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Print version ISSN 0021-7557
J. Pediatr. (Rio J.) vol.80 no.2 Porto Alegre Mar./Apr. 2004
Ceres C. RomaldiniI; Hugo IsslerII; Ary L. CardosoIII; Jayme DiamentIV; Neusa FortiV
School of Medicine, Universidade de São Paulo (USP). Assistant physician,
Division of Nutrition and Metabolism, Instituto da Criança, Hospital
das Clínicas, School of Medicine, Universidade de São Paulo (USP),
São Paulo, SP, Brazil
IIPhD. Professor, Department of Pediatrics, School of Medicine, Universidade de São Paulo (USP), São Paulo, SP, Brazil
IIIPhD, School of Medicine, Universidade de São Paulo (USP). Chief of the Division of Nutrology, Instituto da Criança, Hospital das Clínicas, School of Medicine, Universidade de São Paulo (USP), São Paulo, SP, Brazil
IVProfessor, School of Medicine, Universidade de São Paulo (USP). Instituto do Coração, Hospital das Clínicas, School of Medicine, Universidade de São Paulo (USP), São Paulo, SP, Brazil
VPhD. Assistant professor, School of Medicine, Universidade de São Paulo (USP), São Paulo, SP, Brazil
To identify the prevalence of dyslipidemia in a group of 109 children and adolescents
with a family history of premature coronary artery disease and to investigate
the association between dyslipidemia and other risk factors for atherosclerosis.
METHODS: Total cholesterol, low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), triglycerides, body mass index, blood pressure, physical activity, smoking, per capita income and maternal schooling were investigated.
RESULTS: Total cholesterol and LDL-C levels were higher than desirable in 27.5% and 19.3%, respectively, of our patients; 13.8% had lower HDL-C values and 13.0% presented hypertriglyceridemia. Obesity and excess weight were observed in 25.7% of the cases. Out of these, 57.1% had abnormal lipid values. Dyslipidemia was observed in 38.5%, either alone or in combination with other risk factors. Smoking was observed in 3.6%, hypertension in 2.7% and physical inactivity in 72.5%. There was no relationship between dyslipidemia and per capita income, maternal schooling and physical inactivity. However, obesity and excess weight were identified as significantly associated with the occurrence of dyslipidemia (p = 0.02; odds ratio = 2.82, 95% CI = 1.6-6.81).
CONCLUSION: In children and adolescents with a family history of premature coronary artery disease, early identification of the risk factors for atherosclerosis is essential to allow the implementation of preventive measures.
Hypercholesterolemia, dyslipidemia, coronary artery disease, atherosclerosis, lipoproteins.
Coronary artery disease (CAD), secondary to atherosclerosis stands out as the primary cause of morbidity and mortality in modern industrialized societies. In the United States it was responsible for a third of all deaths in 1998.1 Brazilian data reveals that the situation in our country is similar. In the same year, 32.6% of deaths from known causes were the result of diseases of the circulation.2
Clinical manifestations of coronary artery disease, such as myocardial infarction, stroke and peripheral vascular disease generally have onset from middle age onwards. However, studies indicate that the atherosclerotic process begins to develop during childhood. Fatty streaks, precursors to atherosclerotic plaques, begin to appear on the tunica intima of the aorta at three years of age3 and on the coronary arteries during adolescence, progressing significantly during the thirties and forties.4 Development of symptomatic CAD has been correlated with atherosclerosis risk factors. Among the most important of these factors are a family history of CAD, dyslipidemia, arterial hypertension, diabetes mellitus, obesity, smoking and a sedentary lifestyle.5,6
Research has documented the association between a family history of CAD and the presence of atherosclerosis risk factors in children and adolescents.7-9 It is believed that the occurrence of CAD in ancestors younger than 55 or 65 for men and women respectively, termed premature CAD, confers a significant risk for the disease.10,11
Dyslipidemia is a condition in which there are abnormal lipid or lipoprotein concentrations in the blood and is a risk factor for the development of atherosclerosis complications. The correlations between elevated serum total cholesterol (TC) levels, particularly low density lipoproteins (LDL-C) and CAD have been well documented for foreign populations, as has the association between reduced high density lipoprotein concentrations and CAD.12,13 Many different studies have related childhood cholesterol concentrations with those found in adultyhood.14,15
In our country there have been few studies16-18 discussing the association between dyslipidemia prevalence and other atherosclerosis risk factors in children and adolescents with family histories of premature CAD. This being the case we performed assays of the serum concentrations of TC, LDL-C, HDL-C and triglycerides (TG) from a sample of children and adolescents with family histories of CAD manifesting before 55 for men and 65 for women and evaluated their relationship with CAD risk factors.
