) in the girls, and the percentage of children with IR greater than 3, a cutoff point for metabolic risk, was lower in the intervention than the control group (combined, 22% vs 31%, P = 0.03; boys, 12% vs 21%, P = 0.06; girls, 32% vs 40%, P = 0.05).

CONCLUSIONS

Specialist-taught primary school PE improved IR in community-based children, thereby offering a primordial preventative strategy that could be coordinated widely although a school-based approach.

Central hemodynamics could explain the inverse association between height and cardiovascular mortality

BACKGROUND

Mechanisms underlying the inverse relationship between height and cardiovascular mortality are unknown but could relate to central hemodynamics. We sought to determine the relation of height to central and peripheral hemodynamics, as well as clinical characteristics.

METHODS

The study population was comprised of 1,152 randomly selected community-dwelling adults (aged 67.7 ± 12.3 years; 48% men). Brachial blood pressure (BP) was recorded by sphygmomanometry; central BP and aortic pulse wave velocity were estimated by applanation tonometry. Stepwise multiple regression analysis was used to determine associations between height and central and peripheral hemodynamics.

RESULTS

Height was not significantly associated with aortic pulse wave velocity in men or women. The relationship with height and brachial systolic BP was borderline in women (β = -0.115; P = 0.051) but not significant in men (β = -0.096; P = 0.09). Conversely, central systolic BP, estimated by transfer function (β = -0.139 for men [βM]; β = -0.172 for women [βW]) or radial second systolic peak (β M = -0.239; β W = -0.281), augmentation index at 75 bpm (β M = -0.189; β W = -0.224), and aortic pulse wave timing (β M = 0.224; β W = 0.262) were independently associated with height in both sexes (P < 0.003 for all). Both men and women of greater than median height were less likely to have coronary artery disease (P < 0.05), to have systemic hypertension (P < 0.01), or to be taking vasoactive medication (P < 0.001) compared with participants of less than median height.

CONCLUSIONS

Even after correcting for conventional cardiovascular risk factors, taller individuals have more favorable central hemodynamics and reduced evidence of coronary artery disease compared with shorter individuals. These findings may help explain the decreased cardiovascular risk associated with being taller and also have important clinical consequences regarding therapy.

Deterioration in renal function is associated with increased arterial stiffness

BACKGROUND

Higher levels of baseline pulse wave velocity (PWV) have been associated with longitudinal decline in renal function in patients with kidney disease. We examined longitudinal decline in renal function in relation to levels of PWV. We hypothesized that longitudinal decline in renal function in a community-based, nonclinic sample would be associated with higher levels of PWV.

METHODS

We conducted a 4-5 year longitudinal study with 482 community-living individuals free from acute stroke, dementia, and end-stage renal disease (mean age = 60.9 years; 59% women; 93.2% white; 10% with diabetes mellitus; mean estimated glomerular filtration rate (eGFR) = 79.2 ml/min/1.73 m2). Multiple linear regression analyses were used to examine the association between changes in renal function (eGFR and serum creatinine) from baseline to follow-up and PWV levels at follow-up, the outcome measure. Regression coefficients were adjusted for age, sex, education, race/ethnicity, weight, activity level, mean arterial pressure, treatment of hypertension, and cardiovascular risk factors.

RESULTS

With adjustment for covariables, decline in renal function was associated with higher levels of PWV over a mean follow-up of 4.68 years.

CONCLUSIONS

Decline in renal functioning from baseline levels measured 4-5 years before measurement of PWV is related to higher levels of PWV in a community sample.

Effect of weight reduction and cardiometabolic risk factor management on symptom burden and severity in patients with atrial fibrillation: a randomized clinical trial

IMPORTANCE

Obesity is a risk factor for atrial fibrillation. Whether weight reduction and cardiometabolic risk factor management can reduce the burden of atrial fibrillation is not known.

OBJECTIVE

To determine the effect of weight reduction and management of cardiometabolic risk factors on atrial fibrillation burden and cardiac structure.

DESIGN, SETTING, AND PATIENTS

Single-center, partially blinded, randomized controlled study conducted between June 2010 and December 2011 in Adelaide, Australia, among overweight and obese ambulatory patients (N = 150) with symptomatic atrial fibrillation. Patients underwent a median of 15 months of follow-up.

