Journal of Physical Activity and Health, 2014, 11, 1600 -1606 http://dx.doi.org/10.1123/jpah.2013-0125 © 2014 Human Kinetics, Inc.
Official Journal of ISPAH www.JPAH-Journal.com ORIGINAL RESEARCH
Scheduled Physical Activity is Associated With Better Academic Performance in Chilean School-Age Children Raquel Burrows, Paulina Correa-Burrows, Yasna Orellana, Atilio Almagiá, Pablo Lizana, and Daniza Ivanovic Background: This study was carried out to examine the association between systematic physical activity and academic performance in school kids after controlling for potential sociodemographic and educational confounders. Methods: In a random sample of 1271 students from urban Santiago, attending 5th and 9th grade, who took the 2009 System for the Assessment of Educational Quality (SIMCE) tests, we measured physical activity habits, anthropometric characteristics, and socioeconomic status. Academic performance was measured by the standardized SIMCE tests. Logistic regressions assessed the relationship between the allocation of time to weekly scheduled exercise, potential confounding factors, and individual academic performance. Results: About 80% of students reported less than 2 hours of weekly scheduled exercise, while 10.6% and 10.2% reported 2 to 4 hours/week and more than 4 hours/week, respectively. Devoting more than 4 hours/week to scheduled exercise significantly increased (P < .01) the odds of having SIMCE composite z-scores ≥ 50th percentile (OR: 2.3, 95% CI: 1.4 to 3.6) and ≥ 75th percentile (OR: 2.1, 95% CI: 1.3–3.3). Conclusions: Better academic performance was associated with a higher allocation of time to scheduled exercise in school-age children. Keywords: academic achievement, health-related behaviors, Chile The positive effect of regular exercise on cardiovascular and mental health has been widely demonstrated.1–3 Physical activity and fitness are associated with lower cardiovascular and metabolic risk in youth and mortality in adults.4,5 In addition, regular participation in physical activity and sports is linked to better brain function, cognition and academic performance.6 Longitudinal follow-up studies and interventions have found a direct and significant relation between physical activity and academic outcomes. 7–9 The association between physical activity and academic performance is complex. A potential link between exercise and academic performance can be explained by both physiological and psychological factors such as increased blood and oxygen flow to the brain, reduction of stress, improvement of mood, and increased synaptic plasticity.10–12 Furthermore, education and socioeconomic factors could also explain the positive association with academic outcomes.13,14 For the vast majority of children and adolescents, schools provide a unique opportunity for regular and structured physical activity. In spite of this, the constant pressure from parents -to improve the academic performance of their children, and schools -to improve their success rate in the standardized tests for the assessment of the educational quality, has resulted in more hours devoted
Burrows ([email protected]) is with the Dept of Nutritional Epidemiology and Genetics, Institute of Nutrition and Food Technology (University of Chile), Santiago, Chile. Correa-Burrows is with the Dept of Nutritional Epidemiology and Genetics, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile, since late 2013. Orellana is with the Dept of Statistics, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile. Almagiá and Lizana are with the Laboratory of Biology, Pontifical Catholic University of Valparaíso, Valparaíso, Chile. Ivanovic is with the Dept of Human Nutrition, Institute of Nutrition and Food Technology (University of Chile), Santiago, Chile. 1600
to Language, Mathematics, Science and Social Sciences at expense of the time devoted to physical education. In general, it has been difficult to approach the relationship between physical activity and performance at school. This is largely due to the lack of standardized indicators to measure the quality of both individual academic performance and physical activity or fitness condition.7–9 Few studies have used standardized tests to approach the academic achievement in large urban school populations.15,16 The aim of this study was to evaluate the association between systematic physical activity and academic performance in schoolage children measured through the national standardized SIMCE (System for the Assessment of Educational Quality), after controlling for potential sociodemographic and educational confounders.
Methods Study Population and Sample Selection The target population, 187,860 children (39% of Chilean school population), included all school-age children enrolled in 5th (N = 91,663) and 9th (N = 96,197) grade in the Chile’s Metropolitan Region (MR) in 2010 and who took the SIMCE test at the end of the year 2009. They attended public, partially-subsidized and private schools from urban areas. The sampling frame of this study corresponds to the educational establishments from the urban area of MR. The sampling system was performed in 2 stages. In the first stage, 33 educational establishments accounting for 2.61% of the total urban school population (N = 1262) were randomly selected by proportional allocation according to the stratification by type of school and the levels of achievement in the SIMCE 2009 established by the Ministry of Education (high, intermediate and low). In a second stage, in each of the 33 schools all students enrolled in both grades and taking
Scheduled Exercise and Academic Outcomes 1601
the SIMCE 2009 were invited to participate in the study. A total of 1353 school-age children and their parents agreed to participate in the study and they signed the informed consent form. Eightytwo individuals were excluded because they did not provide full information on their physical activity habits, thus, the final sample included 1271 students, 94% of the original data set. This study was approved by the Committee on Ethics in Studies in Humans of the Institute of Nutrition and Food Technology (INTA), University of Chile and ratified by the Committee on Bioethics of the National Fund for Scientific and Technologic Development (FONDECYT), Chile. Subjects’ consent was obtained according to the norms for Human Experimentation, Code of Ethics of the World Medical Association. The field study was carried out during 2010.
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SIMCE Tests Academic performance (AP) was assessed through the SIMCE test, which has national coverage in Chile and is administered by the Ministry of Education. The aim of this testing is to improve the quality and equality of the educational process in the different areas covered by the national curriculum. Scores range between 0 and 400.17 To carry out this analysis, we transformed the test raw values into z-scores, and then we estimated a composite z-score, including Language, Mathematics and Science results, and taking out Social Science as this one only tests mid school students.
