Increased carotid intima-media thickness in remote and urban Indigenous Australians: impact of diabetes and components of the metabolic syndrome

Complex contaminant mixtures and their associations with intima-media thickness

Background

The burden of cardiovascular disease (CVD) morbidity and mortality is higher among Indigenous persons, who also experience greater health disparities when compared to non-Indigenous Canadians, particularly in remote regions of Canada. Assessment of carotid intima-media thickness (cIMT), a noninvasive screening tool and can be used as biomarker to assess increased CVD risk. Few studies have examined environmental contaminant body burden and its association with cIMT.

Methods

Data from the Environment-and-Health Study in the Eeyou Istchee territory of northern Québec, Canada was used to assess complex body burden mixtures of POPs, metals and metalloids among (n = 535) Indigenous people between 15 and 87 years of age with cIMT. First, Principal Component Analysis (PCA) was used to reduce the complexity of the contaminant data. Second, based on the underlying PCA profiles from the biological data, we examined each of the prominent principal component (PC) axes on cIMT using multivariable linear regression models. Lastly, based on these PC axes, cIMT was also regressed on summed (Σ) organic compound concentrations, polychlorinated biphenyl, perfluorinated compounds, respectively, ∑10 OCs, ∑13 PCBs, ∑3PFCs, and nickel.

Results

Most organochlorines and PFCs loaded primarily on PC-1 (53% variation). Nickel, selenium, and cadmium were found to load on PC-5. Carotid-IMT was significantly associated with PC-1 β = 0.004 (95 % CI 0.001, 0.007), and PC-5 β = 0.013 (95 % CI 0.002, 0.023). However, the association appears to be greater for PC-5, accounting for 3% of the variation, and mostly represented by nickel. Results show that that both nickel, and ∑3PFCs were similarly associated with cIMT β = 0.001 (95 % CI 0.0003, 0.003), and β = 0.001 (95 % CI 0.0004, 0.002), respectively. But ∑10OCs was significantly associated with a slightly greater β = 0.004 (95 % CI 0.001, 0.007) cIMT change, though with less precision. Lastly, ∑13PCBs also increased β = 0.002 (95 % CI 0.0004, 0.003) cIMT after fully adjusting for covariates.

Conclusion

Our results suggest that environmental contaminants are associated with cIMT. This is important for the Cree from the Eeyou Istchee territory who may experience higher body burdens of contaminants than non-Indigenous Canadians.

An Overview of Indigenous Australian Disadvantage in Terms of Ischaemic Heart Disease

BACKGROUND

Indigenous Australians experience poorer health outcomes than non-Indigenous Australians and a significant life expectancy gap exists. Ischaemic heart disease (IHD) represents the leading specific cause of death in Indigenous Australians and is a significant, if not the most significant, contributor to the mortality gap. With this narrative review we aim to describe the burden of IHD within the Indigenous Australian community and explore the factors driving this disparity.

METHODS

A broad search of the literature was undertaken utilising an electronic search of the PubMed database along with national agency databases-the Australian Institute of Health and Welfare (AIHW) and the Australian Bureau of Statistics (ABS).

RESULTS

A complex interplay between multiple factors contributes to the excess burden of IHD in the Indigenous Australian population: CONCLUSIONS: In terms of IHD, Indigenous Australians experience disadvantage at multiple stages of the disease process. Ongoing efforts are needed to continue to inform clinicians of both this disadvantage and strategies to assist negating it. Further research is needed to develop evidence based practices which may help reduce this disparity in outcomes.

Resting heart rate, physiological stress and disadvantage in Aboriginal and Torres Strait Islander Australians: analysis from a cross-sectional study

Background

Lower socioeconomic status has been linked to long-term stress, which can manifest in individuals as physiological stress. The aim was to explore the relationship between low socioeconomic status and physiological stress in Aboriginal and Torres Strait Islander Australians.

Methods

Using data from the eGFR Study (a cross-sectional study of 634 Indigenous Australians in urban and remote areas of northern and central Australia), we examined associations between resting heart rate and demographic, socioeconomic, and biomedical factors. An elevated resting heart rate has been proposed as a measure of sustained stress activation and was used as a marker of physiological stress. Relationships were assessed between heart rate and the above variables using univariate and multiple regression analyses.

