The Extended Relationship between Child Cardiovascular Risks and Academic Performance Measures

Authors


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Department of Pediatrics, West Virginia University, PO Box 9214, RCBHSC, Morgantown, WV 26506-9214. E-mail: lcottrell@hsc.wvu.edu

Abstract

Objective: To examine the relationship between children's overweight status and other cardiovascular risk fitness factors and academic performance among fifth-grade students.

Research Methods and Procedures: Using a sample of 968 fifth-grade students (50.7% boys; mean age = 10.6 years), children's cardiovascular risks (BMI, blood pressure, acanthosis nigricans) and fitness measures were compared with their mean group performance scores across four subscales (mathematics, reading/language arts, science, and social studies) of a statewide standardized academic performance test.

Results: Of this sample, 39% were either at risk for being overweight or were already overweight; slightly over one half were of normal weight. Initial findings revealed a significant relationship between children's weight category and their reading/language arts, mathematics, and science test scores even after controlling for a proxy of socioeconomic status. When additional cardiovascular risk and fitness measures were included in the model, however, children's BMI status had no association. Instead, a composite fitness index, children's blood pressure, sex, and proxy of socioeconomic status were significantly associated with children's academic test scores.

Discussion: This study expanded our understanding of the connection between children's overweight risks and academic performance by examining the impact of other cardiovascular risk factors such as high blood pressure and measures of fitness. These findings support the development and implementation of childhood cardiovascular risk surveillance programs that evaluate not only children's overweight risks but also their fitness, risk for type 2 diabetes, and/or high blood pressure by showing a relationship between some of these risks and children's academic test performance.

Introduction

To date, a significant body of evidence has been collected documenting an alarming increase in the prevalence of overweight (≥95th percentile in BMI for age and sex) among children and adolescents nationally and worldwide (1)(2)(3)(4). Prevalence reports of this issue vary by ethnicity, region, and sex; however, most findings show that at least 10% of our children and adolescents are already overweight (2). In turn, researchers have set out to better understand the impact of the risks of overweight on other aspects of children's physical, emotional, and cognitive development (5)(6)(7).

For over a decade, studies have documented associations between child overweight and children's physical and emotional health concerns including type 2 diabetes, hypertension, dyslipidemia, hyperinsulinemia, depression, and anxiety (5)(6)(7)(8)(9)(10)(11)(12). However, information about relationships between childhood BMI status and children's cognitive functioning and development has been limited. In a recent review, Taras and Potts-Datema (13) described and compared 10 studies conducted over the past decade, all with the goal of examining the relationship between child overweight and school performance. Considering outcomes such as academic achievement test performance, measures of intelligence, and school attendance, the authors identified strong evidence for an inverse association between child overweight and academic performance across diverse samples of children and adolescents (14)(15)(16)(17)(18). However, like others, Taras and Potts-Datema argued that childhood overweight issues were a marker, not a causal factor, of poor academic performance (13)(14)(15)(16)(17)(18).

Studies based on child and adolescent samples have shown that when certain demographic (e.g., socioeconomic status), environmental (rural area), and behavioral (e.g., number of hours in sedentary behavior) variables are considered, the effect of overweight on children's academic performance weakens (15)(17). Additional psychosocial variables such as low self-esteem and depression are related to child overweight but could also be associated with children's performance on tests and their school attendance (19). Although several variables have been examined in terms of their impact on children's cognitive development (as measured by their academic performance), we have yet to incorporate additional indices of children's health such as blood pressure and diabetic status. Furthermore, despite concerns about the use of BMI as a measure of overweight, only a few studies have incorporated additional measures of child fitness to explore potential associations with child academic performance (20).

This study examined the relationship between childhood overweight risks and children's academic performance on four standardized subscales: mathematics, reading/language arts, science, and social studies. Children's BMI, blood pressure status, acanthosis nigricans (AN),1 and total fitness score on the FITNESSGRAM were examined after controlling for child sex and financial need.

Research Methods and Procedures

Participants

All students (N = 1000) enrolled in fifth-grade classrooms within a rural, primarily white area in West Virginia were eligible to participate in this study through passive school-based consent procedures. Information about the participants’ backgrounds and demographics (except for child age and sex) was not available because of the passive nature of the consent process. Specifically, parents were informed of the screening procedures at the beginning of the school year and asked to inform investigators only if they did not wish for their child to participate in the study.