Anthropometric Measurements Standardized procedures were used to measure weight to the closest 0.1 Kg, using a Seca scale, and height to the closest 0.1 cm, using a Holtain stadiometer. All the instruments were verified before measuring each subject.18 BMI (Kg/m2) and Height for age were evaluated and z-scores were obtained according to CDC/NCH/USA references.19 Nutritional status was defined as follows: Underweight (z-score < –1 SD), Normal weight (z-score from –1 SD to 1 SD), Overweight (z-score from +1 SD to < 2 SD) and Obesity (z-score ≥ 2 SD).
Scheduled Exercise Scheduled exercise was measured accounting for the number of weekly hours devoted to (1) school-based physical education and (2) sport extracurricular activities that occur outside of the regular school day, either school or nonschool organized. That is, our research focused on regularly scheduled physical activity. To measure scheduled exercise, we used a questionnaire which was validated using accelerometry-based activity monitors.20 This questionnaire was administered by a researcher to all students at the time they attended the anthropometric examination. Ninth graders answered by themselves, whereas 5th graders answered with their parents’ help. In spite of this, the questions and response categories were identical in both groups.
Socioeconomic Status (SES) SES was measured using a scale based on Graffar’s modified method which was adapted to Chilean urban and rural populations.21 This scale classified the sample into 5 socioeconomic groups: 1 = High (0.3%); 2 = Mid-High (14.7%); 3 = Middle (38.3%); 4 = Mid-Low (45.6%); and 5 = Low (1.1%). However, in our analysis we merged these 5 categories into 3: High (1+2), Medium (3), Low (4+5) SES.
School Performance School performance was measure using the criteria of the Chilean Ministry of Education. Schools are divided into 3 groups (good academic standing, satisfactory, and unsatisfactory) according to the overall performance achieved by their students in the SIMCE tests.17
Statistical Analysis Data were processed using Stata for Windows 10.1 (Lakeway Drive College Station, TX, US). Statistical analysis included Chi2 for categorical variables, and variance analysis and Bonferroni test for comparison of means. Logistic regressions were used to assess the relationship between the allocation of time to scheduled exercise (exposure) and individual academic performance (outcome). Two models were considered, using SIMCE composite z-score ≥ 50th percentile and ≥ 75th percentile as dependent variables, respectively. In both models, the primary explanatory variable was the allocation of weekly hours to scheduled exercise. Models were adjusted for potential confounders, including sex, because male students traditionally show better performance in the standardized tests administered in Chile; SES, because income level and parents’ educational and occupational status are closely linked to the student’s academic outcomes;13,14 and school performance, because the school sets important parameters of the student’s learning experience (eg, preparation of teachers or availability of resources),22,23 and because strong differentials in the quality of education exist between Chilean schools with different administrative structures. Variable selection for the logistic regression models was also guided by the bivariate analyses. A P-value of < 0.05 denoted statistical significance.
Results In our sample, 79.2% of students reported less than 2 hours of weekly scheduled exercise, while 10.6% and 10.2% reported 2 to 4 hours and more than 4 hours of weekly scheduled exercise, respectively. Table 1 contains the descriptive statistics of the sample. Mean values of chronological age, performance in Language, Mathematics and Science tests, and composite performance in the 3 tests significantly increase at higher allocation of time to weekly scheduled exercise (P < .000). The proportion of physically active subjects was significantly higher among males (14%), 9th graders (18%), students attending schools with good academic standing (15.4%), and high-SES students (16%). The proportion of school-age children above selected thresholds of academic performance in the SIMCE (composite Language, Mathematics and Science) significantly increased (P < .001) at higher allocation of time to weekly scheduled exercise, as shown in Figure 1. Table 2 provides the results of the bivariate analysis which was used to identify explanatory variables of individual academic achievement. There was a significant association between performance thresholds in the SIMCE and sex (P < .01), socioeconomic level, school performance, and allocation of time to weekly scheduled exercise (P < .001). No significant differences were found for nutritional status and grade over the control groups. Table 3 shows the results of logistic regressions modeling the association between individual academic performance and scheduled exercise in school-age children, after controlling for sex, SES and school performance in the SIMCE. Devoting more than 4 hours/ week to scheduled exercise significantly increased (P < .01) the odds
Table 1 General Characteristics of the Sample by Allocation of Time to Weekly Scheduled Exercise (n = 1271) < 2 h (A) (n = 1007)
2–4 h (B) (n = 134)
> 4 h (C) (n = 130)
P-valuec
Bonferroni adjustment
12.9 ± 2.3***BC
14.7 ± 1.9
15.3 ± 1.5
0.000
ABB
Sex Male Female
500 (75.1) 507 (83.8)
75 (11.3) 59 (9.8)
91 (13.7) 39 (6.5)
0.000d
Anthropometrics BMI (z-score) Height (z-score)
0.97 ± 1.1 –0.02 ± 1.0
0.92 ± 1.0 0.13 ± 0.9
0.76 ± 1.0 0.13 ± 0.9
0.080 0.153
–0.16 ± 0.9**B***C –0.13 ± 1.0***BC –0.19 ± 1.0**B***C –0.17 ± 1.0**B***C
0.16 ± 1.0 0.12 ± 1.0 0.15 ± 1.0 0.20 ± 1.1
0.41 ± 0.8 0.40 ± 0.9 0.42 ± 0.9 0.29 ± 0.9
0.000 0.000 0.000 0.000
Socioeconomic status High Middle Low
133 (69.3) 373 (77.4) 509 (83.9)
29 (15.1) 52 (10.8) 53 (8.9)
30 (15.6) 57 (11.8) 43 (7.2)
0.000d
Grade 5th 9th
598 (91.8) 409 (66.0)
35 (5.4) 99 (16.0)
18 (2.8) 112 (18.0)
0.000d
School performance Good Satisfactory Unsatisfactory
421 (72.2) 318 (83.5) 268 (87.3)
72 (12.4) 32 (8.4) 30 (9.8)
90 (15.4) 31 (8.1) 9 (2.9)
0.000 d
Age Mean age