Results

We reported a mean resting heart rate of 74 beats/min in the cohort (mean age 45 years). On multiple regression analysis, higher heart rate was found to be independently associated with Aboriginal ethnicity, being a current smoker, having only primary level schooling, higher HbA1c and higher diastolic blood pressure (model R² 0.25).

Conclusions

Elevated resting heart rate was associated with lower socioeconomic status and poorer health profile in Aboriginal and Torres Strait Islander Australians. Higher resting heart rate may be an indicator of stress and disadvantage in this population at high risk of chronic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0211-9) contains supplementary material, which is available to authorized users.

Periodontal disease and chronic kidney disease among Aboriginal adults; an RCT

BACKGROUND

This study will assess measures of vascular health and inflammation in Aboriginal Australian adults with chronic kidney disease (CKD), and determine if intensive periodontal intervention improves cardiovascular health, progression of renal disease and periodontal health over a 24-month follow-up.

METHODS

The study will be a randomised controlled trial. All participants will receive the periodontal intervention benefits, with the delayed intervention group receiving periodontal treatment 24 months following baseline. Inclusion criteria include being an Aboriginal Australian, having CKD (a. on dialysis; b. eGFR levels of < 60 mls/min/1.73 m(2) (CKD Stages 3 to 5); c. ACR ≥ 30 mg/mmol irrespective of eGFR (CKD Stages 1 and 2); d. diabetes plus albuminuria (ACR ≥ 3 mg/mmol) irrespective of eGFR), having moderate or severe periodontal disease, having at least 12 teeth, and living in Central Australia for the 2-year study duration. The intervention involves intensive removal of dental plaque biofilms by scaling, root-planing and removal of teeth that cannot be saved. The intervention will occur in three visits; baseline, 3-month and 6-month follow-up. The primary outcome will be changes in carotid intima-media thickness (cIMT). Secondary outcomes will include progression of CKD or death as a consequence of CKD/cardiovascular disease. Progression of CKD will be defined by time to the development of the first of: (1) new development of macroalbuminuria; (2) 30 % loss of baseline eGFR; (3) progression to end stage kidney disease defined by eGFR < 15 mLs/min/1.73 m(2); (4) progression to end stage kidney disease defined by commencement of renal replacement therapy. A sample size of 472 is necessary to detect a difference in cIMT of 0.026 mm (SD 0.09) at the significance criterion of 0.05 and a power of 0.80. Allowing for 20 % attrition, 592 participants are necessary at baseline, rounded to 600 for convenience.

DISCUSSION

This will be the first RCT evaluating the effect of periodontal therapy on progression of CKD and cardiovascular disease among Aboriginal patients with CKD. Demonstration of a significant attenuation of CKD progression and cardiovascular disease has the potential to inform clinicians of an important, new and widely available strategy for reducing CKD progression and cardiovascular disease for Australia's most disadvantaged population.

TRIAL REGISTRATION

This trial is registered with the Australian New Zealand Clinical Trial Registry ANZCTR12614001183673.

Effect of periodontal therapy on arterial structure and function among aboriginal australians: a randomized, controlled trial

Observational studies and nonrandomized trials support an association between periodontal disease and atherosclerotic vascular disease. Both diseases occur frequently in Aboriginal Australians. We hypothesized that nonsurgical periodontal therapy would improve measures of arterial function and structure that are subclinical indicators of atherosclerotic vascular disease. This parallel-group, randomized, open label clinical trial enrolled 273 Aboriginal Australians aged ≥18 years with periodontitis. Intervention participants received full-mouth periodontal scaling during a single visit, whereas controls received no treatment. Prespecified primary end points measured 12-month change in carotid intima-media thickness, an indicator of arterial structure, and 3- and 12-month change in pulse wave velocity, an indicator of arterial function. ANCOVA used complete case data to evaluate treatment group differences. End points could be calculated for 169 participants with follow-up data at 3 months and 168 participants at 12 months. Intima-media thickness decreased significantly after 12 months in the intervention group (mean reduction=-0.023 [95% confidence interval {CI}, -0.038 to -0.008] mm) but not in the control group (mean increase=0.002 [95% CI, -0.017 to 0.022] mm). The difference in intima-media thickness change between treatment groups was statistically significant (-0.026 [95% CI, -0.048 to -0.003] mm; P=0.03). In contrast, there were no significant differences between treatment groups in pulse wave velocity at 3 months (mean difference, 0.06 [95% CI, -0.17 to 0.29] m/s; P=0.594) or 12 months (mean difference, 0.21 [95% CI, -0.01 to 0.43] m/s; P=0.062). Periodontal therapy reduced subclinical arterial thickness but not function in Aboriginal Australians with periodontal disease, suggesting periodontal disease and atherosclerosis are significantly associated.

