Cardiovascular risk in Japanese-Brazilian subjects

Risco cardiovascular em nipobrasileiros

Abstracts

OBJECTIVE: To evaluate the prevalence of risk factors for cardiovascular disease in Japanese-Brazilian subjects. SUBJECTS AND METHODS: One hundred thirty-one residents of the Mombuca community were studied. Statistical analysis was based on the X² test, Fisher's Exact test, Student's t test, and ANOVA, at a 5% significance level. RESULTS: The average age was 56.7 years-old; 76.3% had dyslipidemia, 24.4% pre-diabetes (PDM), 10.7% type 2 diabetes mellitus (T2DM), 46.6% hypertension, 52.7% abdominal obesity, and 35.8% metabolic syndrome (MS). There were significant correlations between HOMA-IR and MS diagnosis and obesity, while HOMA-β levels were decreased in T2DM and PDM. The ankle-brachial index was positive for peripheral artery disease in 22.3% of the individuals. Electrocardiograms did not show increased evidence of myocardial ischemia. CONCLUSION: Subjects of this community are exposed to major cardiovascular risk factors, namely high prevalence of MS diagnoses and increased HOMA-IR. Arq Bras Endocrinol Metab. 2012;56(9):608-13

Metabolic syndrome; ankle-brachial index; HOMA; cardiovascular risk; Japanese-Brazilian subjects; Mombuca

ORIGINAL ARTICLE

Cardiovascular risk in Japanese-Brazilian subjects

Risco cardiovascular em nipobrasileiros

Patricia Moreira Gomes^I; Regina Célia Garcia de Andrade^II; Roberta Carvalho de Figueiredo^III; Ana Emília Pace^IV; Amaury Lelis Dal Fabbro^III; Laércio Joel Franco^III; Milton César Foss^I; Maria Cristina Foss-Freitas^I

^IDepartment of Internal Medicine, School of Medicine of Ribeirao Preto, Universidade de Sao Paulo (FMRP-USP), Ribeirao Preto, SP, Brazil

^IIRibeirao Preto Pharmacy School, USP, Ribeirao Preto, SP, Brazil

^IIIDepartment of Social Medicine, FMRP-USP, Ribeirao Preto, SP, Brazil

^IVRibeirao Preto Nursing School, Ribeirao Preto, SP, Brazil

^{Correspondence}

ABSTRACT

OBJECTIVE: To evaluate the prevalence of risk factors for cardiovascular disease in Japanese-Brazilian subjects.

SUBJECTS AND METHODS: One hundred thirty-one residents of the Mombuca community were studied. Statistical analysis was based on the X² test, Fisher's Exact test, Student's t test, and ANOVA, at a 5% significance level.

RESULTS: The average age was 56.7 years-old; 76.3% had dyslipidemia, 24.4% pre-diabetes (PDM), 10.7% type 2 diabetes mellitus (T2DM), 46.6% hypertension, 52.7% abdominal obesity, and 35.8% metabolic syndrome (MS). There were significant correlations between HOMA-IR and MS diagnosis and obesity, while HOMA-β levels were decreased in T2DM and PDM. The ankle-brachial index was positive for peripheral artery disease in 22.3% of the individuals. Electrocardiograms did not show increased evidence of myocardial ischemia.

CONCLUSION: Subjects of this community are exposed to major cardiovascular risk factors, namely high prevalence of MS diagnoses and increased HOMA-IR. Arq Bras Endocrinol Metab. 2012;56(9):608-13

Keywords: Metabolic syndrome; ankle-brachial index; HOMA; cardiovascular risk; Japanese-Brazilian subjects; Mombuca

RESUMO

OBJETIVO: Avaliar a presença de fatores de risco para doença cardiovascular em nipo-brasileiros.

SUJEITOS E MÉTODOS: Foram estudados 131 moradores de Mombuca. Utilizaram-se os testes do Qui-quadrado, Exato de Fisher, t de Student e ANOVA, com significância de 5%.

RESULTADOS: A média de idade foi de 56,7 anos; 76,3% tinham dislipidemia, 24,4% pré-diabetes (PDM), 10,7% diabetes melito tipo 2 (DM2), 46,6% hipertensão, 52,7% obesidade abdominal e 35,8% síndrome metabólica (SM). Houve correlação significativa do HOMA-IR com SM e obesidade, enquanto HOMA-β esteve reduzido na presença de DM2 e PDM. O índice tornozelo-braquial foi positivo para doença arterial periférica em 22,3% dos indivíduos. O eletrocardiograma não mostrou aumento de isquemia miocárdica.