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Academic performance SIMCE (z-score) Language (z-score) Mathematics (z-score) Science (z-score)
ABC ABB ABC ABC
Mean ± SD. (%). c One-way ANOVA test, except as indicated. d Chi2 (Pearson). a
b Number
Figure 1 Percentage of students above performance thresholds in the National System for the Assessment of Educational Quality 2009 (combined Language, Mathematics and Science) by allocation of time to weekly scheduled exercise. 1602
Scheduled Exercise and Academic Outcomes 1603
Table 2 Association Between Performance Thresholds in the National System for the Assessment of Educational Quality 2009 (Combined Language, Mathematics, and Science) and Sociodemographic and Health Characteristics SIMCE z-score ≥ 50th percentile
SIMCE z-score ≥ 75th percentile
n
%
n
%
Overall
753
59.0
265
24.9
Sex Male Female
419 334
62.9 54.7
163 102
29.3 20.1 P = .001
P = .003a Grade 5th grade 9th grade
373 380
51.1 60.9
141 124
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P = .170 Nutritional statusb Underweight Normal Overweight Obesity
10 448 176 119
P = .643 58.8 62.0 55.2 54.6
3 166 58 38
P = .097 Socioeconomic level High Middle Low
147 309 297
76.2 63.7 49.6
452 184 117
80 115 70
77.0 48.2 38.0
104 95 550
206 47 12
39.9 15.3 5.0 P < .001
80.0 70.9 54.6 P < .001
47.9 27.1 14.8 P < .001
P < .001 Scheduled exercise >4 hours/week 2–4 hours/week 4 hours/week
2.27 [1.41–3.64]**
2.09 [1.31–3.31]**
2–4 hours/week
1.82 [1.20–2.77]**
1.39 [0.86–2.24]
Male
1.24 [0.97–1.59]
1.51 [1.10–2.06]*
High SES
1.43 [0.94–2.17]
2.48 [1.59–3.86]***
Mid SES Good performance (school) Satisfactory performance (school) Observations Downloaded by Heriot Watt Univ on 09/24/16, Volume 11, Article Number 8
Likelihood ratio
(Chi2)
Hosmer-Lemeshow Correctly classified (%)
1.08 [0.82–1.42]
1.21 [0.83–1.75]
4.59 [3.30–6.38]***
8.97 [4.78–16.8]***
1.44 [1.06–1.97]*
3.37 [1.74–6.53]***
1271
1271
187.86***
180.17***
6.88 P = .549
9.94 P = .270
67.3
76.7
Abbreviations: SIMCE, System for the Assessment of Educational Quality; OR 95% CI, Odd Ratio 95% Confidence Interval. * P < .05; ** P < .01; *** P < .001.
of females (P < .01). Likewise, 48% of High SES student fell into that group compared with 15% of low SES students (P < .001). In our models, when controlling for sex and socioeconomic status, the effect of scheduled exercise remained significant. Our findings are consistent with the results obtained by previous studies examining the link between academic outcomes and regular physical activity.7–9 Among American students aged 11 to 18 (n = 4,746), it was observed a positive association between physical activity involvement and academic achievement. In girls, both, allocation of time to weekly moderate- to vigorous- intensity physical activity and participation on sport teams were significantly associated with higher academic performance, but in males only the participation on sport teams was independently associated. In that sample, less than 25% of the students reported less than 2.5 hours/week of scheduled exercise.28 Other study performed in 3rd to 11th grade students from Texas (n = 254,000), fitness measured by 6 independent test was strongly related to academic performance measured by standardized academic test (TAKS).16 Likewise, in 9th grade students from Sweden (n = 232; 16 ± 0.4 years old), academic achievement was associated with vigorous activity in girls but association with fitness was insignificant. In boys, only fitness was significantly associated while association with intensity of physical activity was insignificant.29 Finally, in a cross-sectional study involving 2127 children attending 4th to 8th grade from northeastern US, fitness achievement measured by 5 independent tests was significantly and positively associated to the results obtained in Mathematics and English standardized tests, after controlling for nutritional status, ethnicity, gender, grade and socioeconomic status.15 Some studies suggest that a certain threshold of intensity or a minimum weekly exercise time are required to produce positive effects on academic performance.28,30 Others conclude that academic achievement is positively linked to cardiovascular fitness, suggesting that fitness may mediate the association between physical activity and cognitive performance.16,29,31 Several research studies stress the need for a better understanding of the explanatory mechanisms involved in these relations as well as the need to assess the dose-
response relation between physical activity and academic performance. However, we should keep in mind that the main goals of promoting physical activity are to improve the population’s health and to prevent and control chronic diseases. Improving academic outcomes might be considered a positive external effect. On the other hand, interpretations of dose-response relationships would be extremely complex because of the variety of factors affecting individuals’ academic performance. In Chile, the compulsory time devoted to physical exercise in both Elementary and High schools is 1.5 hours/week. In 2002–2004, 60% of public schools students had less than 2 hours/week of regular exercise, while 70% of private schools students had more than 3 hours/week, according to the results obtained from a sample of 1700 school-age children from urban Santiago attending 8th and 9th grade.32 In the overall sample, 52% of students devoted less than 2 hours to weekly scheduled exercise. Since then, the proportion with such allocation of time has remarkably increased (79.2%). Our results show that devoting more hours to physical education is not harmful in terms of academic performance. Likewise, the available evidence suggests that increasing the allocation of time to Language, Mathematics or Science at expense of physical education does not entail better academic outcomes,7–9 while the effects on students’ health are clearly negative.1–5 In spite of this, Chilean parents, education officials and school authorities still believe that improving students’ performance requires shifting hours and resources away from physical education toward time on academics.
