Relationship between plasma glucose concentrations and Native Hawaiian Ancestry: The Native Hawaiian Health Research Project

Interethnic differences in pancreatic cancer incidence and risk factors: The Multiethnic Cohort

While disparity in pancreatic cancer incidence between blacks and whites has been observed, few studies have examined disparity in other ethnic minorities. We evaluated variations in pancreatic cancer incidence and assessed the extent to which known risk factors account for differences in pancreatic cancer risk among African Americans, Native Hawaiians, Japanese Americans, Latino Americans, and European Americans in the Multiethnic Cohort Study. Risk factor data were obtained from the baseline questionnaire. Cox regression was used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) for pancreatic cancer associated with risk factors and ethnicity. During an average 16.9-year follow-up, 1,532 incident pancreatic cancer cases were identified among 184,559 at-risk participants. Family history of pancreatic cancer (RR 1.97, 95% CI 1.50-2.58), diabetes (RR 1.32, 95% CI 1.14-1.54), body mass index ≥30 kg/m² (RR 1.25, 95% CI 1.08-1.46), current smoking (<20 pack-years RR 1.43, 95% CI 1.19-1.73; ≥20 pack-years RR 1.76, 95% CI 1.46-2.12), and red meat intake (RR 1.17, 95% CI 1.00-1.36) were associated with pancreatic cancer. After adjustment for these risk factors, Native Hawaiians (RR 1.60, 95% CI 1.30-1.98), Japanese Americans (RR 1.33, 95% CI 1.15-1.54), and African Americans (RR 1.20, 95% CI 1.01-1.42), but not Latino Americans (RR 0.90, 95% CI 0.76-1.07), had a higher risk of pancreatic cancer compared to European Americans. Interethnic differences in pancreatic cancer risk are not fully explained by differences in the distribution of known risk factors. The greater risks in Native Hawaiians and Japanese Americans are new findings and elucidating the causes of these high rates may improve our understanding and prevention of pancreatic cancer.

Ethnic admixture affects diabetes risk in native Hawaiians: the Multiethnic Cohort

BACKGROUND/OBJECTIVES

Obesity and diabetes rates are high in Native Hawaiians (NHs) who commonly have mixed ancestries. People of Asian ancestry experience a high risk of type 2 diabetes despite the relatively low body weight. We evaluated the impact of ethnic admixture on diabetes risk among NHs in the Multiethnic Cohort (MEC).

SUBJECTS/METHODS

On the basis of self-reports, 11 521 eligible men and women were categorized into NH/white, NH/other, NH alone, NH/Asian and the most common three ancestry admixture, NH/Chinese/white. Cox proportional hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated with the NH/white category as the reference group; covariates included known confounders-that is, body mass index (BMI), dietary and other lifestyle factors.

RESULTS

The NH alone category had the highest proportion of overweight and obese individuals and the NH/Asian category the lowest proportion. During 12 years of follow-up after cohort entry at 56 years, 2072 incident cases were ascertained through questionnaires and health plan linkages. All NH categories had higher HRs than the NH/white category before and after adjustment for BMI. In the fully adjusted models, the NH/Asian category showed the highest risk (HR=1.45; 95% CI: 1.27-1.65), followed by NH/other (HR=1.20; 95% CI: 1.03-1.39), NH/Chinese/white (HR=1.19; 95% CI: 1.04-1.37) and NH alone (HR=1.19; 95% CI: 1.03-1.37). The elevated risk by Asian admixture was more pronounced in normal weight than overweight/obese individuals.

CONCLUSIONS

These findings indicate that Asian admixture in NHs is associated with a higher risk for type 2 diabetes independent of known risk factors and suggest a role for ethnicity-related genetic factors in the development of this disease.

Nutrition and Diet as It Relates to Health and Well-Being of Native Hawaiian Kūpuna (Elders): A Systematic Literature Review

PURPOSE

The key to improving the health and well-being of Native Hawaiians is to understand the historical events that have caused change to their diet and nutrition, and identify the connection between food, life, and the land. The purpose of this article is to (a) present a review of the literature addressing nutrition and diet as it relates to health and well-being of Native Hawaiian kūpuna (elders) and (b) identify limitations and gaps to promote future research.

