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Metabolic Syndrome and CVD Risk in College Students?
Exercise and Health
Fitness and Fatness: Indicators of Metabolic Syndrome and Cardiovascular Disease Risk Factors in College Students?
JANELLE SCHILTER1, LANCE DALLECK1,2
1Department of Human Performance/Minnesota State University, Mankato, MN, USA, 2Department of Sport and Exercise Science, The University of Auckland, Auckland, New Zealand
ABSTRACT
Schilter JM, Dalleck LC.Fitness and Fatness: Indicators of Metabolic Syndrome and Cardiovascular Disease Risk Factors in College Students? JEPonline2010;13(4):29-39.The purpose of this study was to identify which health related behaviors including fatness, amount of physical activity, and cardiorespiratory fitness, correlate with increased cardiovascular disease and metabolic syndrome risk factors in college students. There were 203 men and women (20.3 2.2 yr) who participated in a two day collection period. Height, weight, waist circumference, blood pressure, blood lipid profile, and cardiorespiratory fitness were measured. Each participant also filled out a questionnaire in regards to their physical activity habits and other demographic information. Multiple linear regression was used to determine the independent relation of fatness (body mass index and waist circumference), amount of physical activity, intensity of physical activity, and cardiorespiratory fitness to metabolic syndrome and cardiovascular disease risk factors. Thirty-four percent of the sample population had no cardiovascular risk factors, 28.6%, 22.7% and 14.8% had one, two, and three or more risk factors respectively. Physical activity and fatness were predictive of low cardiorespiratory fitness and dyslipidemia. Individuals that self-reported vigorous (n=55) rather than moderate (n=134) physical activity levels had significantly (p<0.05) higher VO2max, lower resting heart rate, higher HDL, and lower fasting blood glucose. These findings suggest that multiple cardiovascular risk factors are present in a college aged population. The relationship between physical activity and fatness suggest that future prevention programs should focus on modifying these behaviors
Key Words:Physical activity, Obesity, Prevention, Young adults
INTRODUCTION
In 2006, according to the American Heart Association (AHA), about 80 million people in the United Stated had some sort of cardiovascular disease (CVD), while claiming 35.3% of all cause death (24). As of 2007, the AHA also notes that 35.7% of the U.S. population has Metabolic Syndrome (MetS), which is defined as a grouping of metabolic abnormalities including glucose intolerance, insulin resistance, central obesity, dyslipidemia, and hypertension. In 2004, MetS affected 34.6%, 76 million individuals, of the population (24). Over nine percent, about 2.9 million of adolescents, ages 12–19, have MetS. Forty-four percent of children who are overweight or obese have MetS (24). Consequently, risk factors for MetS are known to increase the risk of CVD (11).
While researching prevalence of MetS, Huang et al. discovered a low prevalence among college aged students, but it was shown that 26-40% of students had at least one risk factor. High-density lipoprotein (HDL) cholesterol, impaired fasting glucose, and hypertriglyceridemia had increased prevalence among this population. While females in Huang et al.’s study were more likely to show impaired glucose tolerance, men showed more cases of obesity, hypertension, and hypertriglyceridemia (17). A major problem with young people and risk is their overall lack of awareness. For example, Collins et al. and Green et al. discovered that most college students do not accurately perceive their risk of heart disease and would rate their own risk less than their peer’s risk.Additionally, lack of knowledge among college students in regards to risk factors is an issue (7,15). Becker and colleagues discovered that college students were unsure which risk factors will develop into MetS (2). Due to the fact that college students are unaware and have lack of knowledge on MetS and CVD risk factors, it is likely that they will go undiagnosed until cardiovascular problems occur.
Physical activity is important in aiding in the prevention process of CVD and MetS. With age, college students tend to see a decrease in physical activity (16, 38); nationally 22.4% of 18-24 year olds report participating in no physical activity, but Huang et al. only saw 16.1% of their subjects participating in no physical activity (16). After follow up of a nine year longitudinal study, Xiaolin and colleagues found that both men and women, aged 15-39, had a linear relationship between leisure time physical activity and MetS for all definitions (42). Spencer found that lack of cardiovascular exercise increases cholesterol levels (40). MetS may be prevented or delayed with physical activity throughout a lifespan (42). Diseases that are associated with physical inactivity can be reduced by slightly increasing the amount of physical activity above the minimal recommendations (39). The AmericanCollege of Sports Medicine states that participation in regular physical activity can decrease the risk of both fatal and nonfatal cardiovascular disease events and “the benefits of regular physical activity outweigh its risks” (1). A sedentary lifestyle, along with poor cardiorespiratory fitness has been shown to be associated with an increased risk of MetS in middle aged men (22). Janssen and colleagues discovered that adolescent individuals with high cardiorespiratory fitness levels were associated with lower MetS prevalence (19). With implementation of exercise, risk factors of MetS can be reversed and prevented (12).