Measures

Children's Weight Status

The children's height (in) and weight (lb) were measured using the Shorr Infant/Child/Adult Height/Length Board and the SECA 880 Floor Digital Scale (Hanover, MD). Children's weight status was measured by calculating their BMI. The BMI for each child was calculated using the equation recommended by the Centers for Disease Control and Prevention (21): weight (in pounds)/[height in inches)]2 × 703. All weight percentile categories (underweight, normal-weight, at-risk-for-overweight, and overweight) were based on the age- and sex-specific growth charts recommended by the Centers for Disease Control and Prevention (22)(23). BMI values less than the 5th percentile were classified as underweight; BMI values between the 5th and 84.9th percentile were classified as normal-weight; at-risk-for-overweight was based on a BMI at the 85th to 94.9th percentiles; and the overweight categorization was based on ≥95th percentile.

Children's Cardiovascular Risk Markers

Children's blood pressures were measured using the Tycos Welch Allyn cuff (Welch Allyn, Inc., Skaneateles Falls, NY). Blood pressure was assessed once during the screening period. If considered a high reading, the school nurse rechecked it at a later date, and the lower of the two readings was recorded. We decided to take the lower reading to control for any effects the screening procedures may have created. For example, children may become excited or anticipate the screening procedures, which, in turn, may increase their blood pressure readings. The national guidelines from the Fourth Report on Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents (24) were used to identify which children showed high systolic and diastolic pressures according to same age and sex distributions, with 0 representing a normal reading (<90th percentile), 1 representing a pre-hypertensive reading (90th to 94.5th percentile), and 2 representing a high blood pressure reading (≥95th percentile).

Children were also screened for a potential marker of type 2 diabetes known as AN. AN presents as a thickened dark skin mark on the back of a child's neck or in the crease of the arms and can differ by grade based on the intensity of the coloration. A designation of 1 represented a positive identification of AN, whereas 0 represented no risk of AN at the time of the assessment.

Children's Standardized Academic Test Scores

Children enrolled in grades 3 through 8 and grade 10 complete the West Virginia Educational Standards Test (WESTEST) as a criterion-based reference for their academic performance. This test has been delivered and analyzed by West Virginia educators to identify areas in need of additional instruction. Four scales of academic performance, including reading/language arts, mathematics, science, and social studies, are identified and scored by the WESTEST procedures. A student is given one of five possible classifications on each subscale: 1) novice, 2) partial mastery, 3) mastery, 4) above mastery, and 5) distinguished mastery. Scores ≥3 were considered to reflect an acceptable range of mastery on a given subject.

Children's Standardized Fitness Test Scores

Children's performances on the FITNESSGRAM physical fitness test were broken down into five subscales or fitness types: 1) aerobic capacity, 2) abdominal strength, 3) upper body strength, 4) flexibility, and 5) trunk strength. The sixth FITNESSGRAM assessment, body composition, was not conducted; rather, the Centers for Disease Control and Prevention–defined BMI readings from the health screenings were incorporated. Performance on these individual scales was categorized into one of two groups: 1 = “in the healthy fitness zone” (student met or exceeded fitness target) or 0 = “needs improvement” (student failed to meet fitness target). An overall fitness score was also calculated by summing all subscales. This score ranged from 0 to 5, with higher values indicative of a higher pass rate across the fitness subscales. Scores were later categorized into four groups based on quartile cut-off scores for the multivariate analyses. All fitness scale scores correlated significantly with one another (p < 0.01).

Children's Meal Program Status

Information was collected from the West Virginia Education Information System on whether each child was enrolled in the free or reduced cost meal program. For analyses, we coded children's meal program status by using 0 for paid meal, 1 for reduced cost meal, and 2 for free meal.

Procedures

A passive permission slip was sent home with fifth-grade students 7 to 10 days before the screening. Parents/guardians were requested to send a note or call if they preferred that their child not participate in the health screenings. The school nurse explained the screenings and the screening process to the students within their classroom immediately before the screening.

On screening day, each student had a log for recording other screenings—vision, hearing, and dental assessment—with check-off slots for the cardiovascular screening information included in this study. Health screening results and FITNESSGRAM results were entered into a web-based application designed by the West Virginia Department of Education Office of Technology and Information Systems. The Office of Technology and Information Systems office also created the Excel database for statistical analysis, with information in the web-based application merged with information such as meal program status and achievement tests scores from West Virginia Education Information System. All descriptors such as school ID number, student ID number, and student birth date were removed before statistical analysis. These procedures were implemented at the county level and approved by the County Superintendent and West Virginia University Internal Review Board.