DESIGN

This systematic literature review focused on 29 studies.

FINDINGS

Native Hawaiians have the highest body mass index levels, highest daily energy (kilocalorie) intake, and lowest multivitamin use. They have the highest prevalence of diabetes and hypertension compared with Whites. Traditional Hawaiian diet programs and family support were beneficial to improving health and well-being.

CONCLUSION

Future research of traditional Hawaiian diet programs and revitalization of the culture may lead to improving the health and well-being of Native Hawaiians.

Disparity in diabetes risk across Native Hawaiians and different Asian groups: the multiethnic cohort

We evaluated the impact of body mass index (BMI) and lifestyle risk factors on ethnic disparity in diabetes incidence among 89 198 Asian, Native Hawaiian, and white participants of the Multiethnic Cohort who completed multiple questionnaires. After 12 years of follow-up, 11 218 new cases were identified through self-report and health plan linkages. BMI was lowest in Chinese/Koreans, Japanese, and Filipinos (22.4, 23.5, and 23.9 kg/m(2)). Using Cox regression, the unadjusted hazard ratios were 1.9 (Chinese/Korean), 2.1 (Japanese, Mixed-Asian), 2.2 (Filipino), 2.5 (Native Hawaiian), and 2.6 (part-Asian) as compared with whites. With BMI added, the risk for Japanese, Filipinos, Chinese/Koreans, and mixed-Asians increased (8%-42%) but declined in part-Asians and Native Hawaiians (17%-31%). When lifestyle and dietary factors were also included, the risk was attenuated in all groups (6%-14%). Despite their lower BMI, Asian Americans have a higher diabetes risk than whites, but dietary and lifestyle factors do not account for the excess risk.

Self-reported ethnicity, genetic structure and the impact of population stratification in a multiethnic study

It is well-known that population substructure may lead to confounding in case-control association studies. Here, we examined genetic structure in a large racially and ethnically diverse sample consisting of five ethnic groups of the Multiethnic Cohort study (African Americans, Japanese Americans, Latinos, European Americans and Native Hawaiians) using 2,509 SNPs distributed across the genome. Principal component analysis on 6,213 study participants, 18 Native Americans and 11 HapMap III populations revealed four important principal components (PCs): the first two separated Asians, Europeans and Africans, and the third and fourth corresponded to Native American and Native Hawaiian (Polynesian) ancestry, respectively. Individual ethnic composition derived from self-reported parental information matched well to genetic ancestry for Japanese and European Americans. STRUCTURE-estimated individual ancestral proportions for African Americans and Latinos are consistent with previous reports. We quantified the East Asian (mean 27%), European (mean 27%) and Polynesian (mean 46%) ancestral proportions for the first time, to our knowledge, for Native Hawaiians. Simulations based on realistic settings of case-control studies nested in the Multiethnic Cohort found that the effect of population stratification was modest and readily corrected by adjusting for race/ethnicity or by adjusting for top PCs derived from all SNPs or from ancestry informative markers; the power of these approaches was similar when averaged across causal variants simulated based on allele frequencies of the 2,509 genotyped markers. The bias may be large in case-only analysis of gene by gene interactions but it can be corrected by top PCs derived from all SNPs.

Admixture mapping comes of age

Admixture mapping is based on the hypothesis that differences in disease rates between populations are due in part to frequency differences in disease-causing genetic variants. In admixed populations, these genetic variants occur more often on chromosome segments inherited from the ancestral population with the higher disease variant frequency. A genome scan for disease association requires only enough markers to identify the ancestral chromosome segments; for recently admixed populations, such as African Americans, 1,500-2,500 ancestry-informative markers (AIMs) are sufficient. The method was proposed over 50 years ago, but the AIM panels and statistical methods required have only recently become available. Since the first admixture scan in 2005, the genetic bases for a range of diseases/traits have been identified by admixture mapping. Here, we provide a historical perspective, review AIM panels and software packages, and discuss recent successes and unexpected insights into human diseases that exhibit disparate rates across human populations.

