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Understanding cardiovascular disease (CVD) risk factors among Chinese American children would allow us to target individuals in this group who are at the greatest risk for developing CVD early in life. The purpose of this study is to examine cardiovascular risk factors (increased blood pressure [BP], total cholesterol, low-density lipoproteins, triglycerides, decreased high-density lipoproteins, and increased body mass index [BMI]) in Chinese American children.
A cross-sectional design was used. A total number of 65 children, aged 8 to 10 years, and their mothers participated in the study. Measurements of the children’s weight, height, BP, blood sample, level of physical fitness, activity level, and dietary intake were collected. Mothers completed questionnaires regarding family history of CVD and level of acculturation.
A low level of physical activity and high paternal BMI were associated with higher systolic BP in the children. A low level of physical activity was also found to be a risk factor for higher LDL and systolic BP in the children. A high birth weight and lower parental acculturation level were risk factors for higher BMI in the children.
The findings suggest that a low level of physical activity and high BMI are associated with increased risk of CVD in Chinese American children. The development of culturally appropriate programs that promote an active lifestyle and reduce weight is critical in CVD prevention in Chinese American populations.
In 1998, the World Health Organization designated obesity as a global epidemic that affects all ethnic groups (Fitzgibbon & Stolley, 2004). Chinese Americans are the largest and fastest-growing Asian subgroup in the United States, increasing by 48% between 1990 and 2000. Asian and Pacific Islanders constitute about 4% of the U.S. population; this number is projected to increase to 8% by the year 2050 (Ingram et al, 2003). Recent data indicate, however, that the prevalence of overweight children among Chinese American aged 6 to 11 years is 31% (Tarantino, 2002). In California, about 33% to 39% of Asian and Asian American children (grades 5 to 9) have poor aerobic capacity, and only 29% to 37% of Asian and Asian American children achieved passing scores in all areas of health fitness standards (California Department of Education, 2002). The dramatic increase in the prevalence of overweight children, especially in Chinese American children, indicates that this is an epidemiologic problem requiring immediate attention.
Several physical and psychosocial health consequences are associated with childhood obesity and poor physical fitness, including cardiovascular disease (CVD), sleep disorders, type II diabetes mellitus, and mental health problems such as low self-esteem and social withdrawal (Lawlor & Leon, 2005; Lawlor et al, 2006). Early CVD signs include elevated levels of blood pressure (BP), cholesterol, low-density lipoproteins (LDLs), triglycerides, and body mass index (BMI) and low levels of high-density lipoproteins (HDLs). Increased risk for CVD can result in premature mortality. The adverse effects of CVD signs in childhood persist over time and progress to adult premature CVD (Goran, Ball, & Cruz, 2003). Therefore, it is imperative to identify factors associated with increased risk for CVD in childhood.
The emergence of early CVD in children has been attributed to changes in lifestyle behaviors, including an increase in dietary intake and a decrease in physical activity and fitness (Epstein et al., 2001). Nevertheless, the relationship between obesity and CVD risk appears to vary by ethnicity (Freedam, Bowman, Otvos, Srinivasan, & Berenson, 2002; Glaser & Jones, 1998). The difference could contribute to different concentration of lipids and the activity of lipoprotein lipase among various races. African American children have higher lipids level as well as a higher degree of lipoprotein lipase compared with White children (Freedam et al). Determining which CVD risk factors are especially prevalent among Chinese American children would allow us to target individuals in this group who are at the greatest risk for developing CVD early in life.
Studies have documented that both genetic and environmental factors contribute to the risk of CVD in both children and adults (Agras & Mascola, 2005; Chen, Kennedy, Yeh, & Kools, 2005). For instance, parental weight has been found to be related to children’s weight (Danielzik, Czerwinski-Mast, Langnase, Dilba, & Muller, 2004; Vandewater & Huang, 2006). The role of acculturation is controversial. For example, a lower level of acculturation has been documented to relate to the increasing risk of obesity and CVD (Gadd, Sundquist, Johansson, & Wandell, 2005). However, other studies found that a high level of acculturation is associated with increased risk for obesity and CVD (Gordon-Larsen, Harris, Ward, & Popkin, 2003; McDonald & Kennedy, 2005). The studies by Gorden-Larsen et al. and McDonald and Kennedy measured acculturation based on birthplace of the study participants. While birthplace can be a proxy measure of acculturation, acculturation is a complex concept that includes several dimensions in a person’s experience, including language preference, food preference, and self-defined acculturation level. We explored family factors, including acculturation level, parental weight, and family history of CVD, and children’s factors, including physical activity, physical fitness, and food intake in Chinese American families in San Francisco.