CONCLUSÃO: A comunidade está exposta aos fatores de risco maiores para doença cardiovascular, o que pode ser resumido pela alta prevalência de diagnóstico de SM e valores elevados de HOMA-IR. Arq Bras Endocrinol Metab. 2012;56(9):608-13

Descritores: Síndrome metabólica; índice tornozelo-braquial; HOMA; risco cardiovascular; nipo-brasileiros; Mombuca

INTRODUCTION

There is considerable evidence that type 2 diabetes mellitus (T2DM) has become an important public health problem in Japanese-Brazilian subjects (1,2). The mortality rate for T2DM in Sao Paulo is twice as high among first-generation immigrants as that observed in Japan (1). Japanese people exposed to Wes­tern culture now are more affected by cardiovascular disease (CVD), and the disease is strongly associated with changes in the diet and level of physical activity (3).

In addition to T2DM, hypertension (HT), dyslipidemia, and obesity are well-established risk factors for CVD. The combination of these four diseases is known as metabolic syndrome (MS), a disorder related with insulin resistance and central fat deposition. MS diagnosis has become increasingly important because of its strong association with greater cardiovascular risk.

The leading cause of peripheral arterial disease (PAD) is atherosclerosis. In the Framingham study, it was observed that the prevalence of PAD increases with age and with risk factors for CVD (4). Atherosclerotic dise­ase of at least one coronary artery is identified in about 60 to 80% of patients with PAD of the lower limbs. The ankle brachial index (ABI) is able to diagnose PAD at all stages of the disease, except for individuals with non-compressible arteries, making the index an interesting and simple tool to identify individuals at risk for CVD.

In the Mombuca community, Guatapara, located in the state of Sao Paulo, Brazil, there is a population that migrated from Japan in 1962, living as a semi-rural community that has retained much of their traditional habits. This adult population is mostly composed by Isseis (people born in Japan and who migrated to Brazil) and, in smaller proportions, by Niseis (children of Isseis). Thus, considering the recent migration and maintenance of the Japanese tradition in a considerable degree, we aimed at determining the prevalence of CVD risk factors in the Japanese-Brazilian population of Mombuca/Guatapara.

SUBJECTS AND METHODS

The study was conducted in the community of Mombuca/Guatapara from April to December 2005, and included 131 individuals (69.2% Isseis and 30.8% Niseis), representing 66.8% of the adult population living in the community. In this group of patients, 54 (41.2%) were men and 77 were (58.8%) women, with a mean age of 57 ± 16 years. Clinical and laboratory evaluations were performed by trained professionals with adequate equipment. The Ethics Committee of the University Hospital of the School of Medicine of Ribeirao Preto-USP approved the study protocol, and all participants signed a written informed consent form to participate in the study.

Clinical history data was obtained by a standardized questionnaire. All participants were asked about their current and former health problems, and the diseases were classified using the International Classification of Diseases (ICD-10). Anthropometric evaluation was performed with the participants wearing light clothes and no shoes. The weight in kilograms was assessed in an electronic scale (Filizola^®), and height, in centimeters, was measured with a portable stadiometer. Body mass index (BMI) was calculated by dividing weight (kg) by height (m) squared. Patients were categorized according to BMI values ​​determined by the International Obesity Task Force (IOTF) for the Asian population: between 23 and 24.9 kg/m² for overweight, and ≥ 25 kg/m² for obesity (5).

Waist circumference was measured midway between the lower edge of the last rib and the iliac crest, and used to determine the abdominal obesity (AO). An automated device (OMRON^®, Itapevi, Brazil) with the appropriate cuff was used to assess blood pressure (BP). Normal values were those recommended by the VI Brazilian Guidelines for Hypertension (2010) (6).

A fasting blood sample was obtained, and concentrations of triglycerides, HDL cholesterol, basal insulin, and glucose were assessed using automated techniques. For measures of triglycerides (TG), total cholesterol (TC), and HDL-cholesterol (HDL-C) we used an automated spectrophotometric method (Wiener lab, Rosario, Argentina). Values ​​of LDL-cholesterol (LDL-C) were calculated using the Friedewald formula, except when TG values ​​were ≥ 400 mg/dL. Glucose was measured by an ​​enzymatic method (hexokinase), and the diagnosis of DM was made ​​according to the criteria of the World Health Organization (WHO), 1999. Impaired fasting glucose (IFG) and impaired glucose tole­rance (IGT) were grouped as pre-diabetes (PDM) (7).