INTERVENTIONS

Patients were randomized to weight management (intervention) or general lifestyle advice (control). Both groups underwent intensive management of cardiometabolic risk factors.

MAIN OUTCOMES AND MEASURES

The primary outcomes were Atrial Fibrillation Severity Scale scores: symptom burden and symptom severity. Scores were measured every 3 months from baseline to 15 months. Secondary outcomes performed at baseline and 12 months were total atrial fibrillation episodes and cumulative duration measured by 7-day Holter, echocardiographic left atrial area, and interventricular septal thickness.

RESULTS

Of 248 patients screened, 150 were randomized (75 per group) and underwent follow-up. The intervention group showed a significantly greater reduction, compared with the control group, in weight (14.3 and 3.6 kg, respectively; P < .001) and in atrial fibrillation symptom burden scores (11.8 and 2.6 points, P < .001), symptom severity scores (8.4 and 1.7 points, P < .001), number of episodes (2.5 and no change, P = .01), and cumulative duration (692-minute decline and 419-minute increase, P = .002). Additionally, there was a reduction in interventricular septal thickness in the intervention and control groups (1.1 and 0.6 mm, P = .02) and left atrial area (3.5 and 1.9 cm2, P = .02).

CONCLUSIONS AND RELEVANCE

In this study, weight reduction with intensive risk factor management resulted in a reduction in atrial fibrillation symptom burden and severity and in beneficial cardiac remodeling. These findings support therapy directed at weight and risk factors in the management of atrial fibrillation.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12610000497000.

Physical education and blood lipid concentrations in children: the LOOK randomized cluster trial

Background and Objectives

Elevated blood lipids during childhood are predictive of dyslipidemia in adults. Although obese and inactive children have elevated values, any potentially protective role of elementary school physical education is unknown. Our objective was to determine the effect of a modern elementary school physical education (PE) program on the blood lipid concentrations in community-based children.

Methods

In this cluster-randomized controlled trial, 708 healthy children (8.1±0.3 years, 367 boys) in 29 schools were allocated to either a 4-year intervention program of specialist-taught PE (13 schools) or to a control group of the currently practiced PE conducted by generalist classroom teachers. Fasting blood lipids were measured at ages 8, 10, and 12 years and intervention and control class activities were recorded.

Results

Intervention classes included more fitness work and more moderate and vigorous physical activity than control classes (both p<0.001). With no group differences at baseline, the percentage of 12 year-old boys and girls with elevated low density lipoprotein cholesterol (LDL-C, >3.36mmol.L⁻¹,130 mg/dL) was lower in the intervention than control group (14% vs. 23%, p = 0.02). There was also an intervention effect on mean LDL-C across all boys (reduction of 9.6% for intervention v 2.8% control, p = 0.02), but not girls (p = 0.2). The intervention effect on total cholesterol mirrored LDL-C, but there were no detectable 4-year intervention effects on high-density lipoprotein cholesterol or triglycerides.

Conclusions

The PE program delivered by specialist teachers over four years in elementary school reduced the incidence of elevated LDL-C in boys and girls, and provides a means by which early preventative practices can be offered to all children.

Trial Registration

Australia New Zealand Clinical Trial Registry ANZRN12612000027819 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=347799.

Aortic stiffness in lone atrial fibrillation: a novel risk factor for arrhythmia recurrence

Background

Recent community-based research has linked aortic stiffness to the development of atrial fibrillation. We posit that aortic stiffness contributes to adverse atrial remodeling leading to the persistence of atrial fibrillation following catheter ablation in lone atrial fibrillation patients, despite the absence of apparent structural heart disease. Here, we aim to evaluate aortic stiffness in lone atrial fibrillation patients and determine its association with arrhythmia recurrence following radio-frequency catheter ablation.

Methods

We studied 68 consecutive lone atrial fibrillation patients who underwent catheter ablation procedure for atrial fibrillation and 50 healthy age- and sex-matched community controls. We performed radial artery applanation tonometry to obtain central measures of aortic stiffness: pulse pressure, augmentation pressure and augmentation index. Following ablation, arrhythmia recurrence was monitored at months 3, 6, 9, 12 and 6 monthly thereafter.