Understanding factors related to the increasing risk of CVD in Chinese American children will be foundational to the development of culturally appropriate and age-specific interventions directed toward improving the physical and psychosocial well-being of Chinese American children.
A cross-sectional study was conducted to explore factors associated with an increased CVD risk (increased BP, cholesterol, LDLs, and triglycerides and decreased HDLs) and BMI in Chinese American children. The children in the study performed a simple physical fitness test and completed standardized questionnaires related to their activity level and dietary intake. The mothers completed questionnaires regarding their family history of CVD and level of acculturation.
Upon approval from the University of California–San Francisco Committee on Human Research, 8- to 10-year-old self-identified Chinese children and their mothers were invited to participate in this study. Participants were recruited from Chinese community sources and after-school programs in the San Francisco Bay area. The research assistants described the study to potential students and gave them an introduction letter and research consent form to take home to their parents. Parents who were interested in the study signed and returned the consent form, providing their names and contact information to the research team. Children provided verbal assent to participant the study. Children and parents also were informed that they could refuse participation or withdraw at any time. Data were collected between November 2004 and July 2005.
Sixty-five children and their mothers participated in this study. Mothers were asked to provide information about the child’s father. Nearly half (49% [n = 32]) of the children were boys. Thirty-five children agreed to provide blood samples for analysis. The mean age of the child was 8.8 years (SD = .5). The mean ages of mother and father were 38.9 years (SD = 6.9) and 43.7 years (SD = 6.3) respectively, and mean years of education were 13.7 (SD = 5.1) and 15.2 (SD = 5.5), respectively.
The procedure for this study entailed administering questionnaires and taking several physiological measurements. The children and their mothers completed all questionnaires at home and returned them in sealed envelopes within 2 weeks of recruitment into the study. Questionnaires for mothers were translated into Chinese and demonstrated adequate validity and reliability. Children completed questionnaires in English.
The Family Information 12-item parent questionnaire includes parent(s)’ and children’s ages, parents’ weight and height, parents’ occupation(s), family income, and parents’ levels of education. Parents also were asked if a physician had diagnosed them, their siblings, their mothers, or their fathers with hypertension, stroke, hyperlipidemia, atherosclerosis, or diabetes. The questionnaire was written at a third-grade reading level and took approximately 5 minutes to complete. Parental BMIs were calculated based on self-report weight and height.
The Suinn-Lew Asian Self-Identity Acculturation Scale (SL-ASIA) was used to examine levels of acculturation (Suinn, 1998). The SL-ASIA scale is a 21-item multiple-choice questionnaire covering topics such as language (four items), identity (four items), friendships (four items), behaviors (five items), general and geographic background (three items), and attitudes (one item). Scores can range from a low of 1.00, indicative of low acculturation or strong Asian identity, to a high of 5.00, indicative of high acculturation or strong Western identity. The scale also permits classification as “bicultural,” indicating that a person has adopted some Asian values, beliefs, and attitudes along with some Western values, beliefs, and attitudes. Validity (factor analysis) and a moderate to good reliability (.79–.91) also have been reported for Chinese Americans (Suinn).
After obtaining parental consent and the children’s assent, the research assistants measured each child’s body weight and height; the children wore lightweight clothes and no shoes. The Seca 214 Road Rod (Vogel & Halke GmbH & Co., Hamburg) portable stadiometer, which has an excellent graduation of 1/8 in (0.1 cm), was used to measure height. Children were instructed to have their head positioned in the Frankfort Plane and to inhale; stretch height was then measured. Body weight was measured using the 840 Bella Digital Scale (Vogel & Halke GmbH & Co., Hamburg), which has a graduation of 0.2 lb (100 g). Scales were calibrated based on the instructions provided by the companies before each subject was measured. BMI was calculated by dividing body mass in kilograms by height in meters squared (kg/m2). BMI has acceptable ranges of sensitivities and specificity. Sensitivity ranged from 29% to 88%, specificity ranged from 94% to 100%, predictive value ranged from 90% to 100%, and efficiency ranged from 85% to 100% in children (de Onis, 2004).