Analyses

We outlined and compared the descriptive statistics of the variables representing children's BMI, meal enrollment, mean standardized test scores, and demographics. To examine the relationship between children's BMI and academic performance, we conducted a multiple covariate ANOVA using the four subscale group means as the dependent variables, BMI category as the independent variable, and a proxy for financial assistance (school meal program enrollment) and child sex as covariates in the model. Continued study of children's overweight and academic performance was completed with additional cardiovascular risk and fitness factors entered as independent variables in a multiple covariate ANOVA model. All analyses were conducted using SPSS 15.0 (25); inferences were made from findings based on significance levels ≤0.05.

Results

Characteristics of Sample and Study Outcome Variables

Twenty-nine of the total 1000 students who were eligible to participate in this study were not screened because of parent request or long-term absence; three additional students moved out of the area before completion of the database. Therefore, a total of 968 students (50.7% boys) participated in this study. Student age ranged between 9 and 13 years; the mean age for the sample was 10.6 years. Slightly more than one half of the sample was of normal weight; 39.2% were either at risk for being overweight or already overweight (Table 1). In the entire sample, 44% of the students participated in the free or reduced cost meal program.

Table 1. . Descriptive statistics by children's BMI category
CharacteristicChildren's BMI category (N = 968)
 Underweight (n = 28; 2.9%)Normal-weight (n = 555; 57.3%)At-risk-for-overweight (n = 161; 16.6%)Overweight (n = 224; 23.1%)
  • SD, standard deviation; AN, acanthosis nigricans.

  • **

    p < 0.01

  • ***

    p < 0.001.

Participant sex, n (%)    
 Male11 (39.3)285 (51.4)79 (49.1)116 (51.8)
 Female17 (60.7)270 (48.6)82 (50.9)108 (48.2)
Meal program, n (%)    
 Paid12 (42.9)323 (58.2)90 (55.9)117 (52.3)
 Reduced cost3 (10.7)38 (6.8)8 (5.0)18 (8.0)
 Free13 (46.4)194 (35.0)63 (39.1)89 (39.7)
Fitness characteristics, n (%) passed    
 Aerobic capacity17 (60.7)349 (62.9)81 (50.3)67 (29.9)***
 Curl up19 (67.9)411 (74.1)109 (67.7)127 (56.7)***
 Upper body strength18 (64.3)377 (67.9)85 (52.8)86 (38.4)***
 Flexibility16 (57.1)393 (70.8)111 (68.9)147 (65.6)***
 Trunk lift11 (39.3)311 (56.0)92 (57.1)136 (60.7)
 Fitness total score, mean (SD)3.38 (1.71)4.01 (1.10)3.65 (1.16)3.06 (1.23)**
Blood pressure, n (%)    
 Normal28 (100.0)487 (87.7)133 (82.6)134 (59.8)
 At risk0 (0.0)44 (7.9)17 (10.6)44 (19.6)
 High0 (0.0)23 (4.1)11 (6.8)46 (20.6)***
Positive AN, n (%)0 (0.0)1 (0.2)0 (0.0)49 (21.9)***
Academic performance, mean (SD)    
 Reading/language arts2.93 (0.77)3.25 (0.99)3.20 (0.85)3.02 (0.98)**
 Mathematics3.07 (0.86)3.40 (1.06)3.30 (0.93)3.10 (0.93)**
 Science2.93 (0.95)3.36 (0.99)3.36 (0.95)3.15 (0.97)**
 Social studies3.00 (0.82)3.30 (1.01)3.22 (0.96)3.15 (0.96)**

No significant differences were found across BMI categories based on sex or meal program enrollment. However, overweight children were found to have significantly lower fitness scores compared with other children on tasks related to aerobic capacity, flexibility, upper body strength, and overall fitness (p < 0.01). Overweight children were also more likely to be at higher risk for high blood pressure (p < 0.001), AN (p < 0.001), and lower mean academic performance scores for reading/language arts, mathematics, science, and social studies (p < 0.001).

Children's meal program enrollment was significantly associated with their academic performance on all of the subscale tests (p < 0.001). Child sex was significantly associated with children's mean social studies performance (p < 0.05). These findings revealed that children who were enrolled in the free meal program had the lowest academic scores on all subscale tests, but those who were enrolled in the paid meal program scored the highest on all subscale tests. In general, boys reported higher mean subscale scores than girls.