Results

Compared to healthy controls, lone atrial fibrillation patients had significantly elevated peripheral pulse pressure, central pulse pressure, augmentation pressure and larger left atrial dimensions (all P<0.05). During a mean follow-up of 2.9±1.4 years, 38 of the 68 lone atrial fibrillation patients had atrial fibrillation recurrence after initial catheter ablation procedure. Neither blood pressure nor aortic stiffness indices differed between patients with and without atrial fibrillation recurrence. However, patients with highest levels (≥75^th percentile) of peripheral pulse pressure, central pulse pressure and augmentation pressure had higher atrial fibrillation recurrence rates (all P<0.05). Only central aortic stiffness indices were associated with lower survival free from atrial fibrillation using Kaplan-Meier analysis.

Conclusion

Aortic stiffness is an important risk factor in patients with lone atrial fibrillation and contributes to higher atrial fibrillation recurrence following catheter ablation procedure.

Effect of population selection on 99th percentile values for a high sensitivity cardiac troponin I and T assays

OBJECTIVE

Using objective laboratory and clinical criteria to more accurately determine the 99th percentile values for cardiac troponin I and T.

DESIGN AND METHODS

We measured cardiac troponin T and cardiac troponin I with high-sensitivity assays in a large cohort of apparently healthy community subjects and calculated 99th percentiles for different sexes and ages. Subjects with possible subclinical disease were eliminated based on objective laboratory criteria, eGFR and NT-proBNP, and clinical criteria, history and examination and echocardiogram.

RESULTS

For men and women of all ages, separately, more than 50% of subjects were excluded using these criteria, with a lesser proportion of younger subjects being excluded. In men aged <75 years, the 99th percentile for cTnI decreased by more than 50% from 22.9 ng/L to 10.3 ng/L. In other age groups and for cTnT the decrease was smaller (%) but still considerable.

CONCLUSIONS

For establishing cardiac troponin 99th percentiles, simply using self-reporting of health is insufficient. Objective laboratory measures and clinical and echocardiographic assessments are essential to define a healthy population, especially in older persons.

Waiting a few extra minutes before measuring blood pressure has potentially important clinical and research ramifications

Office blood pressure (BP) is recommended to be measured after 5 min of seated rest, but it may decrease for 10 min of seated rest. This study aimed to determine the change (and its clinical relevance) in brachial and central BP from 5 to 10 min of seated rest. Office brachial and central BP (measured after 5 and 10 min), left ventricular (LV) mass index, 7-day home and ambulatory BP were measured in 250 participants with treated hypertension. Office brachial and central BP were significantly lower at 10-min compared with 5-min BP (P<0.001). Seven-day home systolic BP (SBP) was significantly lower than office SBP measured at 5 min (P<0.001), but was similar to office SBP at 10 min (P=0.511). From 5 to 10 min, the percentage of participants with controlled BP increased and the percentage of participants with high central pulse pressure (PP) decreased (P<0.001). Moreover, brachial and central PP were significantly correlated with LV mass index measured at 10 min (r=0.171, P=0.006 and r=0.139, P=0.027, respectively), but not at 5 min (r=0.115, P=0.068 and r=0.084, P=0.185, respectively). BP recorded after 10 min is more representative of true BP control. These findings have relevance to appropriate diagnosis of hypertension and design of clinical trials.

Myocardial perfusion and the J curve association between diastolic blood pressure and mortality

BACKGROUND

The J-curve relationship between brachial diastolic blood pressure (DBP) and mortality is believed to be mediated through reduced myocardial perfusion. This study aimed to determine the relationship between DBP and subendocardial perfusion in patients with and without coronary artery disease (CAD) and to examine central hemodynamic variables that may explain the risk associated with low DBP (aortic stiffness, central pulse pressure, and augmentation index).

METHODS

Brachial DBP and radial tonometry were measured in 134 patients with CAD (aged 76±7years; 69% male), 134 individuals without a prior cardiovascular event (control subjects) (aged 77±2years; 69% male) and 47 patients (aged 63±10years) during dobutamine stress echocardiography. Central hemodynamics and subendocardial viability ratio (SEVR), a marker of subendocardial perfusion, were recorded by tonometry.

RESULTS

There was no difference in DBP or SEVR between control subjects and CAD patients (P > 0.05), nor was there a difference in SEVR across quartiles of DBP in CAD patients (P = 0.07) or control subjects (P = 0.14). After adjustment for age and height, associations between DBP and SEVR in control subjects (r = 0.185; P = 0.03) and CAD patients (r = 0.204; P = 0.02) were attenuated (P = 0.07 and P = 0.11, respectively). There were no significant relationships between DBP and central hemodynamics (P > 0.05 for all). At peak dobutamine stress, SEVR was significantly reduced in patients with inducible ischemia vs. those with nonischemic response (84±17 vs. 101±22%; P = 0.01). However, DBP was not significantly different (65±14 vs. 67±15mm Hg; P = 0.32).