In this study, body weight and height were measured three times and the mean values of the three measurements were used to determine BMI. BMI lower than the 5th percentile was defined as underweight, between the 6th and 84th percentile was defined as normal weight, and above the 85th percentile was defined as at risk for overweight and overweight, based on the growth chart developed by Centers for Disease Control and Prevention (CDC) (CDC, 2000).
After a 15-hour period of fasting, a research assistant collected a blood sample to measure levels of cholesterol, HDL, LDL, triglycerides, and glucose. The sample consisted of approximately three drops of blood drawn from the fingertips of the child by using appropriate blood sampling lancets. These tests require 10–15 µL of blood (three drops) from the fingertips. The Polymer Technology Systems-Bio-Scanner 2000 was used to measure HDL, triglycerides, cholesterol, and glucose levels. The scales were calibrated based on the instructions provided by the companies. These blood tests were used as indicators of CVD risk.
Muscular endurance was measured by a sit-up test, with the number of sit-ups performed in a period of 1 minute being recorded. The children were instructed to lie down on a mat with their knees bent at a right angle, feet on the floor, and their hands behind their heads. A partner firmly held their ankles for support and to maintain the count. Flexibility was measured using a sit-and-reach test, which is scored as the most distant point (in cm) reached on the ruler with the fingertips in a sit-and-reach box, a specially constructed box with a measuring scale, where 23 cm is at the level of the feet. We asked the children to take the test while they sat in front of the box. Each subject was given three trials, and the best result was chosen. Validity of these test was between 0.96 and 0.99, and reliability was .98 (Chun, Corbin, & Pangrazi, 2000).
In the Children Self-Administered Physical Activity Checklist (SAPAC) questionnaire, children were asked to recall activities that occurred the previous day. The questionnaire contains 25 questions related to activities and two questions related to sedentary activities. The children in the study estimated the number of minutes they spent in each activity during three periods: before school, during school, and after school. They also were asked to report whether the activity caused them to “breathe hard or feel tired.” The frequency and intensity of activities were scored only if they totaled 5 minutes or more in an intensity category for one point of the time. Total physical activity and sedentary time are computed. Metabolic equivalents, referring to energy expenditure, were computed based on the reported frequency and intensity. The SAPAC provided a moderate validity criterion (r = .57–.75) and a moderate test-retest reliability (r = .60) (Sallis et al., 1996). Children were asked to record all activities during one weekend and two weekday 24-hour periods.
The Kid’s Food Frequency Questionnaire (KFQ) is a quantitative self-report food frequency questionnaire to measure a child’s food consumption by indicating the exact number of times each food was eaten per week (Block, Woods, Potosky, & Clifford, 1990). A picture of the portion size is provided to help participants in determining the portion size. Daily intake of energy and nutrients is estimated by multiplying frequency responses with the specific portion sizes and the nutrient values assigned to each food item. The KFQ has a scannable form, and a computer software program can measure the consumption of calories, percentage of calories from total fat and from saturated fat, sugar, and vegetable intake from all food items. Parents completed the KFQ together with their child. In this study, we examined total calorie intake, percentage of calories from total fat, and vegetable intake in terms of number of serving per day.
Descriptive statistics were calculated initially for demographic characteristics and all major study variables. We performed ttests to examine any difference in the variables between genders and overweight and normal-weight children. Linear regressions were computed to examine correlation between variables and CVD risk factors, and stepwise multivariate linear regression models were used to examine factor(s) contributing to CVD risk and increased BMI in Chinese American children. All analyses were performed in SPSS 13.0 for Windows.
The average BMI was 18 kg/m2 (SD = 3.7) for children, 23.1 kg/m2 (SD = 4.1) for mothers, and 24.8 kg/m2 (SD = 4.2) for fathers. We found that 4.6% of children were underweight (n = 3), as their BMI was below 5th percentile based on CDC growth charts (CDC, 2000); 58.5% of children (n = 38) were normal weight (BMI between 5th and 84th percentile); and 36.9% (n = 24) were overweight (BMI above 85th percentile). Of the overweight children, 62.5% were boys (n = 15) and 37.5% were girls (n = 9). Sample characteristics and data are presented in Table 1. Compared with the most recent National Health and Nutrition Examination Survey (NHANES) data for children (Ogden et al, 2006), our sample demonstrated similar overweight concerns in Chinese American children (see Figure 1).