Limitations and Strengths Several limitations should be acknowledged in this study. Participants were drawn from one region of Chile (Santiago Metropolitan Region), and may not represent other geographic regions. Nonetheless, this area accounts for more than 55% of Chilean school-age children, and our sample is representative of the target population according to type of school (private, partially subsidized and public) and school academic performance in the SIMCE 2009. Second, we measured hours of scheduled exercise regardless of the intensity
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Scheduled Exercise and Academic Outcomes 1605
of exercise or physical fitness. There is substantial evidence that both can help improve students’ academic performance. In addition, statistical association alone cannot establish causation, thus although our findings show a relationship between regular physical activity and academic performance in school-age kids, the direction of causation is still to be established. Finally, the cross-sectional nature of the study limits the ability to draw conclusions on the temporality of this relationship. In spite of these limitations, this research provides results that confirm the existence of a positive link between regular physical activity and academic performance, after controlling for confounding factors, such as sex, socioeconomic level and type of school according to the achievement level in the SIMCE. On the other hand, we estimated the weighted effect of different engagement levels in scheduled exercise on student’s academic outcomes. Furthermore, we measured students’ academic performance using a nationwide standardized test, which assess students in 4 areas: Language, Mathematics, Science and Social Science. Finally, many studies testing the relationship between academic outcomes and physical activity had difficulties to find statistically significant results because they used relatively small samples.9 Our sample, made up of 5th and 9th graders, was large enough (n = 1,271) to provide statistically significant evidence. Acknowledgments Our thanks to Camila Ibaceta for all her support during the anthropometric examination. We would like to thank to the Ministry of Education, Chile, for providing part of the data used in this research. Finally, we thank the 2 anonymous reviewers for providing helpful suggestions on the manuscript. This research received financial support from the National Commission for Scientific and Technological Research, Chile, under grant FONDECYT n° 1100431.
References 1. Penedo F, Dahn J. Exercise and well-being: a review of mental and physical health benefits associated with physical activity. Curr Opin Psychiatry. 2005;18(2):189–193. PubMed doi:10.1097/00001504200503000-00013 2. Murphy M, Blair S, Murtagh E. Accumulated versus continuous exercise for health benefit: a review of empirical studies. Sports Med. 2009;39(1):29–43. PubMed doi:10.2165/00007256-20093901000003 3. Hillman C, Erickson K, Kramer A. Be smart, exercise your heart: exercise effects on brain and cognition. Nat Rev Neurosci. 2008;9(1):58– 65. PubMed doi:10.1038/nrn2298 4. Andersen B, Harro M, Sardinha B, et al. Physical activity and clustered cardiovascular risk in children: a cross-sectional study (The European Youth Heart Study). Lancet. 2006;368:299–304. PubMed doi:10.1016/ S0140-6736(06)69075-2 5. Byberg L, Melhus H, Gedeborg R, et al. Total mortality after changes in leisure time physical activity in 50 year old men: 35 year follow-up of population based cohort. BMJ. 2009;338:b688. PubMed doi:10.1136/ bmj.b688 6. Hashim H, Freddy G, Rosmatunisah A. Relationships between negative affect and academic achievement among secondary school students: the mediating effects of habituated exercise. J Phys Act Health. 2012;9(7):1012–1019. PubMed 7. Trudeau F, Shephard R. Physical education, school physical activity, school sports and academic performance. Int J Behav Nutr Phys Activ. 2008; 5:10. doi:10.1186/14795868-5-10
8. Singh A, Uijtdewilligen L, Twisk J, Mechelen W, Chinapaw M. Physical activity and performance at school. A systematic review of the literature including a methodological quality assessment. Arch Pediatr Adolesc Med. 2012;166(1):49–55. PubMed doi:10.1001/ archpediatrics.2011.716 9. Rasberry CN, Lee SM, Robin L, et al. The association between school-based physical activity, including physical education, and academic performance: a systematic review of the literature. Prev Med. 2011;52(s1):10–20. PubMed doi:10.1016/j.ypmed.2011.01.027 10. Fleshner M. Exercise and neuroendocrine regulation of antibody production: protective effect of physical activity on stress-induced suppression of the specific antibody response. Int J Sports Med. 2000; 21(s.1): 14–19. 11. Winter B, Breitenstein C, Mooren F, et al. High impact running improves learning. Neurobiol Learn Mem. 2007;87(4):597–609. PubMed doi:10.1016/j.nlm.2006.11.003 12. Yeung R. The acute effects of exercise on mood state. J Psychosom Res. 1996;40(2):123–141. PubMed doi:10.1016/0022-3999(95)00554-4 13. Davis-Kean P. The influence of parent education and family income on child achievement: the indirect role of parental expectations and the home environment. J Fam Psychol. 2005;19(2):294–304. PubMed doi:10.1037/0893-3200.19.2.294 14. Toutkoushian R, Curtis T. Effects of socioeconomic factors on public high school outcomes and rankings. J Educ Res. 2005;98(5):259–270. doi:10.3200/JOER.98.5.259-271 15. Chomitz V, Slining M, Mcgowan R, Mitchell S, Dawson G, Hacker K. Is there a relationship between physical fitness and academic achievement? Positive results from public school children in the northeastern United States. J Sch Health. 2009;79:30–37. PubMed doi:10.1111/j.1746-1561.2008.00371.x 16. Van Dusen D, Kelder S, Khol H, Ranut N, Perry C. Associations of physical fitness and academic performance among schoolchildren. J Sch Health. 2011;81:733–740. PubMed doi:10.1111/j.17461561.2011.00652.x 17. Resultados Nacionales del SIMCE 2009. Unidad de Currículum y Evaluación, Ministerio de Educación, Santiago de Chile; 2010. 18. Gibson R. Principles of nutritional assessment. Oxford: Oxford University Press; 1990. 19. Growth curves. CDC growth charts for United States: methods and development. National Center for Health Statistics; 2000. 