CONCLUSIONS

Brachial DBP is a poor marker of subendocardial perfusion. The J-curve relationship between DBP and mortality is unlikely attributable to reduced myocardial perfusion or adverse central hemodynamics.

Erectile dysfunction severity as a risk marker for cardiovascular disease hospitalisation and all-cause mortality: a prospective cohort study

BACKGROUND

Erectile dysfunction is an emerging risk marker for future cardiovascular disease (CVD) events; however, evidence on dose response and specific CVD outcomes is limited. This study investigates the relationship between severity of erectile dysfunction and specific CVD outcomes.

METHODS AND FINDINGS

We conducted a prospective population-based Australian study (the 45 and Up Study) linking questionnaire data from 2006-2009 with hospitalisation and death data to 30 June and 31 Dec 2010 respectively for 95,038 men aged ≥45 y. Cox proportional hazards models were used to examine the relationship of reported severity of erectile dysfunction to all-cause mortality and first CVD-related hospitalisation since baseline in men with and without previous CVD, adjusting for age, smoking, alcohol consumption, marital status, income, education, physical activity, body mass index, diabetes, and hypertension and/or hypercholesterolaemia treatment. There were 7,855 incident admissions for CVD and 2,304 deaths during follow-up (mean time from recruitment, 2.2 y for CVD admission and 2.8 y for mortality). Risks of CVD and death increased steadily with severity of erectile dysfunction. Among men without previous CVD, those with severe versus no erectile dysfunction had significantly increased risks of ischaemic heart disease (adjusted relative risk [RR] = 1.60, 95% CI 1.31-1.95), heart failure (8.00, 2.64-24.2), peripheral vascular disease (1.92, 1.12-3.29), "other" CVD (1.26, 1.05-1.51), all CVD combined (1.35, 1.19-1.53), and all-cause mortality (1.93, 1.52-2.44). For men with previous CVD, corresponding RRs (95% CI) were 1.70 (1.46-1.98), 4.40 (2.64-7.33), 2.46 (1.63-3.70), 1.40 (1.21-1.63), 1.64 (1.48-1.81), and 2.37 (1.87-3.01), respectively. Among men without previous CVD, RRs of more specific CVDs increased significantly with severe versus no erectile dysfunction, including acute myocardial infarction (1.66, 1.22-2.26), atrioventricular and left bundle branch block (6.62, 1.86-23.56), and (peripheral) atherosclerosis (2.47, 1.18-5.15), with no significant difference in risk for conditions such as primary hypertension (0.61, 0.16-2.35) and intracerebral haemorrhage (0.78, 0.20-2.97).

CONCLUSIONS

These findings give support for CVD risk assessment in men with erectile dysfunction who have not already undergone assessment. The utility of erectile dysfunction as a clinical risk prediction tool requires specific testing.

The distribution of cardiac troponin I in a population of healthy children: lessons for adults

OBJECTIVES

To describe the distribution of hs-cTnI in a large cohort of healthy children.

DESIGN AND METHODS

As part of the LOOK study, blood was collected from a large cohort of healthy children on 3 separate occasions when the children were aged 8, 10 and 12years. Samples were stored at -80°C after collection and assayed after 1 freeze-thaw cycle using a pre-commercial release hs-cTnI assay from Abbott Diagnostics.

RESULTS

More than 98% of the 12year-old children had cTnI above the LoD of 1.0ng/L. For the 212 boys the central 95% of results was distributed in a Gaussian fashion. For the 237 girls, the initial analysis was non-Gaussian, but after the elimination of 2 results, the pattern for girls was also Gaussian.

CONCLUSIONS

In healthy children, cTnI is present in a Gaussian distribution. Even minor illnesses can cause some troponin release, distorting this Gaussian distribution.

Longitudinal Studies of Cardiac Troponin I in a Large Cohort of Healthy Children

BACKGROUND

There is little information available on cardiac troponin concentrations in healthy young children.