Closing the Gaps: competing estimates of Indigenous Australian life expectancy in the scientific literature

Objective: Closing the gap in life expectancy between Indigenous and other Australians within a generation is central to national Indigenous reform policy (Closing the Gap). Over time, various methods of estimating Indigenous life expectancy and with that, the life expectancy gap, have been adopted with differing, albeit non-comparable results. We present data on the extent of the gap and elucidate the pattern of use and interpretations of the different estimates of the gap, between 2007 and 2012.

Methods: An extensive search was conducted for all peer-reviewed health publications citing estimates of and/or discussing the life expectancy of Indigenous Australians, for the period 2007–2012.

Results: Five predominant patterns of citation of the gap estimates were identified: 20 years, 17 years, 15–20 years, 13 years, and 11.5 years for males and 9.7 years for females. Some authors misinterpret the most recent estimates as reflecting improvement from the 17-year figure, rather than the result of different methods of estimation. Support for the direct methods used to calculate Indigenous life expectancy is indicated.

Conclusions and Implications: A specific estimate of the life expectancy gap has not been established among stakeholders in Indigenous health. Agreement on the magnitude of the gap is arguably needed in order to evaluate strategies aimed at improving health outcomes for Indigenous Australians. Moreover, measuring progress towards ‘closing the gap’ depends on the availability of comparable estimates, using the same techniques of measurement to assess changes over time.

Stores Healthy Options Project in Remote Indigenous Communities (SHOP@RIC): a protocol of a randomised trial promoting healthy food and beverage purchases through price discounts and in-store nutrition education

BACKGROUND

Indigenous Australians suffer a disproportionate burden of preventable chronic disease compared to their non-Indigenous counterparts--much of it diet-related. Increasing fruit and vegetable intakes and reducing sugar-sweetened soft-drink consumption can reduce the risk of preventable chronic disease. There is evidence from some general population studies that subsidising healthier foods can modify dietary behaviour. There is little such evidence relating specifically to socio-economically disadvantaged populations, even though dietary behaviour in such populations is arguably more likely to be susceptible to such interventions.This study aims to assess the impact and cost-effectiveness of a price discount intervention with or without an in-store nutrition education intervention on purchases of fruit, vegetables, water and diet soft-drinks among remote Indigenous communities.

METHODS/DESIGN

We will utilise a randomised multiple baseline (stepped wedge) design involving 20 communities in remote Indigenous Australia. The study will be conducted in partnership with two store associations and twenty Indigenous store boards. Communities will be randomised to either i) a 20% price discount on fruit, vegetables, water and diet soft-drinks; or ii) a combined price discount and in-store nutrition education strategy. These interventions will be initiated, at one of five possible time-points, spaced two-months apart. Weekly point-of-sale data will be collected from each community store before, during, and for six months after the six-month intervention period to measure impact on purchasing of discounted food and drinks. Data on physical, social and economic factors influencing weekly store sales will be collected in order to identify important covariates. Intervention fidelity and mediators of behaviour change will also be assessed.

DISCUSSION

This study will provide original evidence on the effectiveness and cost-effectiveness of price discounts with or without an in-store nutrition education intervention on food and drink purchasing among a socio-economically disadvantaged population in a real-life setting.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry: ACTRN12613000694718.