20. Godard C, Rodríguez M, Díaz N, Lera L, Salazar G, Burrows R. Valoración de un test para evaluar hábitos de actividad física en escolares. Rev Med Chil. 2008;136:1155–1162. PubMed doi:10.4067/ S0034-98872008000900010 21. Álvarez M, Muzzo S, Ivanovic D. Escala para medición del nivel socioeconómico en el área de la salud. Rev Med Chil. 1985;113:243–249. PubMed 22. Boyd DJ, Grossman PL, Lankford H, Loeb S, Wyckoff J. How changes in entry requirements alter the teacher workforce and affect student achievement. Educ Finance Policy. 2006;1(2):176–216. doi:10.1162/ edfp.2006.1.2.176 23. Boyd DJ, Grossman PL, Lankford H, Loeb S, Wyckoff J. Teacher preparation and student achievement. Educ Eval Policy Anal. 2009;31(4):416–440. doi:10.3102/0162373709353129 24. Jiménez-Pavón D, Ortega F, Ruiz J, et al. Influence of socioeconomic factors on fitness and fatness in Spanish adolescents: The AVENA study. Int J Pediatr Obes. 2010;5:467–473. PubMed doi:10.3109/17477160903576093 25. Mason B, Mason D, Mendex M, Nelson G, Orwig R. Effects of topdown and bottom-up elementary school standards reform in an underperforming California district. Elem Sch J. 2005;105(4):353–376. doi:10.1086/429947
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26. Schneider M. Do school facilities affect academic outcomes? Washington, DC: National Clearinghouse for Educational Facilities; 2002. 27. Datos estadísticos del proceso de admisión a las universidades chilenas del consejo de rectores y aplicación de la Prueba de Selección Universitaria. Departamento de Evaluación, Medición y Registro Educacional, Universidad de Chile. Retrieved from: http://www. demre.cl/estadisticas.htm. Accessed February 20th, 2013. 28. Fox CK, Barr-Anderson D, Neumark-Sztainer D, Wall M. Physical activity and sports team participation: association with academic outcomes in middle school and high school students. J Sch Health. 2010;80(1):31–37. PubMed doi:10.1111/j.1746-1561.2009.00454.x 29. Kwak L, Kremers S, Bergman P, Ruiz J, Rizzo N, Sjöström M. Association between physical, fitness and academic achievement. J Pediatr. 2009;155:914–918. PubMed doi:10.1016/j.jpeds.2009.06.019
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Official Journal of ISPAH www.JPAH-Journal.com ORIGINAL RESEARCH
Scheduled Physical Activity is Associated With Better Academic Performance in Chilean School-Age Children Raquel Burrows, Paulina Correa-Burrows, Yasna Orellana, Atilio Almagiá, Pablo Lizana, and Daniza Ivanovic Background: This study was carried out to examine the association between systematic physical activity and academic performance in school kids after controlling for potential sociodemographic and educational confounders. Methods: In a random sample of 1271 students from urban Santiago, attending 5th and 9th grade, who took the 2009 System for the Assessment of Educational Quality (SIMCE) tests, we measured physical activity habits, anthropometric characteristics, and socioeconomic status. Academic performance was measured by the standardized SIMCE tests. Logistic regressions assessed the relationship between the allocation of time to weekly scheduled exercise, potential confounding factors, and individual academic performance. Results: About 80% of students reported less than 2 hours of weekly scheduled exercise, while 10.6% and 10.2% reported 2 to 4 hours/week and more than 4 hours/week, respectively. Devoting more than 4 hours/week to scheduled exercise significantly increased (P < .01) the odds of having SIMCE composite z-scores ≥ 50th percentile (OR: 2.3, 95% CI: 1.4 to 3.6) and ≥ 75th percentile (OR: 2.1, 95% CI: 1.3–3.3). Conclusions: Better academic performance was associated with a higher allocation of time to scheduled exercise in school-age children. Keywords: academic achievement, health-related behaviors, Chile The positive effect of regular exercise on cardiovascular and mental health has been widely demonstrated.1–3 Physical activity and fitness are associated with lower cardiovascular and metabolic risk in youth and mortality in adults.4,5 In addition, regular participation in physical activity and sports is linked to better brain function, cognition and academic performance.6 Longitudinal follow-up studies and interventions have found a direct and significant relation between physical activity and academic outcomes. 7–9 The association between physical activity and academic performance is complex. A potential link between exercise and academic performance can be explained by both physiological and psychological factors such as increased blood and oxygen flow to the brain, reduction of stress, improvement of mood, and increased synaptic plasticity.10–12 Furthermore, education and socioeconomic factors could also explain the positive association with academic outcomes.13,14 For the vast majority of children and adolescents, schools provide a unique opportunity for regular and structured physical activity. In spite of this, the constant pressure from parents -to improve the academic performance of their children, and schools -to improve their success rate in the standardized tests for the assessment of the educational quality, has resulted in more hours devoted
Burrows ([email protected]) is with the Dept of Nutritional Epidemiology and Genetics, Institute of Nutrition and Food Technology (University of Chile), Santiago, Chile. Correa-Burrows is with the Dept of Nutritional Epidemiology and Genetics, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile, since late 2013. Orellana is with the Dept of Statistics, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile. Almagiá and Lizana are with the Laboratory of Biology, Pontifical Catholic University of Valparaíso, Valparaíso, Chile. Ivanovic is with the Dept of Human Nutrition, Institute of Nutrition and Food Technology (University of Chile), Santiago, Chile. 1600
to Language, Mathematics, Science and Social Sciences at expense of the time devoted to physical education. In general, it has been difficult to approach the relationship between physical activity and performance at school. This is largely due to the lack of standardized indicators to measure the quality of both individual academic performance and physical activity or fitness condition.7–9 Few studies have used standardized tests to approach the academic achievement in large urban school populations.15,16 The aim of this study was to evaluate the association between systematic physical activity and academic performance in schoolage children measured through the national standardized SIMCE (System for the Assessment of Educational Quality), after controlling for potential sociodemographic and educational confounders.
