Haemostatic Variables in Pacific Islanders Apparently Free from Stroke and Ischaemic Heart Disease – The Kitava Study

Stroke Epidemiology in Oceania: A Review

BACKGROUND AND PURPOSE

Oceania, comprising the regions Australasia, Melanesia, Micronesia, and Polynesia, is home to 42 million living in 8.5 million square kilometres of land. This paper comprises a review of the epidemiology of stroke in countries in this region.

METHODS

Information on epidemiology of stroke in Oceania was sought from data from the Global Burden of Disease (GBD) study (incidence, mortality, incidence:mortality ratio [IMR], prevalence, disability-adjusted life-years [DALYs] lost due to stroke, and subtypes), World Health Organization (WHO) (vascular risk factors in the community), and PubMed (incidence, prevalence, and stroke subtypes). Data were analyzed by region to allow inter-country comparison within each region.

RESULTS

In 2010, age- and sex-standardized stroke mortality rates were lowest in Australasia (29.85-31.67/100,000) and highest in Melanesia and Micronesia (56.04-187.56/100,000), with wide ranges especially in Melanesia. Incidence rates were lowest in Australasia (101.36-105.54/100,000), similarly high elsewhere. Standardized IMR (0.98-3.39) was the inverse of the mortality rates and mirrored the prevalence rates (202.91-522.29/100,000). DALY rates (398.22-3,781.78/100,0000) mirrored the mortality rates. Stroke risk factors show a variable pattern - hypertension is generally the most common medical risk factor among males (18.0-26.6%), while among females, diabetes mellitus is the most common in Micronesia and Polynesia (21.5-28.4%). Among the lifestyle factors, current smoking is the most common in Melanesia among males, while obesity is generally the most common factor among females. Ischaemic stroke comprises 70% of stroke subtypes. Trend data show significant falls in standardized mortality rates and DALYs in most regions and falls in incidence in almost all countries. There is significant economic impact, particularly due to young strokes; some ethnicities are at higher risk than others, for example, Maoris and Pacific Islanders.

CONCLUSIONS

Stroke is a major healthcare problem in Oceania. Variations in stroke epidemiology are found between countries in Oceania. Data are lacking in some; more research into the burden of stroke in Oceania is needed. With the expected increase in life expectancy and vascular risk factors, the burden of stroke in Oceania will likely rise. Some of the disparities in stroke burden may be addressed by great investment in healthcare.

C-reactive protein in traditional melanesians on Kitava

Background

Population-based levels of the chronic low-grade systemic inflammation biomarker, C-reactive protein (CRP), vary widely among traditional populations, despite their apparent absence of chronic conditions associated with chronic low-grade systemic inflammation, such as type 2 diabetes, metabolic syndrome and cardiovascular disease. We have previously reported an apparent absence of aforementioned conditions amongst the traditional Melanesian horticulturalists of Kitava, Trobriand Islands, Papua New Guinea. Our objective in this study was to clarify associations between chronic low-grade systemic inflammation and chronic cardiometabolic conditions by measuring CRP in a Kitava population sample. For comparison purposes, CRP was also measured in Swedish controls matched for age and gender.

Methods

Fasting levels of serum CRP were measured cross-sectionally in ≥ 40-year-old Kitavans (N = 79) and Swedish controls (N = 83).

Results

CRP was lower for Kitavans compared to Swedish controls (Mdn 0.5 mg/L range 0.1—48 mg/L and Mdn 1.1 mg/L range 0.1—33 mg/L, respectively, r = .18 p = .02). Among Kitavans, there were small negative associations between lnCRP for CRP values < 10 and total, low-density lipoprotein (LDL) and non-high-density lipoprotein (non-HDL) cholesterol. Among Swedish controls, associations of lnCRP for CRP values < 10 were medium positive with weight, body mass index, waist circumference, hip circumference and waist-hip ratio and low positive with triglyceride, total cholesterol-HDL cholesterol ratio, triglyceride-HDL cholesterol ratio and serum insulin.

Conclusions

Chronic low-grade systemic inflammation, measured as CRP, was lower among Kitavans compared to Swedish controls, indicating a lower and average cardiovascular risk, respectively, for these populations.

Genome-nutrition divergence: evolving understanding of the malnutrition spectrum

Humans adapted over a period of 2.3 million years to a diet high in quality and diversity. Genome-nutrition divergence describes the misalignment between modern global diets and the genome formed through evolution. A survey of hominin diets over time shows that humans have thrived on a broad range of foods. Earlier diets were highly diverse and nutrient dense, in contrast to modern food systems in which monotonous diets of staple cereals and ultraprocessed foods play a more prominent role. Applying the lens of genome-nutrition divergence to malnutrition reveals shared risk factors for undernutrition and overnutrition at nutrient, food, and environmental levels. Mechanisms for food system shifts, such as crop-neutral agricultural policy, agroecology, and social policy, are explored as a means to realign modern diets with the nutritional patterns to which humans may be better adapted to thrive.

Cardiovascular disease and type 2 diabetes in evolutionary perspective: a critical role for helminths?