Children's BMI and Academic Performance

Group mean subscale scores for all subjects except social studies were significantly affected by children's BMI category after controlling for financial need with the meal program enrollment proxy variable (Table 2). As noted in Table 1, the lowest subscale scores were recorded among children within the underweight BMI category, followed by children identified as being overweight, and then those who were at risk for being overweight. Overall, this model accounted for between 6% and 10% of the variance in the mean subscale test scores.

Table 2. . MANCOVA results examining associations between children's BMI category and academic performance
SourceDependent variableType III sum of squaresdfMean squareFPartial η2
  • MANCOVA, multiple analysis of covariance.

  • *

    p < 0.05

  • **

    p < 0.01

  • ***

    p < 0.001.

Meal programReading/language arts32.229132.22936.607***0.037
 Mathematics52.227152.22754.840***0.054
 Science51.600151.60057.719***0.057
 Social studies54.680154.68060.399***0.059
SexReading/language arts1.80211.8022.0470.002
 Mathematics1.29811.2981.3630.001
 Science1.47311.4731.6470.002
 Social studies3.80813.8084.206*0.004
BMI categoryReading/language arts8.34432.7813.159*0.010
 Mathematics12.49134.1644.372**0.014
 Science8.52932.8433.180*0.010
 Social studies2.93730.9791.0810.003
Sex × BMI categoryReading/language arts1.46430.4880.5540.002
 Mathematics.028130.0940.0980.000
 Science2.44830.8160.9130.003
 Social studies2.86830.9561.0560.003

Additional Cardiovascular Risk, Fitness Variables, and Academic Performance

Children's blood pressure status (i.e., normal, pre-hypertensive, high), presentation of AN, and total fitness score on the FITNESSGRAM were added to children's sex, overweight category, and meal program enrollment as independent variables in a multiple covariate ANOVA model examining children's academic performance (Table 3). Significant main effects for child sex on math (p < 0.01), science (p < 0.001), and social studies (p < 0.01) scores were noted, with boys reporting higher performance scores. Significant main effects were also found for children's blood pressure on children's mean science scores (p < 0.001) and overall fitness score on all four academic areas (p < 0.001). Specifically, these findings revealed that children with high blood pressure readings (≥95th percentile) had lower mean science subscale scores (mean = 2.98 for ≥95th percentile; mean = 3.09 for the 85th to 94th percentile; mean = 3.17 for normal-weight). Furthermore, children with lower overall fitness scores on the FITNESSGRAM had lower mean academic performance scores than other children (Table 4). We noted that with the additional variables considered, children's overweight was not associated with their academic performance. This model accounted for 6%, 10%, 12%, and 10% of the variance in children's mean reading/language arts, math, science, and social studies scores, respectively.

Table 3. . MANCOVA results examining cardiovascular and fitness variable relationships and academic performance
SourceDependent variableType III sum of squaresdfMean squareFPartial η2
  • MANCOVA, multiple analysis of covariance; AN, acanthos is nigricans.

  • **

    p < 0.01

  • ***

    p < 0.001.

SexReading/language arts1.93311.9332.2230.002
 Mathematics7.14117.1417.713**0.008
 Science11.516111.51613.451***0.014
 Social Studies8.54418.5449.666**0.010
BMI categoryReading/language arts3.76231.2541.4430.005
 Mathematics4.74531.5821.7080.005
 Science3.15731.0521.2290.004
 Social Studies0.66930.2230.2520.001
Blood pressure statusReading/language arts0.50830.1690.1950.001
 Mathematics1.61430.5380.5810.002
 Science33.056311.01913.190***0.044
 Social Studies2.54730.8490.9610.003
ANReading/language arts0.42010.4200.5220.001
 Mathematics0.78610.7860.9350.001
 Science0.02510.0250.0330.000
 Social Studies0.56810.5680.4020.001
Fitness total scoreReading/language arts15.25835.0865.850***0.018
 Mathematics24.23238.0778.724***0.027
 Science35.453311.81813.803***0.042
 Social Studies23.17137.7248.739***0.027
Meal programReading/language arts30.761130.76135.383***0.036
 Mathematics48.014148.01451.861***0.052
 Science46.784146.78454.643***0.054
 Social Studies51.473151.47358.237***0.058
Table 4. . Mean performance scores by children's overall fitness score on FITNESSGRAM
Dependent variableFitness totalMeanSE95% confidence interval
    Lower boundUpper bound
  1. SE, standard error.

