Physical activity and cardiovascular risk factors in university students in the city of Leon , Mexico

Objectives: Recent changes in life style have increased obesity, smoking and sedentary habits in the entire population. Obesity and overweight frequency have trebled in Mexico in the last few decades. The presence and frequency of cardiovascular risk factors were determined in students at the Universidad DeLa Salle Bajío, both newly admitted and in advanced years. Material and methods: Anthropometric variables, serum glucose, total cholesterol levels, blood hemoglobin and hematocrit were obtained and assessed in 4814 students, 1507 recently admitted and 1507 advanced students. Results: The prevalence of obesity was 15.3%, sedentariness 33.8%, hypercholesterolemia 8.16%, smoking habits 15.8%, and alcohol consumption 12.1%. Body mass index (BMI) (23.5 ± 4 vs. 22.7 ± 4), waist/ abdomen index (0.84 ± 0.06 vs. 0.83 ± 0.06) and serum cholesterol (3.54 mmol/L ± 0.79 vs. 3.98 mmol/L ± 0.77) were greater in the advanced students (p < 0.001). BMI was associated only with the waist/abdomen index (r = 0.99, p < 0.001). Conclusions: There is a high prevalence of sedentarism, smoking and obesity in university students and these problems are more important in advanced students. Programs for integral health attention should be implemented in university students in order to avoid cardiovascular risk factors.


INTRODUCTION
The Framingham heart study was used to identify the main cardiovascular risk factors.Many other risk factors and markers besides high blood pressure, smoking, hypercholesterolemia, diabetes, and a family history of myocardial infarction have now been identified, changing our approach in the prevention and control of individual risk factors.Cigarette smoking prevalence in adolescents has increased in the last years [1], and while light smoking has remained stable in Hispanic students, heavy smoking increased significantly from 3.1% in 1991 to 6.4% in 2009 [2].Tobacco smoke is the most significant etiologic risk factor for lung cancer in current or previous smokers and has been strongly related to certain types of lung cancer, such as small cell lung carcinoma and squamous cell lung carcinoma [3,4], and bladder cancer [5].
Sedentary activities such as TV watching and low physical activity have been associated with cardio-metabolic risk factors in children and adolescents [6,7].Inactivity during adolescence may interact with genetic factors to influence body mass changes between adolescence and young adulthood [8].On the other hand, daily step counts and physical fitness levels were negatively associated with having one or more metabolic risk factors among adolescents [9].
Obesity prevalence is increasing in children and adolescents worldwide [10][11][12].Obesity and overweight frequency in Mexico have trebled in the last few decades [13].Obesity in children or adolescents predicts obesity in adult life [14], and is associated with lipid disorders, high blood pressure, type 2 diabetes mellitus, and liver diseases [15].Obesity, high blood pressure, smoking, and alcohol ingestion are more frequent in Portuguese men than in women when first admitted to university [16].In Korea, stress about academic performance is an important factor affecting the increase in cigarette smoking among adolescent males in a rural area of Korea [17].Byrd in 1996 showed that for every scholarship year, American boys are older than girls, and males are exposed more frequently to alcohol, tobacco and illegal drugs [18].In Mexico, the frequency of cardiovascular risk factors in university students has been scantily studied.

MATERIAL AND METHODS
A cross-sectional, observational and comparative study was conducted in 4814 students in the University DeLa Salle Bajío during the first six months of 2010.All students attending the medical service at the university for their annual medical check-up were included after signing an informed consent form.The protocol had been previously approved by the ethical and scientific committees of the institution.Blood samples were obtained at the annual clinical check-up.
After 10 min resting in a quiet room, blood pressure was measured twice using a mercury sphygmomanometer (Welch Allyn Tycos, USA).We followed the Mexican guidelines for hypertension detection [19].Weight and height were obtained by using a scale (Bame) with maximal capacity for 140 kg, and 2.20 m in height.The body mass index (BMI) was calculated according to the formula of Quetelet.Adolescent obesity was defined according to Saucedo [20].Abdomen circumference was obtained at the umbilicus level, and the hip circumference at the most prominent gluteal point.Values of abdomen/hip index (A/HI) of 0.94 for males, and 0.82 for females were used as cutoff [21].
Smoking habit data (at least 1 cigarette/day), and alcohol consumption (yes or no) were recorded.Physical activity performed by the students was classified as sedentary when there was no physical activity at all, or as standard physical activity when there were one or more weekly sessions.After 12 hours fasting, a blood specimen was extracted and serum glucose and total cholesterol were measured.
Statistical analysis: Means and standard deviation of the data were obtained.The differences between the newly admitted students and the advanced students were determined with the Student's t test.Differences on life style were tested by X 2 .Multiple regression tests were applied taking BMI as a dependent variable and serum glucose, cholesterol, alcoholic habit, smoking habit, abdomen/hip index, and sedentariness as independent variables.Significance was considered when p < 0.05.Stat-Soft Inc. (2000).
Statistica for Windows, Tulsa OK was utilized.