Diabetes incidence based on linkages with health plans: the multiethnic cohort

OBJECTIVE

Using the Hawaii component of the Multiethnic Cohort (MEC), we estimated diabetes incidence among Caucasians, Japanese Americans, and Native Hawaiians.

RESEARCH DESIGN AND METHODS

After excluding subjects who reported diabetes at baseline or had missing values, 93,860 cohort members were part of this analysis. New case subjects were identified through a follow-up questionnaire (1999-2000), a medication questionnaire (2003-2006), and linkage with two major health plans (2007). We computed age-standardized incidence rates and estimated hazard ratios (HRs) for ethnicity, BMI, education, and combined effects of these variables using Cox regression analysis.

RESULTS

After a total follow-up time of 1,119,224 person-years, 11,838 incident diabetic case subjects were identified with an annual incidence rate of 10.4 per 1,000 person-years. Native Hawaiians had the highest rate with 15.5, followed by Japanese Americans with 12.5, and Caucasians with 5.8 per 1,000 person-years; the adjusted HRs were 2.65 for Japanese Americans and 1.93 for Native Hawaiians. BMI was positively related to incidence in all ethnic groups. Compared with the lowest category, the respective HRs for BMIs of 22.0-24.9, 25.0-29.9, and > or =30.0 kg/m(2) were 2.10, 4.12, and 9.48. However, the risk was highest for Japanese Americans and intermediate for Native Hawaiians in each BMI category. Educational achievement showed an inverse association with diabetes risk, but the protective effect was limited to Caucasians.

CONCLUSIONS

Within this multiethnic population, diabetes incidence was twofold higher in Japanese Americans and Native Hawaiians than in Caucasians. The significant interaction of ethnicity with BMI and education suggests ethnic differences in diabetes etiology.

Effects of ethnicity and socioeconomic status on body composition in an admixed, multiethnic population in Hawaii

This study determined ethnic differences in anthropometric measures of a sample of adults in Hawaii, examining the effects of differing degrees of ethnic admixing and socioeconomic status (SES) on the measures. Adults who had attended elementary school in Hawaii underwent anthropometric measurements and answered questionnaires about their educational attainment, income, age, cultural identity, ethnic ancestry, and health. Individuals reporting Asian American cultural identity had significantly lower mean body mass index (BMI) and waist circumference (WC) than others, whereas those with Hawaiian/Pacific Islander cultural identity had significantly higher BMI and WC. Educational attainment, but not reported family income and age, was significantly related to BMI and WC, and differences in educational attainment accounted for the increased mean BMI and WC in Hawaiian/Pacific Islanders, but did not account for the lower mean BMI and WC among Asian Americans. Higher percentage of Asian ancestry was significantly correlated with lower BMI and WC, whereas higher percentage of Hawaiian/Pacific Islander ancestry was significantly correlated with increased BMI and WC. Differences in education accounted for the significantly increased BMI in participants with a higher percentage of Hawaiian/Pacific Islander ancestry, but did not entirely account for the lower BMI in individuals with a higher percentage of Asian American ancestry. These results suggest that the high rate of obesity and its sequelae seen in Pacific Islanders may be more a result of socioeconomic status and lifestyle than of genetic propensity, whereas the lower rates of obesity observed in Asian American populations are less directly influenced by socioeconomic factors.

Cardiometabolic health disparities in native Hawaiians and other Pacific Islanders

Elimination of health disparities in the United States is a national health priority. Cardiovascular disease, diabetes, and obesity are key features of what is now referred to as the "cardiometabolic syndrome," which disproportionately affects racial/ethnic minority populations, including Native Hawaiians and other Pacific Islanders (NHOPI). Few studies have adequately characterized the cardiometabolic syndrome in high-risk populations such as NHOPI. The authors systematically assessed the existing literature on cardiometabolic disorders among NHOPI to understand the best approaches to eliminating cardiometabolic health disparities in this population. Articles were identified from database searches performed in PubMed and MEDLINE from January 1998 to December 2008; 43 studies were included in the review. There is growing confirmatory evidence that NHOPI are one of the highest-risk populations for cardiometabolic diseases in the United States. Most studies found increased prevalences of diabetes, obesity, and cardiovascular risk factors among NHOPI. The few experimental intervention studies found positive results. Methodological issues included small sample sizes, sample bias, inappropriate racial/ethnic aggregation of NHOPI with Asians, and a limited number of intervention studies. Significant gaps remain in the understanding of cardiometabolic health disparities among NHOPI in the United States. More experimental intervention studies are needed to examine promising approaches to reversing the rising tide of cardiometabolic health disparities in NHOPI.