Reading/language arts1.002.8060.1992.4163.195
 2.003.2460.1752.9033.588
 3.003.3660.1863.0003.731
 4.003.0670.1852.7043.430
Mathematics1.002.9130.2072.5063.320
 2.003.4480.1823.0903.806
 3.003.6160.1943.2343.998
 4.003.2430.1932.8643.623
Science1.002.5800.2002.1872.972
 2.003.1740.1762.8293.520
 3.003.4450.1883.0773.814
 4.002.9730.1872.6073.340
Social Studies1.002.8980.2032.5003.296
 2.003.4210.1783.0713.771
 3.003.5890.1903.2153.962
 4.003.2880.1892.9173.659

Discussion

The outcomes of this study expand our understanding of the relationship between children's health and their academic performance by exploring the potential relationships between children's performance and additional cardiovascular risk factors, as well as measures of children's overall fitness. As shown elsewhere (13), children's obesity status as measured by BMI had a significant and inverse association with their performance on mathematics, reading/language arts, science, and social studies standardized tests. After controlling for child sex and a financial need proxy variable, this relationship was weakened; however, children's obesity status continued to relate to their performance on all tests except for social studies topics. The weakened or absent relationship between children's obesity status and their academic performance after controlling for other factors such as socioeconomic status and parent education has been supported by previous researchers (15)(17).

Our consideration of other cardiovascular risk and fitness factors in terms of their relationship with children's academic performance was, to our knowledge, new to this area. Children with high blood pressure readings compared with children with normal or even pre-hypertensive blood pressure readings earned the lowest science scores but did not significantly differ on other test subjects. Likewise, children who obtained a lower total fitness score, which was a cumulative score of five different fitness tests, also performed at a lower level on all academic subject tests compared with children with greater fitness indices. These findings were significant even after controlling for child sex and financial need.

In a time when the number of universal BMI screening programs continues to rise, in contrast to selective screening recommendations and concerns (26), these findings may provide helpful support for the inclusion of additional cardiovascular risk detection variables to understand the association among overweight, fitness, and academic performance. One of the potential mechanisms for the relationship between child overweight and academic performance may be the children's underlying cardiovascular risks. Additional measures of children's endothelial function or vascular constriction may help elucidate the physiologic linkages between cardiovascular risk and academic performance. Social, emotional, and environmental factors may also be linked to children's fitness levels and, subsequently, their cardiovascular risks. These contextual variables should also be included in future models. Collecting additional health information (e.g., blood pressure, AN) and fitness performance data can be exhaustive of time, finances, and other resources. However, these health indices highlight potential ways in which children's less obvious health indices might impact their academic functioning.

These findings also highlight the importance of assessing and providing service to children who are underweight (BMI < 5th percentile). Despite the potential for many to perceive underweight children as healthy or without risk, researchers, clinicians, and parents must continue to evaluate the influence of malnutrition and a variety of medical, social, and environmental factors contributing to children's underweight status, fitness abilities, and academic performance. Regardless of BMI classifications, we must consider ways to increase children's opportunities for physical activity and fitness whether it is within the school curriculum or at home and in the community. These and other findings support the benefits of physical activity and fitness and can be used to inform policy change and family health decisions.

Although useful, these findings still do not imply that high blood pressure and fitness are causal factors of academic performance; additional longitudinal research is needed for that purpose. Additional studies should also investigate these variables within more elaborate models predicting children's academic performance (15), because we were not presently able to include parent and child health behaviors, a comprehensive socioeconomic index (Hollingshead), or a thorough listing of demographic variables in our model. Studies should also assess children's blood pressure values at multiple points to evaluate the consistency of these values as a marker for children's cardiovascular risk.

As the nature and impact of childhood obesity on other facets of children's development continue to be examined, the development and assessment of more comprehensive conceptual and assessment models will be needed. Identifying effective models for evaluating children's overweight and other health risks will be important to researchers, clinicians, school representatives, and families. Additional emphasis on ways to respond to children's health needs will be needed to establish a healthy curriculum structure that ensures adequate physical activity, nutrition, and cognitive growth.

Acknowledgments

The authors thank the student participants and those who assisted with student screenings. The authors also thank the Sisters of Saint Joseph Charitable Fund, the Claude Worthington Benedum Foundation, and the Bernard McDonough Foundation for funding assistance.

Footnotes

  • 1

    Nonstandard abbreviations: AN, acanthosis nigricans; WESTEST, West Virginia Educational Standards Test.

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