Open Journal Systems

EDUCATION

Received: February 21^st 2014

Accepted: March 17^th 2015

Change in prevalence of physical and sports activities in a cohort of students

Liria T. Yamamoto-Kimura,^a María Guadalupe Alvear-Galindo,^a

Cristina Morán-Alvarez,^a Ángel Rodríguez-Pérez,^b Héctor Fernández Varela-Mejía,^c Cuauhtémoc Solís-Torres^c

^aDepartamento de Salud Pública, Facultad de Medicina, Universidad Nacional Autónoma de México

^bDirección de Vigilancia e Inteligencia Epidemiológica, Coordinación de Análisis e Investigación Epidemiológica, Secretaría de Salud del Distrito Federal

^cDirección General de Servicios Médicos, Universidad Nacional Autónoma de México

Distrito Federal, México

Communication with: Liria Yamamoto-Kimura

Telephone: (55) 5623 2445, Fax: (55) 5616 01 46

Email: liriayk@unam.mx

Background: Sedentary lifestyle is one of the worldwide problems of Public Health. Given that, physical activity has both direct and indirect effects on the mortality and morbidity on non-communicable chronic diseases. The aim was to determine the change in prevalence of sedentary lifestyle in a cohort of students.

Methods: The Universidad Nacional Autónoma de México makes an Automated Medical Examination to students. In this evaluation, the sport, physical activity and other risk factors were analyzed in students admitted in 2010 to the Faculty of Medicine that were previously analyzed in 2007.

Results: A total of 593 students were studied. The mean age was 15.1 ± 1.4 years. The prevalence of physical inactivity increased from 38.3 to 39.9 %. When stratified by gender, women were more sedentary (p < 0.05). Sports activities decreased significantly in frequency and time. In the sedentary population, the prevalence of overweight increased in men and the obesity in women. Smoking increased 4.9 % and alcohol consumption in 36.7 % in both sexes.

Conclusions: The prevalence of physical inactivity was higher compared to other countries. Smoking and alcohol consumption increased so it is necessary to follow up and implement programs of health promotion.

Keywords: Sedentary lifestyle; Body mass index; Adolescents

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Epidemiological studies have shown sufficient evidence of a causal relationship between sedentary lifestyle and the risk of developing chronic noncommunicable diseases (NCD). Since physical activity has direct and indirect effects on mortality from NCDs via other risk factors, such as obesity, diabetes and hypertension, which are health problems of great magnitude in the world's population, it is possible to note that physical inactivity is one of the most significant public health problems in the 21^st century.^1,2

In the past three decades a significant change in the lifestyle of the population has occurred. Increasing urbanization has changed not only the landscape, since the few green areas were displaced by factories and houses, and streets and highways were drawn mostly unplanned; urban inefficiency that causes preference for travel in motor vehicles, and a major lack of safety in neighborhoods, are some of the factors that determine the sedentary lifestyle in Mexico City. The upward trend in the size of food portions,⁵ food industry propaganda, the decrease in the availability and the significant devaluation of fresh food such as vegetables, fruits, and meats in exchange for an increase of high-calorie foods,³ rich in fat⁴ and salt, and low in vitamins, minerals and other micronutrients, as well as virtual recreational activities have all contributed to an obesogenic environment.

All this has caused an increase in the prevalence of obesity in populations. This is a public health problem with negative consequences for physical, mental and social health.^6,7 In 2008, at the global level it was estimated that 1.4 billion adults over 20 years of age were overweight and obese, and that each year at least 2.8 million people die from consequences of adult obesity. In addition, 44% of the burden of diabetes, 23% of ischemic heart disease and between 7 and 41% of some cancers are attributable to overweight and obesity.⁸

Unfortunately, children and adolescents are not spared this obesogenic environment. In 2010, the World Health Organization estimated that about 40 million children under five years of age were overweight and obese, with the highest percentage was in developing countries, where nearly 35 million live, and more frequently in the urban environment.8 In Mexico, one in three adolescents aged 12 to 19 are overweight or obese, representing more than six million individuals.⁹

During adolescence, significant changes in growth and development, as well as the thinking and behavior of teenagers occur, making them vulnerable to the influence of the environment in which they live; they are more exposed to virtual recreation and leisure activities, which tend to be sedentary. Therefore, much of their lifestyle depends on the socio-economic and educational position to which they belong.