Methods Study Population and Sample Selection The target population, 187,860 children (39% of Chilean school population), included all school-age children enrolled in 5th (N = 91,663) and 9th (N = 96,197) grade in the Chile’s Metropolitan Region (MR) in 2010 and who took the SIMCE test at the end of the year 2009. They attended public, partially-subsidized and private schools from urban areas. The sampling frame of this study corresponds to the educational establishments from the urban area of MR. The sampling system was performed in 2 stages. In the first stage, 33 educational establishments accounting for 2.61% of the total urban school population (N = 1262) were randomly selected by proportional allocation according to the stratification by type of school and the levels of achievement in the SIMCE 2009 established by the Ministry of Education (high, intermediate and low). In a second stage, in each of the 33 schools all students enrolled in both grades and taking
Scheduled Exercise and Academic Outcomes 1601
the SIMCE 2009 were invited to participate in the study. A total of 1353 school-age children and their parents agreed to participate in the study and they signed the informed consent form. Eightytwo individuals were excluded because they did not provide full information on their physical activity habits, thus, the final sample included 1271 students, 94% of the original data set. This study was approved by the Committee on Ethics in Studies in Humans of the Institute of Nutrition and Food Technology (INTA), University of Chile and ratified by the Committee on Bioethics of the National Fund for Scientific and Technologic Development (FONDECYT), Chile. Subjects’ consent was obtained according to the norms for Human Experimentation, Code of Ethics of the World Medical Association. The field study was carried out during 2010.
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SIMCE Tests Academic performance (AP) was assessed through the SIMCE test, which has national coverage in Chile and is administered by the Ministry of Education. The aim of this testing is to improve the quality and equality of the educational process in the different areas covered by the national curriculum. Scores range between 0 and 400.17 To carry out this analysis, we transformed the test raw values into z-scores, and then we estimated a composite z-score, including Language, Mathematics and Science results, and taking out Social Science as this one only tests mid school students.
Anthropometric Measurements Standardized procedures were used to measure weight to the closest 0.1 Kg, using a Seca scale, and height to the closest 0.1 cm, using a Holtain stadiometer. All the instruments were verified before measuring each subject.18 BMI (Kg/m2) and Height for age were evaluated and z-scores were obtained according to CDC/NCH/USA references.19 Nutritional status was defined as follows: Underweight (z-score < –1 SD), Normal weight (z-score from –1 SD to 1 SD), Overweight (z-score from +1 SD to < 2 SD) and Obesity (z-score ≥ 2 SD).
Scheduled Exercise Scheduled exercise was measured accounting for the number of weekly hours devoted to (1) school-based physical education and (2) sport extracurricular activities that occur outside of the regular school day, either school or nonschool organized. That is, our research focused on regularly scheduled physical activity. To measure scheduled exercise, we used a questionnaire which was validated using accelerometry-based activity monitors.20 This questionnaire was administered by a researcher to all students at the time they attended the anthropometric examination. Ninth graders answered by themselves, whereas 5th graders answered with their parents’ help. In spite of this, the questions and response categories were identical in both groups.
Socioeconomic Status (SES) SES was measured using a scale based on Graffar’s modified method which was adapted to Chilean urban and rural populations.21 This scale classified the sample into 5 socioeconomic groups: 1 = High (0.3%); 2 = Mid-High (14.7%); 3 = Middle (38.3%); 4 = Mid-Low (45.6%); and 5 = Low (1.1%). However, in our analysis we merged these 5 categories into 3: High (1+2), Medium (3), Low (4+5) SES.
School Performance School performance was measure using the criteria of the Chilean Ministry of Education. Schools are divided into 3 groups (good academic standing, satisfactory, and unsatisfactory) according to the overall performance achieved by their students in the SIMCE tests.17
Statistical Analysis Data were processed using Stata for Windows 10.1 (Lakeway Drive College Station, TX, US). Statistical analysis included Chi2 for categorical variables, and variance analysis and Bonferroni test for comparison of means. Logistic regressions were used to assess the relationship between the allocation of time to scheduled exercise (exposure) and individual academic performance (outcome). Two models were considered, using SIMCE composite z-score ≥ 50th percentile and ≥ 75th percentile as dependent variables, respectively. In both models, the primary explanatory variable was the allocation of weekly hours to scheduled exercise. Models were adjusted for potential confounders, including sex, because male students traditionally show better performance in the standardized tests administered in Chile; SES, because income level and parents’ educational and occupational status are closely linked to the student’s academic outcomes;13,14 and school performance, because the school sets important parameters of the student’s learning experience (eg, preparation of teachers or availability of resources),22,23 and because strong differentials in the quality of education exist between Chilean schools with different administrative structures. Variable selection for the logistic regression models was also guided by the bivariate analyses. A P-value of < 0.05 denoted statistical significance.