Hypertension, renal dysfunction, unhealthy lipid profiles, metabolic dysfunction, and impaired insulin resistance are just some of the problems that are occurring in obese individuals (21). Colleges across the United States are seeing increasing obesity rates (35). Fifty percent of children who are overweight tend to be overweight as an adult; these children also have a tendency to have a collection of risk factors for CVD (21). Elevated risk for MetS and CVD are being seen in the younger population, which may in turn cause many health problems later in their lives. College students who were overweight had a threefold increased risk of obtaining at least one MetS risk factor (18). Likewise, obesity has been shown to increase hypertension, which is a risk factor for both CVDand MetS (33). Due to sedentary lifestyle choices, there is a growing prevalence of childhood obesity.Obesity, along with insulin resistance, has been shown to play a vital role in the development of MetS (5). Due to increased visceral fat, insulin resistance and elevated lipid levels accelerate the atherosclerosis process (10,23,30). In addition, the association between waist to hip ratio/waist girth was directly associated with an increased occurrence of coronary calcification fifteen years later (23). As illustrated above, increased body weight increases the risk factors associated with MetS and CVD.
There is evidence that suggests that the presence of MetS is a strong predictor of CVD development (9,10,13,14,15,25,26,28,36). Lloyd-Jones and colleagues, found that the lifetime cardiovascular risk was very low if no risk factors were present (25). Identification and management of MetS is an extremely important piece in the prevention of coronary heart disease (24). The association between MetS and CVD are strongly related because they share many of the same risk factors; the risks that define MetS tend to lead to development of CVD (36).
The focus of both students and universities should be on preventing risk factors from occurring in the first place.Regardless of their young age, college students are at risk for developing risk factors of MetS and CVD diseases (17,18).The lifestyle choices that are made during the college years may be influencing development of risk factors. Therefore, the purpose of this study was to identify which behavior-related risk factors including fatness, amount of physical activity, and cardiorespiratory fitness correlate with increased CVD and MetS risk factors in college students.
METHODS
Subjects
The subjects recruited in this study consisted of 203 college students (78 male and 125 female)from an upper Midwest university, where the total student body population is about 10,000. Of the participating students 95.2% were Caucasian, 1.0% Hispanic American, 2.4% Asian American and 1.4% were from other ethnicities. A majority, 67.1%, of the sample were college freshman. Students were recruited by class announcements and further details were given to those who were interested. All of the subjects understood the terms of the study and signed a consent form agreeing to the procedures. This study was approved by the University Subjects Institutional Review Board.
Procedures
During the data collection the following measurements were taken: height, weight, waist circumference, resting HR, blood pressure, blood lipid profile, blood glucose, and aerobic fitness. The evaluation was performed by junior and senior level students, who were trained by a PhD-level exercise physiologist. On the first day of data collection, height, weight, waist circumference, resting HR, blood pressure, blood lipid profile, and blood glucose were collected. First, height was measured in centimeters and inches using the Seca stadiometer. Subjects were instructed to remove their shoes and step with their back against the wall under the stadiometer hinged lever. Subjects stood as tall as possible with their feet together; the subject deeply inhaled, and the technician positioned the hinged level to the crown of the head to find the height reading to the nearest 0.1 centimeter. Female subjects were asked to wear their hair down or in a low ponytail. To find the subject’s weight, a standard Detecto scale was used. Participants were instructed to remove shoes, jewelry, accessories, and anything in their pockets. They then stood on the scale with their arms down at their side. The technician recorded weight to the closest 0.1 kilogram.
Body mass index was calculated by dividing weight in kg by height in meters squared. Waist circumference was measured around the smallest portion of the waist, above the umbilicus and below the xiphoid process. The measurement was taken on bare skin with the tape directly on the skin without pulling too tightly to create skin compressions. The reading was recorded to the nearest 0.1 centimeter. ACSM guidelines for resting blood pressure were followed (1). Participants were seated quietly for about five minutes in a chair with their arms rested and relaxed at heart level. Blood pressure was measured twice on the left arm brachial artery with the use of a sphygomomanomter. Each measurement was separated by one minute, and the mean of the measurements was recorded. Fasting blood lipids and blood glucose tests were performed. Participants were instructed to fast for twelve hours prior to testing, as well as to refrain from exercise, caffeine, and smoking. Participants’ hands were washed with soap and water, and then wiped with an alcohol swab and allowed to dry. Following a 10 minute upright sitting rest, skin was punctured using lancets. Blood from the fingerstick sample was collected into a heparin-coated 40l capillary tube. Blood was then dispensed onto test cassettes for analysis with a LDX Cholestech analyzer, which measured total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, triglycerides, and blood glucose). The analyzer was checked prior to use for that day with an optics check.
As participants were leaving, they were given a short questionnaire investigating their family health history, personal health history, amount of physical activity completed and intensity, and current medication usage. Amount of physical activity (minutes/week) completed by each subject was obtained by multiplying numbers of days completed and minutes per exercise session. Demographic information such as age, gender, ethnicity, and year in school was also collected within the questionnaire. All subjects brought questionnaire back to their second data collection session. The second day of data collection, within a six week collection period, consisted of a cardiorespiratory fitness test. Participants completed a one mile walk test around the track. Based on the subject’s heart rate, VO2 max was estimated. The cut off values for each of the independent variables are shown in Table 1. These were obtained from the ATP III (Adult Treatment Panel III) definition of MetS, while the remaining independent variables including body mass index, physical activity, and LDL cholesterol cut off levels were taken from the American College of Sports Medicine which is outlined elsewhere (1).