Regular physical activity, understood as any activity that causes your body to work harder than normal in activities that are beyond the daily routine, has been consistently associated with various benefits, both physical and psychological, and it plays an important role in the prevention of some chronic noncommunicable diseases.¹⁰ Data from the 1999-2002 National Health and Nutrition Examination Survey in the population of the United States noted that only a third of teens aged 12 to 19 years got the recommended physical activity.¹¹ Similar results were found in studies in Spain^12-14 and Latin America.^15-17 Studies of United States university students showed that over the years vigorous and moderate physical activity levels decrease.¹⁸  

In our country, in adolescents and young adults at universities the frequency of sedentary lifestyle, athletics, and risk factors is documented.^19,20 However, there are few follow-up studies. Considering that one of the agents of change for lifestyles in the population are doctors, there has been little research about previous lifestyles of this group, because, unlike other fields of study, this is one of the most demanding, therefore it is necessary to know the change that occurs between two different times in terms of athletics and physical activity and the free time they have, as well as the frequency of some risk behaviors in students entering high school and three years later when beginning medical training.¹

Methods

The Dirección General de Servicios Médicos of the Universidad Nacional Autónoma de México, offers the Examen Médico Automatizado (EMA) each year to all new undergraduate and graduate students. This is a comprehensive health assessment instrument, composed of three documents and 210 self-report questions, which records among other topics, the students’ health conditions and lifestyles. This work was based on the information of students who entered medical school in 2010, and their 2007 EMA information was collected based on the students’ account or file numbers. The cohort consisted of the high school students from all campuses of the National Preparatory Schools and the College of Sciences and Humanities of the Universidad Nacional Autónoma de México, which corresponded to 65.3% of students graduating in 2010.

Extracurricular activities, free time, the practice of physical exercise and type of athletic activity, duration in hours and the weekly frequency, reasons for not doing exercise, body mass index, and alcohol and tobacco use, were all analyzed.

Physical activity was considered as any voluntary movement by skeletal muscles, producing an additional expenditure of energy than the body needs to maintain vital functions (breathing, blood circulation, etc.). When physical activity is planned, organized, and repeated in order to maintain or improve fitness we call it physical exercise. If, in addition, this exercise takes place within rules that combine physical activity with other characteristics of the person, it was considered athletics.²¹

An individual was classified as physically active if they undertook at least 30 minutes of exercise a day that made them sweat, and if they did it at least three times a week, and as sedentary any individual who did not perform exercise or who did it twice a week or less.
The body mass index (BMI) was calculated by dividing weight in kilograms by their height in meters squared (kg/m²). The age and sex criteria proposed by the Cartilla Nacional de Salud of the Secretaría de Salud were used. For comparison with other studies, the prevalence of overweight and obesity was estimated using the criteria proposed by Cole et al.²² These criteria proposed as the BMI cutoff, a BMI percentile value of 25 to 30 kg/m² at age 18 respectively in an international reference distribution.

An exploratory analysis of the data was performed. A Mann-Whitney U test was used for comparison of mean values ​​of BMI, lacking a distribution close to normal. The frequency of physical exercise, the different athletic activities in 2007 and 2010, and the percentage of change in those three years was estimated. A McNemar test (test of significance of changes) was used to assess changes in sedentary behavior. Likewise, it stratified by sex the inactivity rate by BMI category. The frequency of some factors such as overweight, obesity, tobacco and alcohol consumption was estimated by type of physical activity and sex. For statistical analysis statistical packages SPSS 15 and EPIDAT 3.1 were used.

Results

The prevalence of sedentary students in 2007 was 38.3% and in 2010 was 39.9%, a difference of 1.6%. However, when stratified by sex, the difference was striking, 9 of the men (4.4%) went on to become physically active and 23 of the women (4.5%) became sedentary. The change of mean BMI in men was 22.3 to 23.4 (p <0.001) and in women from 22.1 to 22.8 (p <0.001).

Figure 1 shows the change that occurred in the prevalence of physical inactivity by category of BMI in men and women. As we can see, the frequency of physical inactivity in men who were overweight increased from 2007 to 2010, but it decreased significantly among the obese. In women, inactivity increased except for those who were overweight.

Figure 2 shows the change in the frequency of exposure to certain risk factors in students by sex and physical activity: in physically active men, a decrease in overweight and alcohol consumption can be seen, but in sedentary men overweight increased, and alcohol use increased significantly. In women, both physically active and sedentary, the prevalence of overweight decreased, although consumption of tobacco and especially alcohol increased significantly. The prevalence of obesity in sedentary women was higher than in active.

The time spent per week and type of athletics that college students performed is shown in Table I, and one can see during the period the decrease in the duration of some athletics such as track running (23%), playing football ( 21.7%) and jogging (13.1%); only walking increased in frequency by 4.1%.

For the same period, the proportion of students who had three or more hours free decreased 68.6 to 63.1% and the proportion of students who had only 1 to 2 hours a day free increased from 31.4 to 36.8%. The justification given by respondents for the changes that occurred between 2007 and 2010 related to lack of exercise were: "I do not like it" from 13.6 to 12.6% (-1.2% change); "I have no time" increased from 63.8 to 68.8% (5%), and "I would but I don’t have the resources" from 22.5 to 18.6% (-3.9%).

Discussion

Tracking a cohort of adolescent students with a mean age at onset of 15 years, we see a high frequency of physical inactivity for their age, compared with the results of the 2012 Encuesta Nacional de Salud y Nutrición (ENSANUT) (22.7% nationally and 24.3% in the urban environment, in individuals of 15-18 years.⁹ By sex, women were more sedentary, as they are in ENSANUT. The increase in the prevalence of physical inactivity in the period studied was controversial, since this increase is attributed to women. However, it draws attention to the significant decrease in the percentage of various athletic activities in both sexes.