Results In our sample, 79.2% of students reported less than 2 hours of weekly scheduled exercise, while 10.6% and 10.2% reported 2 to 4 hours and more than 4 hours of weekly scheduled exercise, respectively. Table 1 contains the descriptive statistics of the sample. Mean values of chronological age, performance in Language, Mathematics and Science tests, and composite performance in the 3 tests significantly increase at higher allocation of time to weekly scheduled exercise (P < .000). The proportion of physically active subjects was significantly higher among males (14%), 9th graders (18%), students attending schools with good academic standing (15.4%), and high-SES students (16%). The proportion of school-age children above selected thresholds of academic performance in the SIMCE (composite Language, Mathematics and Science) significantly increased (P < .001) at higher allocation of time to weekly scheduled exercise, as shown in Figure 1. Table 2 provides the results of the bivariate analysis which was used to identify explanatory variables of individual academic achievement. There was a significant association between performance thresholds in the SIMCE and sex (P < .01), socioeconomic level, school performance, and allocation of time to weekly scheduled exercise (P < .001). No significant differences were found for nutritional status and grade over the control groups. Table 3 shows the results of logistic regressions modeling the association between individual academic performance and scheduled exercise in school-age children, after controlling for sex, SES and school performance in the SIMCE. Devoting more than 4 hours/ week to scheduled exercise significantly increased (P < .01) the odds
Table 1 General Characteristics of the Sample by Allocation of Time to Weekly Scheduled Exercise (n = 1271) < 2 h (A) (n = 1007)
2–4 h (B) (n = 134)
> 4 h (C) (n = 130)
P-valuec
Bonferroni adjustment
12.9 ± 2.3***BC
14.7 ± 1.9
15.3 ± 1.5
0.000
ABB
Sex Male Female
500 (75.1) 507 (83.8)
75 (11.3) 59 (9.8)
91 (13.7) 39 (6.5)
0.000d
Anthropometrics BMI (z-score) Height (z-score)
0.97 ± 1.1 –0.02 ± 1.0
0.92 ± 1.0 0.13 ± 0.9
0.76 ± 1.0 0.13 ± 0.9
0.080 0.153
–0.16 ± 0.9**B***C –0.13 ± 1.0***BC –0.19 ± 1.0**B***C –0.17 ± 1.0**B***C
0.16 ± 1.0 0.12 ± 1.0 0.15 ± 1.0 0.20 ± 1.1
0.41 ± 0.8 0.40 ± 0.9 0.42 ± 0.9 0.29 ± 0.9
0.000 0.000 0.000 0.000
Socioeconomic status High Middle Low
133 (69.3) 373 (77.4) 509 (83.9)
29 (15.1) 52 (10.8) 53 (8.9)
30 (15.6) 57 (11.8) 43 (7.2)
0.000d
Grade 5th 9th
598 (91.8) 409 (66.0)
35 (5.4) 99 (16.0)
18 (2.8) 112 (18.0)
0.000d
School performance Good Satisfactory Unsatisfactory
421 (72.2) 318 (83.5) 268 (87.3)
72 (12.4) 32 (8.4) 30 (9.8)
90 (15.4) 31 (8.1) 9 (2.9)
0.000 d
Age Mean age
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Academic performance SIMCE (z-score) Language (z-score) Mathematics (z-score) Science (z-score)
ABC ABB ABC ABC
Mean ± SD. (%). c One-way ANOVA test, except as indicated. d Chi2 (Pearson). a
b Number
Figure 1 Percentage of students above performance thresholds in the National System for the Assessment of Educational Quality 2009 (combined Language, Mathematics and Science) by allocation of time to weekly scheduled exercise. 1602
Scheduled Exercise and Academic Outcomes 1603
Table 2 Association Between Performance Thresholds in the National System for the Assessment of Educational Quality 2009 (Combined Language, Mathematics, and Science) and Sociodemographic and Health Characteristics SIMCE z-score ≥ 50th percentile
SIMCE z-score ≥ 75th percentile
n
%
n
%
Overall
753
59.0
265
24.9
Sex Male Female
419 334
62.9 54.7
163 102
29.3 20.1 P = .001
P = .003a Grade 5th grade 9th grade
373 380
51.1 60.9
141 124
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P = .170 Nutritional statusb Underweight Normal Overweight Obesity
10 448 176 119
P = .643 58.8 62.0 55.2 54.6
3 166 58 38
P = .097 Socioeconomic level High Middle Low
147 309 297
76.2 63.7 49.6
452 184 117
80 115 70
77.0 48.2 38.0
104 95 550
206 47 12
39.9 15.3 5.0 P < .001
80.0 70.9 54.6 P < .001
47.9 27.1 14.8 P < .001
P < .001 Scheduled exercise >4 hours/week 2–4 hours/week 4 hours/week
2.27 [1.41–3.64]**
2.09 [1.31–3.31]**
2–4 hours/week
1.82 [1.20–2.77]**
1.39 [0.86–2.24]
Male
1.24 [0.97–1.59]
1.51 [1.10–2.06]*
High SES
1.43 [0.94–2.17]
2.48 [1.59–3.86]***
Mid SES Good performance (school) Satisfactory performance (school) Observations Downloaded by Heriot Watt Univ on 09/24/16, Volume 11, Article Number 8
Likelihood ratio
(Chi2)
Hosmer-Lemeshow Correctly classified (%)
1.08 [0.82–1.42]
1.21 [0.83–1.75]
4.59 [3.30–6.38]***
8.97 [4.78–16.8]***
1.44 [1.06–1.97]*
3.37 [1.74–6.53]***
1271
1271
187.86***
180.17***
6.88 P = .549
9.94 P = .270
67.3
76.7
Abbreviations: SIMCE, System for the Assessment of Educational Quality; OR 95% CI, Odd Ratio 95% Confidence Interval. * P < .05; ** P < .01; *** P < .001.