Heart disease and type 2 diabetes are commonly believed to be rare among contemporary subsistence-level human populations, and by extension prehistoric populations. Although some caveats remain, evidence shows these diseases to be unusual among well-studied hunter-gatherers and other subsistence populations with minimal access to healthcare. Here we expand on a relatively new proposal for why these and other populations may not show major signs of these diseases. Chronic infections, especially helminths, may offer protection against heart disease and diabetes through direct and indirect pathways. As part of a strategy to insure their own survival and reproduction, helminths exert multiple cardio-protective effects on their host through their effects on immune function and blood lipid metabolism. Helminths consume blood lipids and glucose, alter lipid metabolism, and modulate immune function towards Th-2 polarization - which combined can lower blood cholesterol, reduce obesity, increase insulin sensitivity, decrease atheroma progression, and reduce likelihood of atherosclerotic plaque rupture. Traditional cardiometabolic risk factors, coupled with the mismatch between our evolved immune systems and modern, hygienic environments may interact in complex ways. In this review, we survey existing studies in the non-human animal and human literature, highlight unresolved questions and suggest future directions to explore the role of helminths in the etiology of cardio-metabolic disease.

A sequence variation scan of the coagulation factor VIII (FVIII) structural gene and associations with plasma FVIII activity levels

Plasma factor VIII coagulant activity (FVIII:C) level is a highly heritable quantitative trait that is strongly correlated with thrombosis risk. Polymorphisms within only 1 gene, the ABO blood-group locus, have been unequivocally demonstrated to contribute to the broad population variability observed for this trait. Because less than 2.5% of the structural FVIII gene (F8) has been examined previously, we resequenced all known functional regions in 222 potentially distinct alleles from 137 unrelated nonhemophilic individuals representing 7 racial groups. Eighteen of the 47 variants identified, including 17 single-nucleotide polymorphisms (SNPs), were previously unknown. As the degree of linkage disequilibrium across F8 was weak overall, we used measured-genotype association analysis to evaluate the influence of each polymorphism on the FVIII:C levels in 398 subjects from 21 pedigrees known as the Genetic Analysis of Idiopathic Thrombophilia project (GAIT). Our results suggested that 92714C>G, a nonsynonymous SNP encoding the B-domain substitution D1241E, was significantly associated with FVIII:C level. After accounting for important covariates, including age and ABO genotype, the association persisted with each C-allele additively increasing the FVIII:C level by 14.3 IU dL(-1) (P = .016). Nevertheless, because the alleles of 56010G>A, a SNP within the 3' splice junction of intron 7, are strongly associated with 92714C>G in GAIT, additional studies are required to determine whether D1241E is itself a functional variant.

Serum uric acid in traditional Pacific Islanders and in Swedes

BACKGROUND

In some western populations, increased serum uric acid has been positively associated with cardiovascular disease, possibly because hyperuricaemia could be an untoward part of the insulin-resistant metabolic syndrome. However, there is evidence that uric acid is a free radical scavenger capable of inhibiting LDL oxidation. Amongst the traditional horticulturalists of Kitava, Trobriand Islands, Papua New Guinea, cardiovascular disease, hypertension, hyperinsulinaemia and abdominal obesity are absent or rare. In contrast, serum triglycerides are similar to Swedish levels.

OBJECTIVE

To compare serum uric acid between nonwesternized and westernized populations.

METHODS

Fasting levels of serum uric acid were measured cross-sectionally in 171 Kitavans aged 20-86 years and in 244 randomly selected Swedish subjects aged 20-80 years.

RESULTS

There were small differences in serum uric acid between the two populations, although a slight increase with age was found only in Swedish males (r = 0.20; P = 0.03) and females (r = 0.36; P < 0.0001). Above 40 years of age, uric acid was approximately 10% lower in Kitavans, a difference which was statistically significant only in males, possibly because of the limited number of females. Regarding hyperuricaemia, two Kitavan males had uric acid above 450 micromol L-1 whilst none of the females was above 340 micromol L-1. Amongst the Swedish subjects, five of 117 males and 19 of 127 females had hyperuricaemia according to these definitions.

CONCLUSION

The rather similar uric acid levels between Kitava and Sweden imply that uric acid is of minor importance to explain the apparent absence of cardiovascular disease in Kitava.

Large differences in serum leptin levels between nonwesternized and westernized populations: the Kitava study

OBJECTIVES

To compare serum leptin between nonwesternized and westernized populations.

SETTING

(i) The tropical island of Kitava, Trobriand Islands, Papua New Guinea and (ii) the Northern Sweden MONICA study population. Design. Cross-sectional survey.

METHODS

Fasting levels of serum leptin were analysed in 163 randomly selected Kitavans aged 20-86 years and in 224 Swedes aged 25-74.

MAIN OUTCOME MEASURE

Mean and determinants of serum leptin.

RESULTS

Geometric mean of serum leptin in Kitavan males and females were 1.5 and 4.0 vs. 4.9 and 13.8 ng mL-1 in Swedish male and females (P < 0.0001 for both sexes). In Kitavans, observed geometric mean were close to predicted levels (1.8 ng mL(-1) for males and 4.5 ng mL-1 for females) based on multiple linear regression equations including body mass index (BMI), triceps skinfolds (TSF) and age from the Swedish population-based sample. In Kitavans serum leptin was positively related to TSF amongst both sexes and, amongst females, to BMI. In Kitavans leptin was not related to fasting serum insulin. TSF explained 55% of the variation of leptin amongst females. There was a slight age-related increase of leptin amongst males. In Kitava leptin was not related to fasting serum insulin which was substantially lower than in Sweden.

CONCLUSION

The low concentrations of serum leptin amongst Kitavans probably relates to the absence of overweight and hyperinsulinaemia. At a population level serum leptin can apparently be predicted from simple measures of adiposity.