Environmental risk conditions and pathways to cardiometabolic diseases in indigenous populations

This review examines environments in relation to cardiometabolic diseases in Indigenous populations in developed countries. Environmental factors are framed in terms of context (features of places) and composition (features of populations). Indigenous peoples are seen to have endured sociopolitical marginalization and material disadvantage spanning generations. Past adverse collective experiences, modified by culture, are reflected by current heterogeneity in environmental context and composition. As risk conditions, unfavorable contextual and compositional exposures influence the expression of cardiometabolic risk for individuals. Minimal research has evaluated heterogeneity in risk conditions against heterogeneity in cardiometabolic diseases between or within Indigenous populations. Thus far, the features of populations, not of places themselves, have been implicated in relation to cardiometabolic diseases. Behavioral, psychosocial, and stress-axis pathways may explain the relationships between risk conditions and cardiometabolic diseases. Implications of environmental factors and their pathways as well as important research needs are discussed in relation to ecological prevention to reduce cardiometabolic diseases.

High rates of albuminuria but not of low eGFR in urban indigenous Australians: the DRUID study

Background

Indigenous Australians have an incidence of end stage kidney disease 8-10 times higher than non-Indigenous Australians. The majority of research studies concerning Indigenous Australians have been performed in rural or remote regions, whilst the majority of Indigenous Australians actually live in urban settings. We studied prevalence and factors associated with markers of kidney disease in an urban Indigenous Australian cohort, and compared results with those for the general Australian population.

Methods

860 Indigenous adult participants of the Darwin Region Urban Indigenous Diabetes (DRUID) Study were assessed for albuminuria (urine albumin-creatinine ratio≥2.5 mg/mmol males, ≥3.5 mg/mmol females) and low eGFR (estimated glomular filtration rate < 60 mls/min/1.73 m²). Associations between risk factors and kidney disease markers were explored. Comparison was made with the AusDiab cohort (n = 8,936 aged 25-64 years), representative of the general Australian adult population.

Results

A high prevalence of albuminuria (14.8%) was found in DRUID, whilst prevalence of low eGFR was 2.4%. Older age, higher HbA1c, hypertension, higher C-reactive protein and current smoking were independently associated with albuminuria on multiple regression. Low eGFR was independently associated with older age, hypertension, albuminuria and higher triglycerides. Compared to AusDiab participants, DRUID participants had a 3-fold higher adjusted risk of albuminuria but not of low eGFR.

Conclusions

Given the significant excess of ESKD observed in Indigenous versus non-Indigenous Australians, these findings could suggest either: albuminuria may be a better prognostic marker of kidney disease than low eGFR; that eGFR equations may be inaccurate in the Indigenous population; a less marked differential between Indigenous and non-Indigenous Australians for ESKD rates in urban compared to remote regions; or that differences in the pathophysiology of chronic kidney disease exist between Indigenous and non-Indigenous populations.

Environments and cardiometabolic diseases in aboriginal populations

This review establishes the relevance and frames the relationship of environmental factors to cardiometabolic risk factors and disease in Aboriginal populations. Environmental factors operate at the level of communities or populations. They include contextual measures of places and compositional measures of populations which together constitute "risk conditions" affecting individual risk factors. Environmental factors have been implicated by contrasting Aboriginal and non-Aboriginal populations in cardiometabolic risk factors and outcomes, or by geographic contrasts of Aboriginal populations in remote, rural and urban regions. It is unclear whether heterogeneity in contextual or compositional factors between and within Aboriginal populations is associated with heterogeneity in cardiometabolic risk factors and outcomes. Empirical literature that links environmental factors and cardiometabolic outcomes in Aboriginal populations is critically reviewed for three postulated pathways of influence: (1) behaviour; (2) psychosocial factors; and (3) stress response axes. These pathways, represented as interdependent, can explain how and why environments are associated with cardiometabolic outcomes. The need remains, however, to develop a robust quantitative evidence base in cardiometabolic research aimed at enhancing knowledge of the specific environmental factors related to the cardiometabolic health of Aboriginal populations as well as explicating the underlying mechanisms by which environmental risk conditions 'get under the skin'.

The metabolic syndrome and its traits as risk factors for subclinical atherosclerosis

CONTEXT AND OBJECTIVE

The metabolic syndrome (MetS) indicates an increased cardiovascular risk. The objective of the present study was to determine the impact of the MetS and its individual traits on subclinical atherosclerosis, as measured with six noninvasive measurements of atherosclerosis (NIMA) in a 50- to 70-yr-old Dutch population-based cohort. Furthermore, we determined the impact of three different definitions of the MetS.

DESIGN

We performed NIMA in 1517 participants of the Nijmegen Biomedical Study. The MetS was defined by definitions of the National Cholesterol Education Program, International Diabetes Federation, and the World Health Organization.