Major dietary patterns, ethnicity, and prevalence of type 2 diabetes in rural Hawaii

OBJECTIVE

The association of type 2 diabetes (T2DM) with the overall dietary pattern and its relation with ethnicity was examined.

METHODS

A cross-sectional study with 1257 participants with four ethnicities (Caucasian, Filipino, Native Hawaiian, and Japanese) in the North Kohala region of Hawaii was conducted. Participants 18-95 y of age were surveyed for their ethnic and demographic backgrounds, dietary intakes, and biochemical indexes of glucose intolerance between 1997 and 2000.

RESULTS

Three dietary patterns from the food-frequency questionnaire were identified by factor analysis. Factor 1 was characterized by a healthy diet with a frequent intake of vegetables and fruits, and factor 2 was dominated by animal foods and local ethnic dishes. Factor 3 was characterized by a Western diet, which was dominated by French fries, fast-food hamburgers, pizza, and chips. Multivariate logistic regression model for T2DM prevalence included ethnicity and three dietary factors after adjustment for age, sex, income, physical activity, smoking status, and energy intake. Ethnicity was significantly associated with T2DM, with an odds ratio of 1.83 (95% confidence interval [CI] 1.12-3.00) for Native Hawaiians and 1.92 (95% CI 1.12-3.29) for Filipinos compared with Caucasians 1.92 (95% CI 1.12-3.29). Among the three dietary factors, factor 2 was positively associated with T2DM (odds ratio 1.30, 95% CI 1.03-1.68), but the significance disappeared after adjustment for energy intake.

CONCLUSION

The findings show that ethnicity is a stronger risk factor for T2DM than dietary patterns when energy intake is adjusted for. Reducing energy intake to prevent T2DM deserves more attention during health promotion for the multiethnic population of Hawaii.

Cancer assessment methodology in a native Hawaiian community

BACKGROUND

Limited data have been collected on cancer in Native Hawaiian communities, although Native Hawaiians tend to have higher cancer mortality rates than other ethnic groups in Hawaii.

OBJECTIVES

We sought to describe the community-based participatory research (CBPR) process used to deliver a culturally tailored protocol, combining traditional Native Hawaiian practices and random sampling methods, to determine cancer screening practices and program preferences of residents of a Hawaiian Homes (HH) community.

METHODS

Following a culturally tailored protocol, we attempted to survey half of the 644 households in the Waimanalo Hawaiian Homes Community (WHHC). Pairs of Native Hawaiian college students performed the majority of data collection; a community member joined them if available. Visits to the selected homes were tracked and participation rates estimated. Additional information on this methodology emerged from discussions between researchers and community members.

RESULTS

Of the 449 households accessed, 187 (42%) completed the survey, with an average of two visits per household. Individuals at 63 (14%) households refused outright. The remaining 199 (44%) homes were visited up to five times, but produced no response. Although some homes were vacant, often it appeared that residents were home but unresponsive. Our sampling procedure (targeting every other house and requiring accrual of 75 individuals in each of four age-gender groups) reduced participation.

CONCLUSIONS

The use of CBPR built capacity for all partners by engaging them in all levels of research. The results, however, suggest the need for a more inclusive sampling strategy and the continued use of CBPR.

Hyperglycemia and type 2 diabetes among Filipino women in the Philippines, Hawaii, and San Diego

BACKGROUND

Diabetes risk increases as immigrant populations adopt western lifestyles. We compared the prevalence of fasting hyperglycemia among Filipino women aged 40-79 years in the Philippines, Hawaii, and San Diego.

METHODS

Data were obtained from the (1) Philippine National Nutrition Survey (1998), (2) Native Hawaiian Health Research Project (1997-2001), and (3) University of California San Diego Filipino Women's Health Study (1995-1999). Fasting glucose after an 8h fast, blood pressure, and body mass index (BMI) were measured in all three regions; a 75 g oral glucose tolerance test was performed in San Diego and Hawaii.