Overweight and non-overweight children demonstrated similar levels of physical activity, dietary intake, and physiologic measures, including BP, cholesterol, HDL, LDL, and triglycerides. Additionally, parental BMI, parental educational levels, and parental levels of acculturation were similar between overweight and non-overweight children.
Lower levels of parental acculturation were associated with higher BMI in children (R2 = .09, P = .02) and higher cholesterol (R2 = .13, P = .05). A higher maternal BMI also was correlated with higher levels of BMI in children (R2 = .07, P = .05). A higher BMI was related to a higher level of LDL (R2 = .24, P = .03) and higher cholesterol (R2 = .11, P = .05).
Multivariate regression model indicates that a low level of physical activity (sr2 = .19, P = .001) and high paternal BMI (sr2 = .13, P = .005) contributed to higher systolic BP in these children (R2 = .27, F = 8.58, P= .007), whereas a higher vegetable intake in children contributed to higher diastolic BP (R2 = .14, F = 7.89, P = .007).
A low level of physical activity also was found to contribute to higher LDL and systolic BP in these children (R2 = .38, F = 8.64, P = .01; R2 = .27, F = 7.97, P = .007). Being a boy, having a lower parental acculturation level, and having a higher paternal BMI contributed to higher cholesterol levels in the children (R2 = .61, F = 8.68, P = .001). A high birth weight (sr2 = .24, P = .0001) and lower parental acculturation level (sr2 = .05, P = .05) contributed to higher BMI in the children (see Table 2).
When compared with national data collected in 2004, our data indicated a similar overweight prevalence in Chinese American children. Childhood obesity has affected children of all ethnic groups in the United States, as demonstrated in Figure 1. Because Chinese Americans are the fastest-growing Asian population in the United States, it is important for health care providers and researchers to investigate risk factors for being overweight in this group to prevent health issues related to being overweight in children.
Results suggest that overweight and non-overweight Chinese American children have similar characteristics in terms of dietary behavior, physical activity, and blood measures. However, a higher BMI in the children was found to be related to higher levels of LDL and total cholesterol. Positive relationships between high body composition in children and increased risk for CVD have been suggested in several studies (Freedam et al, 2002; Goran et al, 2003). Lai, Ng, Lin, and Chen (2001) found that obesity was associated with hypertriglyceridemia, a high level of LDL, and a low level of high HDL in Chinese children in Taiwan. The Taipei Children’s Heart Study also found positive associations between obesity and BP, blood glucose, and lipid concentrations among school children in Taiwan (Chu, Wang, & Shieh, 2001). Studies of Chinese children and adults found that being overweight in a child was a significant factor for CVD risk (Li et al., 2005; Zhou et al., 2002). Consistent with the literature, our study found that a higher BMI puts Chinese American children at greater risk for CVD, especially when measured in terms of cholesterol and LDL levels. Thus, strategies to prevent obesity in children are crucial in preventing CVD risk in Chinese American children.
Besides higher BMI, results of our study suggested the negative relationship between physical activity, LDL, and systolic BP in these children. A lower level of physical activity has been suggested to increase the risk for CVD and a higher level BP (Nielsen & Andersen, 2003). This is consistent with a cross-sectional study of 13,557 boys and girls, 15 to 20 years of age, that found that a low physical activity level and high BMI were independently associated with a high BP and risk of having hypertension in both genders (Nielsen & Andersen).
The current study findings support the literature and suggest that the risk for high BP and LDL can be seen in children with low levels of physical activity. Engaging in physical activities on a regular basis has been found to decrease the prevalence of obesity, risk of death from CVD, diabetes, and high cholesterol (Goran et al, 2003; Kollipara & Warren-Boulton, 2004). Studies have found that Asian American children report lower levels of physical activity than do White and African American children, and fewer than 20% of Asian students (in grades 5 through 12) met the Year 2000 goal for strenuous physical activity (Wolf et al., 1993). Because Chinese American children have been found to have a lower level of physical activity compared with their White counterparts, the development of culturally appropriate programs that promote active lifestyle for the child and the whole family is critical for CVD prevention.