RESULTS

Participants with the MetS (National Cholesterol Education Program) were characterized by increased subclinical atherosclerosis compared with participants without any trait of the MetS, as reflected by lower ankle-brachial index at rest [percent change (95% confidence interval), M: -5.2% (-9; -1), F: -3.1% (-6; -1)] and after exercise [M: -7.7% (-17;+2), F: -6.6% (-11; -2)], higher augmentation index [M: +4.8% (+3; +7), F: +1.9% (+4; +18)], increased pulse wave velocity [M: +22.8% (+15;+32), F: +20.5% (+14; +28)], increased intima-media thickness [M: +9.3% (+5; +13), F: +6.9% (+3; +11)], and thicker plaques [M: +17.6% (-2; +41), F: +26.6% (+5; +53)]. Most intriguingly, the number of traits was strongly associated with the severity of subclinical atherosclerosis because all NIMA gradually deteriorated with increasing number of traits present; NIMA were already deteriorated when one or two traits were present and further deteriorated when four or five traits of the MetS were present. Similar result were found when International Diabetes Federation and World Health Organization definitions of the MetS were used.

CONCLUSIONS

For cardiovascular risk prediction, it is more important to take into account the presence of each individual trait and the number of traits of the MetS than to diagnose the presence of the MetS.

Risk factors for cardiovascular disease do not fully explain differences in carotid intima-media thickness between Indigenous and European Australians without diabetes

OBJECTIVE

To investigate whether cardiovascular risk factors can explain the higher carotid intima-media thickness (CIMT) in Indigenous compared with European Australians.

DESIGN

Cross-sectional study in three subgroups.

PATIENTS

Non-diabetic urban European (n = 86), urban Indigenous (n = 69), and remote Indigenous (n = 60) Australians aged 25-64 years.

MEASUREMENTS

CIMT, age, sex, anthropometry, blood pressure, smoking status, fasting glucose and insulin, haemoglobin (Hb)A1c, homocysteine, C-reactive protein (CRP), lipids, urinary albumin and creatinine.

RESULTS

CIMT and levels of risk factors, except fasting glucose and total cholesterol, worsened across the three groups. Log(n) fasting insulin [beta = 0.022, 95% confidence interval (CI) 0-0.0439], age (beta = 0.006, 95% CI 0.004-0.007), gender (female beta = -0.005 vs. male, 95% CI -0.084 to -0.026), mean arterial pressure (MAP) (beta = 0.001, 95% CI 0.001-0.002) and ethnicity/location [urban Indigenous (beta = 0.027, 95% CI -0.010 to 0.064 vs. European); remote Indigenous (beta = 0.083, 95% CI 0.042-0.123 vs. European)] explained 41% of variance in CIMT. Significant interactions were seen for ethnicity/location with age (P = 0.014) and MAP (P = 0.018). Age was consistently associated with CIMT across the three populations, and was associated with larger increments in CIMT for the Indigenous subgroups (beta = 0.007, 95% CI 0.005-0.009 urban; beta = 0.007, 95% CI 0.004-0.010 remote) compared with Europeans (beta = 0.003, 95% CI 0.002-0.006) in models including age, sex and MAP. MAP was only associated with CIMT in the remote Indigenous subgroup.

CONCLUSION

After adjusting for selected risk factors, CIMT in remote Indigenous participants was still higher than in Europeans. The slope of the association between age and CIMT steepened from urban Europeans to remote Indigenous.

Impact of dyslipidaemia on arterial structure and function in urban indigenous Australians

BACKGROUND

Premature cardiovascular disease (CDV) is highly prevalent in urban Indigenous Australians. We studied arterial structure and function in 144 volunteers aged 15-66 years to assess the role of dyslipidaemia and other traditional vascular risk factors on cardiovascular risk in young and older urban Indigenous Australians.

METHODS

We assessed carotid intima-media thickness (CIMT) by high-resolution B-mode ultrasound imaging of the common carotid artery and peripheral wave reflection using applanation tonometry to obtain the aortic augmentation index (AI) in Indigenous Australian participants of the Darwin Region Urban Indigenous Diabetes (DRUID) study.