RESULTS

The proportion of Filipinas with BMI > or = 30 kg/m2 was higher in Hawaii (20%) compared to women in San Diego (9.3%) or the Philippines (5.2%, p<0.001). Fasting hyperglycemia prevalence (fasting plasma glucose > or = 126 mg/dl or fasting whole blood glucose > or = 110 mg/dl) did not differ among Filipinas in the Philippines (11.8%), San Diego (14.1%), and Hawaii (14.7%, p = 0.323). Type 2 diabetes prevalence was similar among Filipinas in San Diego (31.6%) and Hawaii (24.9%, p = 0.79).

CONCLUSIONS

Despite regional differences in obesity, fasting hyperglycemia was similar among Filipinas in the Philippines, San Diego, and Hawaii and type 2 diabetes prevalence was similar among Filipinas in San Diego and Hawaii.

Genetic basis of type 2 diabetes mellitus: implications for therapy

Type 2 diabetes mellitus represents a multifactorial, heterogeneous group of disorders, which result from defects in insulin secretion, insulin action, or both. The prevalence of type 2 diabetes has increased dramatically worldwide over the past several decades, a trend that has been heavily influenced by the relatively recent changes in diet and physical activity levels. There is also strong evidence supporting a genetic component to type 2 diabetes susceptibility and several genes underlying monogenic forms of diabetes have already been identified. However, common type 2 diabetes is likely to result from the contribution of many genes interacting with different environmental factors to produce wide variation in the clinical course of the disease. Not surprisingly, the etiologic complexity underlying type 2 diabetes has made identification of the contributing genes difficult. Current therapies in the management of type 2 diabetes include lifestyle intervention through diet modification and exercise, and oral or injected hypoglycemic agents; however, not all individuals with type 2 diabetes respond in the same way to these treatments. Because of variability in the clinical course of the disease and in the responsiveness to pharmacologic therapies, identification and characterization of the genetic variants underlying type 2 diabetes susceptibility will be important in the development of individualized treatment. Findings from linkage analyses, candidate gene studies, and animal models will be valuable in the identification of novel pathways involved in the regulation of glucose homeostasis, and will augment our understanding of the gene-gene and gene-environment interactions, which impact on type 2 diabetes etiology and pathogenesis. In addition, identification of genetic variants that determine differences in antidiabetic drug responsiveness will be useful in assessing a first-line pharmacologic therapy for diabetic patients.

Mapping by admixture linkage disequilibrium: advances, limitations and guidelines

Mapping by admixture linkage disequilibrium (MALD) is a theoretically powerful, although unproven, approach to mapping genetic variants that are involved in human disease. MALD takes advantage of long-range haplotypes that are generated by gene flow among recently admixed ethnic groups, such as African-Americans and Latinos. Under ideal circumstances, MALD will have more power to detect some genetic variants than other types of genome-wide association study that are carried out among more ethnically homogeneous populations. It will also require 200-500 times fewer markers, providing a significant economic advantage. The MALD approach is now being applied, with results expected in the near future.

Prevalence and risk factors for prolonged QTc in a multiethnic cohort in rural Hawaii

BACKGROUND

Few studies have examined the biochemical risk factors for prolonged QTc, a predictor of mortality in numerous studies. We report on the prevalence and risk factors for prolonged QTc in a multiethnic population in rural Hawaii.

METHODS

Electrocardiograms were collected from 1415 participants in a cross-sectional survey. The QT interval lengths were corrected for heart rate using Bazett's formula. Linear and logistic regression models were used to examine associations between various cardiovascular risk factors with QTc.

RESULTS

Among the CVD risk factors examined, only age, gender, 2-h glucose, and systolic blood pressure (SBP) were independently associated with QTc interval length. Significant ethnic differences in prevalence were also observed, which persisted after controlling for other risk factors.

CONCLUSIONS

Significant associations between prolonged QTc and ethnic ancestry, but not cholesterol or triglyceride levels, suggest that genetic factors may play a more important role in determining QTc interval length than conventional biochemical and metabolic CVD risk factors.