M. Carrington

Autonomic activity during human sleep as a function of time and sleep stage.

While there is a developing understanding of the influence of sleep on cardiovascular autonomic activity in humans, there remain unresolved issues. In particular, the effect of time within the sleep period, independent of sleep stage, has not been investigated. Further, the influence of sleep on central sympathetic nervous system (SNS) activity is uncertain because results using the major method applicable to humans, the low frequency (LF) component of heart rate variability (HRV), have been contradictory, and because the method itself is open to criticism. Sleep and cardiac activity were measured in 14 young healthy subjects on three nights. Data was analysed in 2‐min epochs. All epochs meeting specified criteria were identified, beginning 2 h before, until 7 h after, sleep onset. Epoch values were allocated to 30‐min bins and during sleep were also classified into stage 2, slow wave sleep (SWS) and rapid eye movement (REM) sleep. The measures of cardiac activity were heart rate (HR), blood pressure (BP), high frequency (HF) and LF components of HRV and pre‐ejection period (PEP). During non‐rapid eye movement (NREM) sleep autonomic balance shifted from sympathetic to parasympathetic dominance, although this appeared to be more because of a shift in parasympathetic nervous system (PNS) activity. Autonomic balance during REM was in general similar to wakefulness. For BP and the HF and LF components the change occurred abruptly at sleep onset and was then constant over time within each stage of sleep, indicating that any change in autonomic balance over the sleep period is a consequence of the changing distribution of sleep stages. Two variables, HR and PEP, did show time effects reflecting a circadian influence over HR and perhaps time asleep affecting PEP. While both the LF component and PEP showed changes consistent with reduced sympathetic tone during sleep, their pattern of change over time differed.

Atrial fibrillation: Profile and burden of an evolving epidemic in the 21st century

BACKGROUND Atrial fibrillation (AF) represents an increasing public health challenge with profound social and economic implications. METHODS A comprehensive synthesis and review of the AF literature was performed. Overall, key findings from 182 studies were used to describe the indicative scope and impact of AF from an individual to population perspective. RESULTS There are many pathways to AF including advancing age, cardiovascular disease and increased levels of obesity/metabolic disorders. The reported population prevalence of AF ranges from 2.3%-3.4% and historical trends reflect increased AF incidence. Estimated life-time risk of AF is around 1 in 4. Primary care contacts reflect whole population trends: AF-related case-presentations increase from less than 0.5% in those aged 40 years or less to 6-12% for those aged 85 years or more. Globally, AF-related hospitalisations (primary or secondary diagnosis) showed an upward trend (from ~35 to over 100 admissions/10,000 persons) during 1996 to 2006. The estimated cost of AF is greater than 1% of health care expenditure and rising with hospitalisations the largest contributor. For affected individuals, quality of life indices are poor and AF confers an independent 1.5 to 2.0-fold probability of death in the longer-term. AF is also closely linked to ischaemic stroke (3- to 5-fold risk), chronic heart failure (up to 50% develop AF) and acute coronary syndromes (up to 25% develop AF) with consistently worse outcomes reported with concurrent AF. Future projections predict at least a doubling of AF cases by 2050. SUMMARY AF represents an evolving, global epidemic providing considerable challenges to minimise its impact from an individual to whole society perspective.

The effects of normal aging on sleep spindle and K-complex production

OBJECTIVES Despite a relatively large body of literature describing the characteristics of sleep spindles and K-complexes in young adults, relatively little research has been conducted in older individuals. The general consensus from the few studies that have addressed this issue is that there is a progressive decrease in the number of spindles and K-complexes with age, although there is large intra-individual variation. Whether or not these changes are an inevitable consequence of the aging process can be addressed by studying healthy older adults who provide an example of the effects of age independently from those of disease. METHODS Fourteen young adults (mean age=21.4+/-2.5 years) and 20 older adults (mean age=75.5+/-6.3 years) participated in the study. All subjects were neurologically and medically healthy and were not taking any medications with a known effect on the central nervous system or sleep. For each subject, a number of characteristics were determined including the number, density (SS/min), amplitude and frequency of all spindles as well as the number and density of K-complexes (KC/min). RESULTS Spindle number, density and duration as well as K-complex number and density were all significantly lower in the elderly compared to the young adults. The EEG frequency within the spindles was significantly higher in the elderly, although the absolute difference was less than 0.5 Hz. Multiple regression analysis indicated that spindle duration and K-complex density were able to predict over 90% of the variance in age. CONCLUSIONS The age-related decrease in sleep spindle and K-complex density is consistent with previous reports and may be interpreted as an age-related alteration of thalamocortical regulatory mechanisms.

Incidence and characteristics of newly diagnosed rheumatic heart disease in Urban African adults: insights from the Heart of Soweto Study

AIMS Little is known on the incidence and clinical characteristics of newly diagnosed rheumatic heart disease (RHD) in adulthood from urban African communities in epidemiologic transition. METHODS AND RESULTS Chris Hani Baragwanath Hospital services the black African community of 1.1 million people in Soweto, South Africa. A prospective, clinical registry captured data from all de novo cases of structural and functional valvular heart disease (VHD) presenting to the Cardiology Unit during 2006/07. We describe in detail all cases with newly diagnosed RHD. There were 4005 de novo presentations in 2006/07 and 960 (24%) had a valvular abnormality. Of these, 344 cases (36%) were diagnosed with RHD. Estimated incidence of new cases of RHD for those aged >14 years in the region was 23.5 cases/100 000 per annum. Most were black African females (n = 234-68%) with a similar age profile to males [median 41 (interquartile range 30-55) years vs. 42 (interquartile range 31-55) years]. The predominant valvular lesion (n = 204, 59%) was mitral regurgitation (MR), with 48 (14%) and 43 (13%) cases, respectively, having combination lesions of aortic plus MR and mixed mitral VHD. Impaired systolic function was found in 28/204 cases (14%) of predominant MR and in 23/126 cases (18%) with predominant aortic regurgitation. Elevated right ventricular systolic pressure >35 mmHg (62 cases), atrial fibrillation (34 cases), and anaemia (27 cases) were found in 18, 10, and 8% of 344 RHD cases, respectively. Subsequent valve replacement/repair was performed in 75 patients (22%). A total of 90 cases (26%) were admitted within 30 months of initial diagnosis for suspected bacterial endocarditis. CONCLUSION These data reveal a high incidence of newly diagnosed RHD within an adult urban African community. These data argue strongly for the first episode of RHD to be made a notifiable condition in high burden countries in order to ensure control of the disease through register-based secondary prophylaxis programmes.