Basal insulin was measured by radioimmunoassay (Coat-a-Count insulin, Siemens Healthcare Diagnostics, Los Angeles, CA USA). The HOMA-beta was calculated by the formula: [20xBasal Insulin (µU/mL)] / [fasting glucose (mmol/L) - 3.5], with reference values ​​from 167 to 175, and the HOMA-IR by the formula: [fasting glucose (mmol/L) x Basal Insulin (µU/mL)] / [22.5], with normal values ​​below 2.71 (8).

MS was evaluated by the criteria of International Diabetes Federation (IDF)/2009, which proposes different values ​​of CA according to the ethnicity of the individual. In this study, we used the CA values ​​determined for the Japanese population, in which values ​​of ≥ 90 cm for men and ≥ 80 cm for women are considered high (9).

Participants were submitted to electrocardiogram (ECG) at rest, using a portable HEARTWARE ECG98 Panel v2.0.1.1, and ankle-brachial index (ABI) was measured using a portable 8-MHz Doppler and pressure cuffs of appropriate size positioned at arm and calf. To calculate ABI, we divided the highest values ​​of systolic blood pressure of each leg (posterior tibial artery or dorsalis pedis artery) by each lower limb (brachial artery). Peripheral artery disease (PAD) was diagnosed when ABI was less than 0.9 in any hemibody.

For statistical analysis, data were expressed as means and standard deviations for continuous variables, and absolute numbers and percentages for categorical variables. Continuous variables were compared by Student's t-test or ANOVA, and categorical variables by χ² test or Fisher's Exact test. HOMA indices were compared with the following variables, using Fisher's exact test: blood glucose (normal, pre-diabetes, and diabetes mellitus), presence of DM, MS, overweight, and obesity. The level of significance was 0.05. Data were analyzed using the SAS^® 9.1 software.

RESULTS

Of the 131 (66.8%) individuals included in the study, only seven individuals had a diagnosis of angina/myocardial infarction or stroke.

The average age of the population showed no significant difference between genders, being 57.8 years for females and 55.2 years for males (Table 1). Ho­wever, women presented significantly higher levels ​​of LDL-C (p = 0.03) and HDL-C (p = 0.02), and a greater number of individuals who never smoked (p = 0.001), while men had higher systolic BP (p = 0.028) and diastolic BP (p = 0.006), and more smokers (p < 0.001) or former smokers (p = 0.001). There was no difference between genders regarding any other parameter evaluated (Table 1).

The prevalence of overweight and obesity were respectively 29.6% and 46.3% among men, and 15.6% and 39% among women. Abdominal obesity, evaluated by the abdominal circumference, was significantly more frequent among men (Table 2).

A total of 100 (76.3%) ECG examinations were analyzed by a cardiologist and the findings were divided into two categories: 1) nonspecific (n = 74): reports that were described as normal, disorders of ventricular re-polarization, low amplitude QRS interval and changes in conduction inferior parietal were grouped in this cate­gory; 2) specific changes (n = 26): blockade, ischemia and arrhythmia. The groups were similar (p > 0.05) for any of the variables studied (Table 3). ABI was positive for PAD in 22.3% of the 131 patients evaluated; however, there was no correlation with ECG alterations.

We observed significant lower values for HOMA-β in T2DM (p = 0.03), and increased HOMA-IR in obese patients (p = 0.01) and in patients with MS diagnosis (p = 0.02). When data was analyzed according to gender, we observed increased HOMA-IR values in women with MS diagnosis (p = 0.004), while men had lower HOMA-β in patients with higher blood glucose (p = 0.003) or T2DM diagnosis (p = 0.002). We also found increased HOMA-IR in overweight men (p = 0.01) (data not shown). When HOMA values were analyzed in normal glucose (N), PDM and T2DM individuals, we did not observe significant differences in the values of the HOMA-IR among the groups, but we did find lower values of HOMA-β in the PDM and T2DM groups (Table 4).

DISCUSSION

In this study, the majority of the population (68.7%) consisted of adult individuals born in Japan (Issei), characterizing a community that was formed recently. Women made up most of the group, which can be attributed to the fact that men move out of the community to work or study, and even the recent wave of immigration back to Japan.

Obesity is not commonly observed among Japanese migrants in the Americas (10), but the absence of a high BMI does not exclude the occurrence of increased visceral fat deposition. Visceral obesity causes a reduction in glucose utilization mediated by insulin, and is clearly related with insulin resistance.