Patients and methods
During the period between March 1998 and February 2000 109 children and adolescents were studied. They were all registered at the of the Instituto da Criança Nutrition and Metabolism Unit at the Hospital das Clínicas (HC) of the Medical Faculty of the Universidade de São Paulo (FMUSP) and had been referred from the Instituto do Coração at the HC of the FMUSP as belonging to a high-risk group for atherosclerosis, having ancestors who had contracted premature CAD.
Children and adolescents, resident in the city of São Paulo, older than two years and younger than twenty and whose parents or grandparents had undergone myocardial revascularization surgery, at ages below 55 for men and 65 for women, at the Instituto do Coração of the HC at the FMUSP were included in the study.
Exclusion criteria were diabetes mellitus, hypothyroidism, nephrotic syndrome, chronic renal failure, chronic cholestatic liver diseases or use of corticosteroids, beta-blockers, anabolic steroids or contraceptives.11
This was a cross-sectional study evaluating socio-economic variables (number of years the mother spent at school and family income), physical activity, smoking, weight, height and arterial blood pressure.
Each child or adolescent's body mass index (BMI), expressed in kg/m2, was calculated. Using the National Center for Health Statistics (NCHS)19 BMI for age and sex curves as reference values, we investigated obesity (BMI equal to or greater than the 95th percentile), overweight (BMI equal to or greater than the 85th percentile but less than the 95th), normal weight (BMI greater than or equal to the 5th percentile and below the 85th percentile) and underweight (BMI less than the 5th percentile). We defined both overweight and obesity as excessive weight.
Systolic and diastolic pressures were considered normal when below the 95th percentile, in accordance with the Report of the Second Task Force on Blood Pressure Control in Children (1987).20
Venous blood samples were collected after a minimum of 12 hours fasting for serum concentrations of TC, LDL-C, HDL-C and TG to be tested. Assays were performed at the Central Laboratory Central of the HC at the FMUSP following routine procedures. Reference values were taken from the National Cholesterol Education Program10 recommendations as referred to be the Third Brazilian Directives on Dyslipidemia11 (Table 1). In cases of abnormal results tests were repeated and an average taken of the two results.
Depending on laboratory results, dyslipidemia was classified as: 1) isolated hypercholesterolemia (elevated TC only, generally due to increased LDL-C); 2) isolated hypertriglyceridemia (elevated TG values only); 3) mixed hyperlipidemia (elevated TC and TG values); 4) reduced HDL-C in isolation or in association with increased LDL-C and/or TG.11
The physical activity variable was divided into the following categories: daily physical activity, twice or thrice a week, occasionally and no physical activity whatsoever. Adolescents that reported smoking at least five cigarettes per day were classed as smokers.16 Family income was measured in multiples of the national minimum salary per capita per month. Maternal education was split into two categories: those who had not passed the seventh grade and those who had completed from the eighth grade onwards.
Either Fisher's exact test or the chi-square test were applied, as appropriate, to measure the associations between variables. Risk was estimated using odds-ratios, taking dyslipidemia as the dependant variable. Significance was set at 5% (p < 0.05). All calculations were performed using GraphPad InStat version 3.01 for Windows 95 by GraphPad Software Inc. (San Diego, CA, USA).
The research project was approved by the institution's Research and Ethics Commission. All parents or legal guardians of participating children and adolescents signed an informed consent form having been instructed on the objectives and methods of the study and the laboratory tests involved.
Forty-seven point seven percent of the 109 participating children and adolescents were male while 52.3% were female. Their ages varied from 2.1 to 19.6 years, giving a mean average of 12.2 years±4.9 years and a median of 12 years.