RESULTS
Of the 4921 students interviewed, only 4814 accepted to participate in the study.Table 1 shows a significant difference in most of the clinical characteristics when comparing the advanced students with the recently-admitted students.Impaired fasting glucose was found only in 17 subjects (< 1%) out of the 4814 subjects.Hypercholesterolemia was found in 393 (8.1%) subjects.Advanced students showed the highest levels of total cholesterol, as well as the greater BMI, and AH/I.BMI was associated with abdomen circumference and the abdomen/hip index (adjusted r = 0.98, p < 0.001).
Most of the students (66.1%) performed standard physical activity, while 33.9% were sedentary (Figure 1(a)).The percentage of students who accepted their alcohol consumption on a daily or a weekend basis is shown in Figure 1(b).The smoking habit was found in 15.9% (Figure 1(c)).
Alcohol drinking, smoking habits and sedentariness were present mainly in the advanced students (Table 2).

DISCUSSION
Recognizing cardiovascular risk factors in the young population may contribute to implementing preventive actions in order to decrease their morbi-mortality.An active lifestyle diminishes both obesity and cardiovascular risk factors in children [22].On the other hand, regular exercise is associated with a decrease in the smoking   and alcohol habits [23].Studies done in Brazil and Chile show that sedentary behavior in university students is associated with high serum cholesterol and triglycerides values [24][25][26].
Young smoking adults develop cardiologic incompetence, which is associated with an increased mortality [27].Resting heart rates as well as body mass index (BMI) in high school students are predictive risk factors for high blood pressure in adult life [28].
The percentage of hypercholesterolemia (8.16%) in our student population is similar to the hypercholesterolemia found in others studies [24,26].Hypercholesterolemia decreases total antioxidant capacity and increases lypoperoxides [29].
Elevated serum cholesterol, high blood pressure, and cigarette smoking are the major risk factors for ischemic heart disease [30] in young adults; carotid intimal-medial thickness is associated with total cholesterol, BMI, and waist/hip ratio [31].In this context, obesity is a public health problem that constitutes an important risk factor for cardiovascular diseases [15,32] and, as shown in several studies, adolescence obesity is a strong predictor of late obesity [14,33].The frequency of obesity in our population is greater than the frequency found in other Latin American university populations [24,25], one possible explanation for this discrepancy could be that most of the students attending our university come from different cities, and may have to change their nutrition habits.
The aforementioned explanation should lead us to further investigate the importance of changing nutrition habits, and its consequences over the body composition.Our data regarding greater body mass index, total cholesterol, abdomen circumference, hip circumference, and abdomen/hip index in the group of advanced students, together with the positive association of body mass index with abdomen circumference, indicate a greater deposit of visceral fat, and therefore greater risk of cardiometabolic diseases [34].
The smoking habit found in 15.8% of our students is similar to the study of Rabelo in Brazilian university students [24], lower than the 46% found by Chiang-Salgado in Chilean students [25] and lower than the 20% found at Shahroud in Iran [35].Smoking habit is the main cardiovascular risk factor [36], and the tendency to acquire and develop tobacco dependency is greater in adolescents [37,38], making it absolutely necessary to intervene on this population; however, the results of an interventionist program in adolescents to quit smoking reported by Moolchan show how much harder it is for adolescents to quit smoking, making it therefore crucial to innovate and reinforce programs aiming to stop smoking [39].
Student sedentariness in some South American universities [24,25] was more frequent than the sedentariness found by us.A possible explanation may be the greater importance given to compulsory sports at our university during the final years.It is important acknowledge that the physical activity data in the present study was ob-tained using questionnaires; future research should measure the physical activity by means of field tests (Cooper Test) or physical fitness tests (Treadmill test).
However, despite our students being less sedentary, the obesity frequency is similar to the obesity in Brazilian students, which makes it necessary to search for other components of exercise, such as intensity and time of exercise.It is also important to search for alternative explanations concerning obesity and nutrition habits.

CONCLUSION
There is a high prevalence of sedentarism, smoking and obesity in university students and these problems are more acute in advanced students.Programs for integral health attention should be implemented in university students in order to avoid cardiovascular risk factors.Due to the great proportion of obese subjects, it is desirable to evaluate with more precision the components of metabolic syndrome.Programs aiming at diminishing the unhealthy habits such as sedentariness, television time, smoking, and alcohol drinking need to be analyzed, innovated and reinforced in our university students.Further research should be done on the nutrition habits of adolescents and their consequences over the body composition in order to modify the lifestyle improving the fitness of the youth.

Figure 1 .
Figure 1.Life style and habits in participants.Physical activity (a), alcohol drinking (b), and smoking habits (c) of the students.Data from n = 4814.

Table 1 .
Clinical characteristics of the two groups.
BPM = beats per minute, BMI = body mass index, SBP = systolic blood pressure, DBP = diastolic blood pressure, AH/I = abdomen/hip index.Student's t test.All data expressed as mean ± SD.

Table 2 .
Physical activity, alcohol drinking, and smoking habits of the two groups of students.