METHODS

Using a precommercial high-sensitivity assay from Abbott Diagnostics, we measured cardiac troponin I (cTnI) in longitudinal blood samples collected at ages 8, 10, and 12 years from a cohort of healthy, community-dwelling children. The 99th percentile values were calculated and estimates of the long-term biological variation were made.

RESULTS

cTnI concentrations were above the limit of detection in 87%, 90%, and 98% of the children at ages 8, 10, and 12 years. The 99th percentiles were lower compared to a healthy adult population in both male and female children at all ages studied. At the 3 periods of study assessment, different children had cTnI concentrations above the 99th percentile. The calculated 99th percentile varied markedly depending upon whether the lowest or highest cTnI measurement for an individual child was included in the calculation. Biological variation varied markedly between 0% and 136%, the index of individuality was low at 0.36, and the reference change value was an increase of 147% or a decrease of 59%.

CONCLUSIONS

In this longitudinal study of cTnI concentrations in healthy children as determined by a high-sensitivity assay, different children had concentrations of cTnI above the 99th percentile at the 3 episodes of assessment. These results suggest that in children the 99th percentile may not be a reliable index of silent cardiac disease, but rather may be indicating low-grade intercurrent illness.

Determinants of childhood adiposity: evidence from the Australian LOOK study

BACKGROUND

To contribute to the current debate as to the relative influences of dietary intake and physical activity on the development of adiposity in community-based children.

METHODS

Participants were 734 boys and girls measured at age 8, 10 and 12 years for percent body fat (dual emission x-ray absorptiometry), physical activity (pedometers, accelerometers); and dietary intake (1 and 2-day records), with assessments of pubertal development and socioeconomic status.

RESULTS

Cross-sectional relationships revealed that boys and girls with higher percent body fat were less physically active, both in terms of steps per day and moderate and vigorous physical activity (both sexes p<0.001 for both measures). However, fatter children did not consume more energy, fat, carbohydrate or sugar; boys with higher percent body fat actually consumed less carbohydrate (p = 0.01) and energy (p = 0.05). Longitudinal analysis (combined data from both sexes) was weaker, but supported the cross-sectional findings, showing that children who reduced their PA over the four years increased their percent body fat (p = 0.04). Relationships in the 8 year-olds and also in the leanest quartile of all children, where adiposity-related underreporting was unlikely, were consistent with those of the whole group, indicating that underreporting did not influence our findings.

CONCLUSIONS

These data provide support for the premise that physical activity is the main source of variation in the percent body fat of healthy community-based Australian children. General community strategies involving dietary intake and physical activity to combat childhood obesity may benefit by making physical activity the foremost focus of attention.

Effects of changes in adiposity and physical activity on preadolescent insulin resistance: the Australian LOOK longitudinal study

Background

In a previous longitudinal analysis of our cohort as 8 to 10 year-olds, insulin resistance (IR) increased with age, but was not modified by changes in percent body fat (%BF), and was only responsive to changes in physical activity (PA) in boys. We aimed to determine whether these responses persisted as the children approached adolescence.

Methods

In this prospective cohort study, 256 boys and 278 girls were assessed at ages 8, 10 and 12 years for fasting blood glucose and insulin, %BF (dual energy X-ray absorptiometry); PA (7-day pedometers), fitness (multistage run); and pubertal development (Tanner stage).

Results

From age 8 to 12 years, the median homeostatic model of IR (HOMA-IR) doubled in boys and increased 250% in girls. By age 12, 23% of boys and 31% of girls had elevated IR, as indicated by HOMA-IR greater than 3. Longitudinal relationships, with important adjustments for covariates body weight, PA, %BF, Tanner score and socioeconomic status showed that, on average, for every 1 unit reduction of %BF, HOMA-IR was lowered by 2.2% (95% CI 0.04–4) in girls and 1.6% (95% CI 0–3.2) in boys. Furthermore, in boys but not girls, HOMA-IR was decreased by 3.5% (95%CI 0.5–6.5) if PA was increased by 2100 steps/day.

Conclusion

Evidence that a quarter of our apparently healthy 12 year-old Australians possessed elevated IR suggests that community-based education and prevention strategies may be warranted. Responsiveness of IR to changes in %BF in both sexes during late preadolescence and to changes in PA in the boys provides a specific basis for targeting elevated IR. That body weight was a strong covariate of IR, independent of %BF, points to the importance of adjusting for weight in correctly assessing these relationships in growing children.