Mean averages, standard deviations, medians and limits of variance for the serum levels of TC, LDL-C, HDL-C and TG are laid out in Table 2. Table 3 shows the patient distribution according to reference values for TC, LDL-C, HDL-C and TG concentrations. Observe that 72.5%, 20.2% and 7.3% of the children and adolescents presented TC serum levels considered desirable, borderline and elevated, respectively. Low density lipoprotein levels were desirable in 80.7%, borderline in 12% and elevated 7.3% of cases. Two patients with elevated LDL-C levels exhibited values between 160 and 189 mg/dl, which is considered excessive for individuals more than 20 years old.11 Desirable HDL-C levels were encountered in 86.2% of the sample and undesirable in 13.8%. Triglyceridemia was normal in 87.2% of cases and elevated in 12.8%, including four patients (3.6% of the sample) who exhibited levels above the level considered high-risk for adults (> 200 mg/dl).11
Across the series as a whole, 20.1% of patients presented isolated hypercholesterolemia, 0.9% isolated hypertriglyceridemia, 3.7% mixed hyperlipidemia and 13.8 % had reduced HDL-C levels, in isolation or in combination with increased LDL-C and/or TG. Thus, of the total of 109 children and adolescents with family histories of premature CAD, 42 (38.5%) presented dyslipidemia (Figure 1).
An analysis of BMI values revealed that 10.1% of the children and adolescents were obese , 15.6% presented overweight, 66.9% had normal weight and 7.4% were underweight. Lipid abnormalities were present in 57.1% (16/28) of the excess weight cases (overweight and obese) and 32% (26/55) of those whose weight was normal or who were underweight. We observed a significant association between excess weight and dyslipidemia (p = 0.02; odds-ratio 2.82; 95% CI = 1.16-6.81).
Information on family income was forthcoming in 104 cases and revealed that 76% of the families earned less than two minimum salaries per capita, per month. Fifty-two percent of the mothers had not completed schooling beyond the seventh grade while 48% had completed at least the eighth grade. Only 27.5 % (30/109) of the children and adolescents practiced physical activity either daily or two or three times a week. No associations were observed between family income, maternal education or physical activity and dyslipidemia.
Three point six percent of the patients (4/109) had a smoking habit and 2.7% (3/109) systolic arterial hypertension. Since both the number of patients who smoked and the number with arterial hypertension were small, it was not possible to assess any possible association between these factors and dyslipidemia.
Table 4 shows that 12.8% of the children and adolescents presented just one atherosclerosis risk factor and that 14.6%, 12.8% and 0.9% presented two, three and four factors, respectively, in combination with their family history of CAD. It was observed that the prevalence of dyslipidemia, in isolation or in combination with other risk factors was 38.5%.
Atherosclerotic disease, with multi factor origins, is influenced by many different genetic and environmental variables. IN our study, the children and adolescents selected presented a genetic propensity to CAD. This is considered to be one of the most important factors indicating that children over two should have their lipids profiled.9,10 It is also well established that dyslipidemia plays a significant role in the development of cardiovascular disease in adultyhood21 and that reducing serum lipid concentrations leads to a significant reduction in both cardiovascular events and mortality.22
We observed that 27.5% and 19.3% of the sample under investigation presented, undesirable TC and LDL-C levels, respectively. In a different study, also performed in São Paulo, Forti et al.16 found much higher frequencies. They studied children and adolescents from two to nineteen years of age, children of CAD patients younger than 55 who had been revascularized at the Instituto do Coração of the HC at the FMUSP, observing that 48.2% and 44.6% presented TC and LDL-C levels, respectively, above those considered ideal. In Campinas, Moura and Coronelli17 working with a sample of schoolchildren from 7 to 10 years old, who presented TC values equal to or greater than 200 mg/dl, discovered a family history of cardiovascular disease in 53.5% of cases. An investigation performed in the South of the country by Gerber e Zielinsky18 registered elevated TC values at a frequency greater than in this study. The authors of this study, in Bento Gonçalves, analyzed 1501 schoolchildren between 6 and 16 years (exclusive) detected that 38.3% had both a positive CAD family history and hypercholesterolemia. IN neither of these studies, however, was the age of CAD onset mentioned.
Research performed in other countries has reported percentages of schoolchildren with hypercholesterolemia who also had a family history of premature CAD varying from 14 to 21.5%.23-25 A Danish study of children whose fathers had died of ischaemic heart disease younger than 45, found that just 6% presented elevated CT values.26 Beigel et al.,27 studying the descendents of CAD patients diagnosed at 40 years of age, did not find significant differences in TC or LDL-C serum concentrations in relation to a control group, but did find differences in apoproteins concentrations.