According to the National Nutrition Survey in Japan (2004), the prevalence of obesity (BMI > 25 kg/m²) in Japanese men and women is 30% and 28%, respectively (11). These values ​​are lower than those shown in this study, in which the prevalence of overweight and obesity were respectively 29.6% and 46.3% among men, and 15.6% and 39% among women. Our data are similar to those reported in the Japanese-Brazilian subjects from Bauru, Sao Paulo/Brazil, where the prevalence of overweight (BMI > 25 kg/m²) was 40.2% (12).

Similarly, our population showed mean abdominal circumference values close to those found in the Japanese-Brazilian subjects in Bauru (12), but inferior to Asian-American men in Seattle, United States (10). Anyhow, the average values ​​of the abdominal circumference in the population of Mombuca were higher than those of Japanese living in Japan, both men and women (13).

Moreover, AO was significantly more frequent among men than women. Our results differ from the data on Japanese-Brazilian subjects from Bauru (1). Additionally, in Bauru, the prevalence of AO was greater than the overall prevalence of obesity, while in Mombuca we observed the opposite. In this study, the prevalence of overall obesity (41.9%) was greater than the prevalence of AO (35.7%), supporting other studies that suggest combined analysis of BMI and fat distribution increases the predictive power for CVD and metabolic disorders (14).

Mild or moderate elevations of serum triglycerides and lower serum levels of HDL cholesterol are observed in overweight and obese individuals. However, serum levels of LDL cholesterol may or may not be increased (15). In Mombuca, averages for total cholesterol or fractions and triglycerides were within the normal range.

Several studies have shown that residents of Japanese descent outside of Japan are more susceptible to T2DM, dyslipidemia, ischemic heart diseases, and cerebrovascular diseases (12,16,17). The term metabolic syndrome is accepted by the international medical community as a tool capable of identifying individuals with multiple risk factors for CVD and diabetes mellitus (18). We observed a prevalence of 10.7% of T2DM, 46.6% of hypertension, and 35.8% of metabolic syndrome, showing that there is a significant portion of indivi­duals exposed to well-established cardiovascular disease risk factors. The highest incidence of these diseases can occur due to greater genetic susceptibility which, along with changes in lifestyle, lead to deterioration of glucose metabolism, lipids, increased blood pressure, and obesity (1,19,20).

Epidemiological studies that used ECG showed the importance of left ventricular hypertrophy and abnormal Q waves to predict CVD (21-23). In fact, in the Japanese community of Bauru, Q waves, representing myocardial necrosis, were frequent in the ECGs. Our data showed no specific differences in age, fasting blood glucose, lipids, changes in blood pressure and BMI according ECGs findings. This could be explained by the fact that the population is still made ​​up of adults with an average age of less than 60 years, and that the population still retains many of the habits brought from Japan, as well as their work in agriculture. Also, ECG is not very sensitive to predict and diagnose cardiovascular disease.

We did not observe any correlation between ECGs findings and ABI results, either, what may suggest that ABI was not an adequate tool to evaluate atherosclerosis in this population. Perhaps this correlation was not possible because of the small number of individuals studied, and because the evaluation of ABI was not performed by the same researcher. However, it is known that the prevalence of PAD depends on the age of the population studied and the presence of other risk factors or other atherosclerotic events, such as coronary artery disease or cerebrovascular disease. Anyhow, in accordance with other studies, we found a correlation between HOMA-IR and MS (24), reflecting high risk for atherosclerotic disease in this population. We also found that HOMA-β decreases progressively depending on the evolution of glucose abnormalities.

Thus, we conclude that the Japanese-Brazilian subjects from Mombuca/Guatapara are exposed to major cardiovascular risk factors, namely high prevalence of MS diagnoses and increased HOMA-IR values. Although ECG and ABI were not able to identify individuals at risk for CVD at the time of the study, these tools should still be used. Further studies are necessary to evaluate the use of more sensitive techniques to assess cardiovascular disease in this population.

Acknowledgements: we are grateful to patients participating in this study and to Sebastiao L. Brandao Filho for technical assistance. This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Disclosure: no potential conflict of interest relevant to this article was reported.

Received on Feb/6/2012

Accepted on Aug/23/2012

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Publication Dates

• Publication in this collection
  15 Jan 2013
• Date of issue
  Dec 2012

History

• Received
  02 June 2012
• Accepted
  23 Aug 2012