Statistical Analyses
All analyses were performed using Statistical Package for the Social Sciences, Version 15.0. (SPSS Inc., Chicago, IL). Measures of centrality and spread are presented as frequency and mean ± SD. MetS guidelines, according to the NCEP-ATP III, were used to determine cut off values for risk factor stratification; these are outlined in Table 1. Use of a multiple linear regression analyses was used to determine the independent relation of fatness (body mass index and waist circumference), participation in physical activity, and cardiorespiratory fitness level to MetS risk factors.MetS risk factorswere entered as the dependent variable, while amount of physical activity, cardiorespiratory fitness level, and fatness were entered as independent variables. Residual analyses to test the validity of regression model assumptions were performed for all developed regression models.An independent t-test was used to analyze the differences between vigorous and moderate intensity exercise. The probability of making a Type I error was set at p0.05 for all statistical analyses.
RESULTS
College aged students, 18-24 years of age, were assessed for presence of MetS and CVD risk factors. Age, height, weight, body mass index, waist circumference, resting HR, systolic and diastolic blood pressure, lipid profile, physical activity (min/week), and VO2 max were measured and shown in Table 2.
Thirty-four percent of the sample population had no cardiovascular risk factors, 28.6%, 22.7% and 14.8% had one, two, and three or more risk factors respectively as shown in Table 3. Dyslipidemia, physical inactivity, and fatness were among the risk factors that were most commonly found within the sample population. Physical activity (R2 = .64) and fatness (R2 = .40) were shown to be predictive of low cardiorespiratory fitness and dyslipidemia. Individuals that self-reported vigorous (n=55) rather than moderate (n=134) physical activity levels had significantly (p< 0.05) higher VO2max, lower resting heart rate, higher HDL, and lower fasting blood glucose as shown in Figure 1.
DISCUSSION
Considering the rising amount of individuals who are experiencing CVD and MetS throughout their lifetime (24), it is crucial to implement healthy lifestyle practices at an early age (31). Understanding which health risks most greatly affect risk for CVD and MetS in college aged adults is yet to be determined. Therefore, the main purpose of this study was to examine which health related behaviors including fatness, amount of physical activity, and cardiorespiratory fitness, correlate with increased CVD and MetS risk factors in college students. The results of this study suggest that there are lifestyle behaviors that will hinder one’s cardiovascular health.
The findings of this study suggest that multiple CVD risk factors are present in the college aged population. Most notably found were dyslipidemia, physical inactivity, and obesity. Only 34% of the sample population had no risk factors, leaving almost two-thirds with one or more risk factors.Similar to this study, previous research has shown that CVD and MetS risk factors are present in college students (17,18,40). Huang and colleagues reported 33% of students obtained at least one risk factor for MetS; abnormal HDL cholesterol was seen in 24% and impaired fasting glucose in nine percent of the participants (17), this is comparable to what was found in the present study.
With 38% of the sample population having low HDL levels, it is important to highlight the various cardioprotective mechanisms of HDL. In both genders, at all ages and at all levels of risk, HDL cholesterol protects against cardiovascular disease by increasing reverse cholesterol transport, inhibiting inflammation, and reducing oxidation (8). A significantly strong inverse relationship has previously been reported between HDL cholesterol and CVD within both genders (8). Young adults with low HDL cholesterol levels have been shown to have 28-fold higher odds of having a myocardial infarction (34).In conclusion, low HDL is a significant indicator of future CVD, and with appropriate lifestyle modifications, increases in HDL may play a crucial role in CVD prevention (8,34).
In this study, individuals who self-reported higher amounts of physical activity and had decreased fatness were significantly associated with elevated cardiorespiratory fitness levels and reduced dyslipidemia. Huang discovered that dyslipidemia was associated with being overweight in college aged students; even at a young age, being overweight and having a poor metabolic profile contribute to a major health threat (18). Due to sedentary lifestyles, obesity has become a large health problem; abdominal obesity is strongly related to development of CVD (10). A 15 year longitudinal study completed by Lee and colleagues discovered that abdominal obesity was associated with early atherosclerosis development (23). This demonstrates the importance of decreased fatness, especially abdominal fatness, on cardiovascular health. An increased amount of physical activity was shown to be beneficial on a lipid profile and prevention of metabolic decline (20,39). The AmericanCollege of Sports Medicine states that both fatal and nonfatal cardiovascular events can be decreased by regular exercise, and the risk is outweighed by the many benefits (1). Implementation of a prevention program, concentrating on increasing amount of physical activity completed and decreasing amount of body fatness, in college universities, may be crucial in prevention of future CVD and MetS.