In this study, we used SL-ASIA to measure maternal acculturation level. The SL-ASIA has been used to measure acculturation in Chinese-Americans with adequate reliability and validity. The results of the current study, indicating that children from families with low acculturation levels have a higher risk for being overweight and having high levels of cholesterol, are consistent with other studies suggesting that lower acculturation is a risk factor for obesity in children (Olvera, Suminski, & Power, 2005). Acculturation has an impact on one’s beliefs, attitudes, and behaviors. Immigrants’ health status changes are the result of higher levels of acculturation in the second and third generations (Davis & Reid, 1999). Families with low acculturation levels may have inadequate access to health and educational resources regarding healthy nutrition and weight, resulting in a limited awareness of obesity and health issues related to obesity. Because acculturation is an important factor related to CVD risk, interventions must tailored to families with different acculturation levels. For example, if access to health care information is limited to low-acculturated families because they prefer to receive information in the language of their preference, health care providers need to be aware of such needs and provide information based on the language as well as via culturally appropriate methods.
Another important factor related to children’s health is parental BMI. Our study found that higher paternal BMI was associated with higher level of systolic BP and that total cholesterol and higher maternal BMI were related to a higher level of BMI in their children. This finding is consistent with previous studies indicating the impact of parent’s health and health behavior on their children’s health and health behaviors (Danielzik et al., 2004; Sekine et al., 2002). The relationship between parental health and health behavior and their children’s health may be due to both genetics and parental role modeling. For instance, studies also have found that children’s BMI, dietary behaviors, and physical activity levels are influenced by their parents’ BMI and physical activity level and dietary intake (Danielzik et al.; Sekine et al.). Thus, interventions to reduce CVD risk need to include the parents and family.
Our findings attest to the importance of evaluating growth and weight gain in young children. In addition to parental BMI, a higher birth weight was found to increase the risk for being overweight in childhood. Higher birth weight has been documented as a risk factor for being overweight later in childhood (Dennison, Edmunds, Stratton, & Pruzek, 2006). Thus, early childhood may be a particularly important period in which there is an increase in variation in levels of relative weight associated with weight at birth. Health care providers may want to provide education to parents regarding appropriate growth during the fetal stage and early infancy due to possible later adverse health consequences related to nutrition and obesity.
Because this is one of the first studies to examine CVD risk factors among young Chinese American children, there were some limitations. Because this is a cross-sectional study, causal relationships cannot be established. Results can be generalized only to similar populations. In addition, issues related to convenience sampling also exist, because the children and families who participated in this study may be more aware of health issues related to physical activity and obesity and have healthier lifestyles than those who declined to participate. Furthermore, because the study used only self-report measures of children’s food intake, physical activity, sedentary activity, and weight and height of parents, errors in measurement might have occurred. Use of observation techniques and physiologic measures of physical activity (such as heart rate and oxygen consumption) may enhance the reliability and validity of study results. In addition, the sample size is small especially for the blood testing in this study. Future studies would have wider applicability if they included more diverse and larger samples and used longitudinal designs to examine changes in BMI and CVD risk over longer periods of time.
Despite the limitations, the results of this study provide new information on CVD and overweight risk factors in this fast-growing minority population in the United States. Our study found that children with higher birth weights, higher BMI, and low levels of physical activity and who have overweight parents with low acculturation levels are at risk for CVD. Thus, adequate prenatal nutrition and culturally sensitive programs tailored for Chinese American families can help improve health and prevent CVD in children. Development of culturally sensitive and age-appropriate interventions is crucial in preventing and treating childhood obesity.
The data in this study are critical as a basis to understand factors related to the increasing risk of CVD in Chinese American children. This information is essential to the development of culturally appropriate and age-specific interventions directed toward improving the physical and psychosocial well-being of Chinese American children.
A higher BMI in the children was found to be related to higher levels of LDL and total cholesterol.
In addition to parental BMI, a higher birth weight was found to increase the risk for being overweight in childhood.
Development of culturally sensitive and age-appropriate interventions is crucial in preventing and treating childhood obesity.
We would like to acknowledge children and families involved in the study and Drs. Robert Lustig, Melvin B Heyman and Sandra Weiss for their assistant in the review of the manuscript.
This study was supported by a University of California-San Francisco School of Nursing research grant and NIH roadmap (K12 HD049077).
Jyu-Lin Chen, Department of Family Health Care Nursing, University of California–San Francisco.
Yuaner Wu, Department of Physiological Nursing, University of California–San Francisco.