It is probable that the differences between the observed frequency of hypercholesterolemia among children and adolescents with family histories of CAD, in addition to genetic influences and biological variation, may also be determined by environmental factors, primarily family eating habits and the socio-economic variations between the populations of many different geographic regions.
In the sample currently in question, reduced HDL-C concentrations were detected in 13.8% of patients. This data is similar to that returned by another study in which reduced HDL-C values were found in 13.5% of children aged form 2 to 12 and in 14.2% of adolescents, both groups with family histories of premature CAD.16 Research suggests that reduced HDL-C concentrations accelerate the progress of atherogenesis. Necropsy findings have revealed that HDL-C concentrations, prior to death, were lower in cases that had presented atheromas when compared with cases not involving this type of lesion.6 High density liporotein concentrations below the ideal are commonly associated with heredity, other atherogenic lipoproteins and obesity.28 Within our sample six of the 11 obese children (54.5%) presented reduced HDL-C levels in association with elevated triglyceride levels. Of these six, three also presented undesirable TC and/or LDL-C levels.
Thirteen percent of our patients had triglyceride levels above those considered ideal for their ages. This data is in agreement with other researchers who found elevated triglyceridemia in 14% of a group of children and adolescents with family histories of premature CAD.15 Current thought entertains the hypothesis that certain triglyceride-rich lipoproteins may be independently involved in atherosclerosis development. Necropsy findings have shown an association between increased TG and very low density lipoprotein concentrations with fatty streaks and fibrous plaques in coronary arteries.6
Our study found dyslipidemia in 38.4% of cases (Table 4) and was unable to determine whether lipid abnormalities were dependent on genetic and/or environmental factors. Isolated hypercholesterolemia was the type of dyslipidemia most common. This is probably suggestive of the influence of family eating habits and lifestyle.
We observed that children and adolescents with excessive weight had a 2.8 times greater risk of dyslipidemia. This data agrees with Forti et al.16 who found a significantly higher frequency of undesirably high TC values among children and adolescents with excessive weight and a family history of premature CAD. A longitudinal study performed in the city of Bogalusa9 showed that the descendents of individuals who had presented CAD before reaching 50, were more obese than individuals with no family history and that this obesity had onset during early childhood. This being so weight control becomes extremely important during childhood and adolescence since obesity, in addition to being an independent risk factor for atherogenesis, can also be associated with a series of other atherosclerotic disease risk factors, such as arterial hypertension, diabetes mellitus type 2 and dyslipidemia.5
It did not prove possible to assess any possible association between dyslipidemia and arterial hypertension or smoking, considered significant risk factors for atherosclerosis, since only three and four cases, respectively, were identified.
We observed that there was no association between dyslipidemia and physical activity, family income or maternal education. One datum that attracted our attention was the fact that less than 30% of the children and adolescents regularly practiced physical activity. A sedentary lifestyle can contribute to obesity, arterial hypertension, low HDL-C concentrations and elevated TG, all of which are recognized as factors associated with atherosclerotic disease. Indeed, physical inactivity, when present during childhood tends to continue in adult life.29
This study identified 41% of the children and adolescents as presenting between one and four atherosclerosis risk factors in conjunction with a family history of premature CAD. In general, the larger the number or severity of the risk factors, the higher the probability of the disease. Furthermore, when more than one risk factor is present, their combined effects may be multiplied and not simply added.30
Our data suggests that lipid profiling, along with the investigation of other atherosclerosis risk factors, should always we performed for children and adolescents with family histories of premature CAD.
Concluding, we can state that atherosclerotic disease prevention must be started in early childhood and that pediatricians should be alert to its risk factors in order that they be identified early and intervention in the form of preventative health programs which would cover healthy eating habits and lifestyle.
We are grateful to Prof. Dr. Cláudio Leone for co-operation with the statistical analysis and to Mrs. Lilia F. de Abreu Ferreira, Volunteer at the Instituto do Coração of the HC at the FMUSP, for her assistance.
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Ceres C. Romaldini
Instituto da Criança do Hospital das Clínicas
Faculdade de Medicina da Universidade de São Paulo
Av. Dr. Eneas Carvalho Aguiar, 647
CEP: 05403-900 - São Paulo, SP, Brazil
Phone: +55 (11) 3069.8527 - Fax: +55 (11) 5051.2477
Manuscript received Mar 25 2003, accepted for publication OCT 29 2003