A time bomb of cardiovascular risk factors in South Africa: results from the Heart of Soweto Study "Heart Awareness Days"

BACKGROUND There is strong anecdotal evidence that many urban communities in Sub-Saharan Africa are in epidemiologic transition with the subsequent emergence of more affluent causes of heart disease. However, data to describe the risk factor profile of affected communities is limited. METHODS During 9 community screening days undertaken in the predominantly Black African community of Soweto, South Africa (population 1 to 1.5 million) in 2006-2007, we examined the cardiovascular risk factor profile of volunteers. Screening comprised a combination of self-reported history and a clinical assessment that included calculation of body mass index (BMI), blood pressure and random blood glucose and total cholesterol levels. RESULTS In total, we screened a total of 1691 subjects (representing almost 0.2% of the total population). The majority (99%) were Black African, there were more women (65%) than men and the mean age was 46+/-14 years. Overall, 78% of subjects were found to have >or=1 major risk factor for heart disease. By far the most prevalent risk factor overall was obesity (43%) with significantly more obese women than men (23% versus 55%: OR 1.76 95% CI 1.62 to 1.91: p<0.001). A further 33% of subjects had high blood pressures (systolic or diastolic) and 13% an elevated (non-fasting) total blood cholesterol level: no statistically significant differences between the sexes were found. There was a positive correlation between increasing BMI and other risk factors including elevated systolic (r(2)=0.046, p<0.001) and diastolic blood pressure (r(2)=0.032, p<0.001) with overweight subjects three times more likely to have concurrent hypercholesterolemia (OR 3.3, 95% CI 2.1 to 5.3: p<0.01). CONCLUSIONS These unique pilot data strongly suggest a high prevalence of related risk factors for heart disease in this urban black African population in epidemiologic transition. Further research is needed to confirm our findings and to determine their true causes and potential consequences.

Impact of home versus clinic-based management of chronic heart failure: the WHICH? (Which Heart Failure Intervention Is Most Cost-Effective & Consumer Friendly in Reducing Hospital Care) multicenter, randomized trial.

OBJECTIVES The goal of this study was to make a head-to-head comparison of 2 common forms of multidisciplinary chronic heart failure (CHF) management. BACKGROUND Although direct patient contact appears to be best in delivering CHF management overall, the precise form to optimize health outcomes is less clear. METHODS This prospective, multicenter randomized controlled trial with blinded endpoint adjudication comprised 280 hospitalized CHF patients (73% male, age 71 ± 14 years, and 73% with left ventricular ejection fraction ≤45%) randomized to home-based intervention (HBI) or specialized CHF clinic-based intervention (CBI). The primary endpoint was all-cause, unplanned hospitalization or death during 12- to 18-month follow-up. Secondary endpoints included type/duration of hospitalization and healthcare costs. RESULTS The primary endpoint occurred in 102 of 143 (71%) HBI versus 104 of 137 (76%) CBI patients (adjusted hazard ratio [HR]: 0.97 [95% confidence interval (CI): 0.73 to 1.30], p = 0.861): 96 (67.1%) HBI versus 95 (69.3%) CBI patients had an unplanned hospitalization (p = 0.887), and 31 (21.7%) versus 38 (27.7%) died (p = 0.252). The median duration of each unplanned hospitalization was significantly less in the HBI group (4.0 [interquartile range (IQR): 2.0 to 7.0] days vs. 6.0 [IQR: 3.5 to 13] days; p = 0.004). Overall, 75% of all hospitalization was attributable to 64 (22.9%) patients, of whom 43 (67%) were CBI patients (adjusted odds ratio: 2.55 [95% CI: 1.37 to 4.73], p = 0.003). HBI was associated with significantly fewer days of all-cause hospitalization (-35%; p = 0.003) and from cardiovascular causes (-37%; p = 0.025) but not for CHF (-24%; p = 0.218). Consequently, healthcare costs (

Nature's clocks and human mood: the circadian system modulates reward motivation

AU3.93 vs.

Contribution of the human immunodeficiency virus/acquired immunodeficiency syndrome epidemic to de novo presentations of heart disease in the Heart of Soweto Study cohort

AU5.53 million) were significantly less for the HBI group (median:

Effect of intensive structured care on individual blood pressure targets in primary care: multicentre randomised controlled trial

AU34 [IQR: 13 to 81] per day vs.

Mild cognitive impairment in high-risk patients with chronic atrial fibrillation: a forgotten component of clinical management?

AU52 [17 to 140] per day; p = 0.030). CONCLUSIONS HBI was not superior to CBI in reducing all-cause death or hospitalization. However, HBI was associated with significantly lower healthcare costs, attributable to fewer days of hospitalization. (Which Heart failure Intervention is most Cost-effective & consumer friendly in reducing Hospital care [WHICH?]; ACTRN12607000069459).