of females (P < .01). Likewise, 48% of High SES student fell into that group compared with 15% of low SES students (P < .001). In our models, when controlling for sex and socioeconomic status, the effect of scheduled exercise remained significant. Our findings are consistent with the results obtained by previous studies examining the link between academic outcomes and regular physical activity.7–9 Among American students aged 11 to 18 (n = 4,746), it was observed a positive association between physical activity involvement and academic achievement. In girls, both, allocation of time to weekly moderate- to vigorous- intensity physical activity and participation on sport teams were significantly associated with higher academic performance, but in males only the participation on sport teams was independently associated. In that sample, less than 25% of the students reported less than 2.5 hours/week of scheduled exercise.28 Other study performed in 3rd to 11th grade students from Texas (n = 254,000), fitness measured by 6 independent test was strongly related to academic performance measured by standardized academic test (TAKS).16 Likewise, in 9th grade students from Sweden (n = 232; 16 ± 0.4 years old), academic achievement was associated with vigorous activity in girls but association with fitness was insignificant. In boys, only fitness was significantly associated while association with intensity of physical activity was insignificant.29 Finally, in a cross-sectional study involving 2127 children attending 4th to 8th grade from northeastern US, fitness achievement measured by 5 independent tests was significantly and positively associated to the results obtained in Mathematics and English standardized tests, after controlling for nutritional status, ethnicity, gender, grade and socioeconomic status.15 Some studies suggest that a certain threshold of intensity or a minimum weekly exercise time are required to produce positive effects on academic performance.28,30 Others conclude that academic achievement is positively linked to cardiovascular fitness, suggesting that fitness may mediate the association between physical activity and cognitive performance.16,29,31 Several research studies stress the need for a better understanding of the explanatory mechanisms involved in these relations as well as the need to assess the dose-
response relation between physical activity and academic performance. However, we should keep in mind that the main goals of promoting physical activity are to improve the population’s health and to prevent and control chronic diseases. Improving academic outcomes might be considered a positive external effect. On the other hand, interpretations of dose-response relationships would be extremely complex because of the variety of factors affecting individuals’ academic performance. In Chile, the compulsory time devoted to physical exercise in both Elementary and High schools is 1.5 hours/week. In 2002–2004, 60% of public schools students had less than 2 hours/week of regular exercise, while 70% of private schools students had more than 3 hours/week, according to the results obtained from a sample of 1700 school-age children from urban Santiago attending 8th and 9th grade.32 In the overall sample, 52% of students devoted less than 2 hours to weekly scheduled exercise. Since then, the proportion with such allocation of time has remarkably increased (79.2%). Our results show that devoting more hours to physical education is not harmful in terms of academic performance. Likewise, the available evidence suggests that increasing the allocation of time to Language, Mathematics or Science at expense of physical education does not entail better academic outcomes,7–9 while the effects on students’ health are clearly negative.1–5 In spite of this, Chilean parents, education officials and school authorities still believe that improving students’ performance requires shifting hours and resources away from physical education toward time on academics.
Limitations and Strengths Several limitations should be acknowledged in this study. Participants were drawn from one region of Chile (Santiago Metropolitan Region), and may not represent other geographic regions. Nonetheless, this area accounts for more than 55% of Chilean school-age children, and our sample is representative of the target population according to type of school (private, partially subsidized and public) and school academic performance in the SIMCE 2009. Second, we measured hours of scheduled exercise regardless of the intensity
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Scheduled Exercise and Academic Outcomes 1605
of exercise or physical fitness. There is substantial evidence that both can help improve students’ academic performance. In addition, statistical association alone cannot establish causation, thus although our findings show a relationship between regular physical activity and academic performance in school-age kids, the direction of causation is still to be established. Finally, the cross-sectional nature of the study limits the ability to draw conclusions on the temporality of this relationship. In spite of these limitations, this research provides results that confirm the existence of a positive link between regular physical activity and academic performance, after controlling for confounding factors, such as sex, socioeconomic level and type of school according to the achievement level in the SIMCE. On the other hand, we estimated the weighted effect of different engagement levels in scheduled exercise on student’s academic outcomes. Furthermore, we measured students’ academic performance using a nationwide standardized test, which assess students in 4 areas: Language, Mathematics, Science and Social Science. Finally, many studies testing the relationship between academic outcomes and physical activity had difficulties to find statistically significant results because they used relatively small samples.9 Our sample, made up of 5th and 9th graders, was large enough (n = 1,271) to provide statistically significant evidence. Acknowledgments Our thanks to Camila Ibaceta for all her support during the anthropometric examination. We would like to thank to the Ministry of Education, Chile, for providing part of the data used in this research. Finally, we thank the 2 anonymous reviewers for providing helpful suggestions on the manuscript. This research received financial support from the National Commission for Scientific and Technological Research, Chile, under grant FONDECYT n° 1100431.
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