Comparing our results with the Alimentación y Valoración del Estado Nutricional en Adolescentes (AVENA) of Spain¹² conducted in students 13 to 18.5 years study, the prevalence was similar (39.9% vs 40%) and compared with studies in Argentina16 and Colombia, 5 the prevalences appear similar, however, the age of the university students was 18 to 29 years. Therefore, our findings are troubling because the same prevalence was seen in students three years younger. If we consider that as age increases the frequency of sedentary lifestyle increases, when newly admitted students experience the course load of medical training, further reducing their free time, this cohort would be most affected.

The results of physical activity (74.3% for men compared to 53.9% for women) were significant. There are various studies in our country on physical activity in the university population.^19,23 However, the lack of unanimity in the methodology applied makes comparisons difficult. However, the prevalence of active subjects of this study is similar to that of France (75% in men and 58% for women)²⁴ and less similar to that observed in Spain (71.4% for men, compared with 46.7% of women).¹²

The decrease in the prevalence of overweight, especially in men, can be explained, since the growth spurt in men begins in the middle of the second decade of life and concludes at the end of it; unlike women, who start between ten and thirteen and conclude by the middle of the second decade. That is why the prevalence of obesity mainly in women is not only maintained, but increases, as in this study.

It is known that overweight and obesity affect the poorest groups, in whom the level of economic and educational income is low.7 Obesity has been linked to frequent consumption of low cost foods, consisting of refined grains and added sugars and fats, since they are foods with high energy density (megajoules/kg) with lower cost per megajoule than other nutrient-dense foods.²⁵

The student population that joined the Faculty of Medicine has different characteristics, having a level of education above the average population of their age, hence probably lower combined prevalence of overweight and obesity (26.4% in 2007 and stating 20.5% in 2010) compared with the results showing the ENSANUT 2012: 35% in individuals aged 12-19 years.⁹ There are various studies that report the frequency of physical activity, tobacco and alcohol consumption in male and female adolescents. However, little is known about tastes and preferences and how they change. In this study we observed significant changes in behavior by sex in physical activity; the increase in men and decreased in women; the significant increase in alcohol consumption in both sexes and tobacco in women. Comparing the frequency of smoking in our study, the rate was three times lower in comparison with the AVENA study in Spain.¹²

While we know the justifications given by teens for not exercising, we still do not know if this change is due to other determinants, such as academic or socio-economic environment where the availability of resources for physical activity changes; or if is the cultural aspect, where athletics-oriented activities and exercise change depending on sex, which was not explored in this paper.

Socio-economic status of students could have an influence, because with access or membership to parks, sports fields or gyms, physical activity is facilitated. College students have resources for exercise close by, provided by the school, notwithstanding we do not know why many of them do not participate. Therefore, it is necessary to investigate its causes as well as the distances between home and place of study, the safety of places that students go, or ignorance of the benefits of physical activity. One must also consider the obesogenic environment facing young people, such as the proliferation of virtual games targeted by age and sex, and changing preferences for leisure activities and free time, such as alcohol and tobacco and other drugs, as a socializing activity for acceptance into a particular group.

Therefore physical activity and athletics programs to be developed should consider the interests that motivate adolescents to exercise, if for reasons of image, looking good, for health, and one must try to identify gender differences and especially why the proportion of women entering medicine with the highest prevalence of physical inactivity has increased.

This last point should be studied further, since the teens’ activities are mostly sedentary, except soccer. If we promote the importance of physical fitness such as: cardiorespiratory endurance, flexibility, strength and muscular endurance, motor coordination to use the senses, especially vision and hearing, along with the movement of different body parts, to develop movements with precision and smoothness that are important during adolescence; in addition to the benefits for psychological well-being, reducing stress and anxiety, increasing socialization and self-esteem of the people who do it, and the benefits for study and learning.¹⁰ If we implemented a program to develop physical fitness interspersed with academic activities, it would help increase academic achievement and student health.

Recently there has been writing on the preventable fraction of physical activity of the population, and its impact on various serious diseases such as cardiovascular disease, non-insulin dependent diabetes mellitus, breast cancer, colon cancer, and other diseases in various countries in the world.²⁶

Conclusions

The changes observed in this study on physical and athletic activity are discrete because of the short follow-up period. The cohort of students is not representative of the students entering the School of Medicine of the UNAM, since students of private schools are not included. However, the frequency of physical inactivity is a concern mainly in women.^12,27 Gender roles are distinct elements in the reasons for athletic activity, it is argued that stereotypes about physical activities affect individuals’ interests and motives. Men are more inclined towards competitive sports, while women prefer aesthetic activities.

If we analyze the areas where people live, grow and develop, such as the home, school, workplace, and places to spend free time, means of transport used, and the particular characteristics of the individual that encourage certain preferences, either by practicing more intense physical activities or otherwise being sedentary, these are elements to research and analyze to understand the speed with which sedentary lifestyle has predominated in recent decades, and which are beyond the scope of analysis in this paper.

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