RESULTS

Participants aged 15-24 years demonstrated fewer cardiovascular risk factors than the older group (25-66 years) and predictors of CIMT and AI differed between younger and older groups. CIMT was higher in the older group (0.67mm vs. 0.61mm, p=0.004) and in those with diabetes (0.81mm vs. 0.67mm, p<0.001). AI was higher in the older group (24% vs. 0%, p<0.001), but was not affected by diabetes status. On multivariate regression analysis, low HDL-cholesterol was the only independent predictor of CIMT in the younger group; triglycerides, heart rate (inverse) and height (inverse) were independent predictors of AI in the same group.

CONCLUSION

Dyslipidaemia (low HDL-cholesterol or elevated triglycerides) is independently associated with non-invasive measures of cardiovascular disease in a relatively healthy and young subgroup of this high-risk population. We propose that triglycerides and low HDL-cholesterol may represent the most useful commonly measured clinical indicators of cardiovascular risk in young, urban Indigenous Australians.

Metabolic syndrome is not associated with reduction in aortic distensibility in subjects with type 2 diabetes mellitus

BACKGROUND

Aortic distensibility (AD) is a marker of the elastic properties of the aorta. Reduction of AD occurs early in subjects with type 2 diabetes mellitus (T2DM) and it is associated with subclinical generalized atherosclerosis. Metabolic syndrome (MetS) is common in subjects with T2DM and predicts cardiovascular morbidity and mortality. This study examined the potential relationship between MetS and AD in a cohort of subjects with T2DM.

METHODS AND RESULTS

A total of 210 subjects with T2DM were studied. MetS was diagnosed using the NCEP/ATP-III criteria. AD was assessed non-invasively by ultrasonography. The prevalence of MetS was 64.8%. AD was not significantly different between subjects with and without MetS (1.80 +/- 0.54 vs. 1.84 +/- 0.53 10-6 dyn-1 cm2, p = 0.55). Univariate linear regression analysis showed that AD was associated positively with male sex (p = 0.02) as well as glomerular filtration rate (p < 0.001), and negatively with age (p = 0.04), history of hypertension (p = 0.001), as well as duration of diabetes (p < 0.001). After multivariate adjustment, AD was associated independently and significantly only with age (p = 0.02), duration of diabetes p < 0.001), and history of hypertension (p = 0.004); no significant relationship was found with MetS status, the sum of the components of the MetS or the individual components-besides hypertension-of the MetS.

CONCLUSION

In subjects with T2DM, MetS status per se is not associated with reduction of AD. In addition, it was shown that besides ageing, duration of glycemia was a strong predictor of AD. From the components of the MetS only hypertension was associated with reduction of the elastic properties of the aorta.

High-sensitivity C-reactive protein predicts target organ damage in Chinese patients with metabolic syndrome

Observational studies established high-sensitivity C-reactive protein as a risk factor for cardiovascular events in the general population. The goal of this study was to determine the relationship between target organ damage and high-sensitivity C-reactive protein in a cohort of Chinese patients with metabolic syndrome. A total of 1082 consecutive patients of Chinese origin were screened for the presence of metabolic syndrome according to the National Cholesterol Education Program's Adult Treatment Panel III. High-sensitivity C-reactive protein and target organ damage, including cardiac hypertrophy, carotid intima-media thickness, and renal impairment, were investigated. The median (25th and 75th percentiles) of high-sensitivity C-reactive protein in 619 patients with metabolic syndrome was 2.42 mg/L (0.75 and 3.66 mg/L) compared with 1.13 mg/L (0.51 and 2.46 mg/L) among 463 control subjects (P < .01). There was a progressive increase in high-sensitivity C-reactive protein level with the number of components of the metabolic syndrome. Stratification of patients with metabolic syndrome into 3 groups according to their high-sensitivity C-reactive protein concentrations (<1.0, 1.0-3.0, and >3.0 mg/L) showed that the subjects with the elevated high-sensitivity C-reactive protein had a higher percentage of target organ damage than those with lower high-sensitivity C-reactive protein. Stepwise multiple logistic regression confirmed that high-sensitivity C-reactive protein was significantly associated with cardiac hypertrophy, carotid intima-media thickness, and renal impairment. The study shows a strong independent association between inflammation and target organ damage in a large cohort of patients of Chinese origin with metabolic syndrome.