PEDIATRICS Vol. 119 No. 3 March 2007, pp. e672-e680 (doi:10.1542/10.1542/peds.2006-0339)
ARTICLE |
Influence of Multiple Risk Behaviors on Physical Activity–Related Injuries in Adolescents
a Department of Community Health and Epidemiology
b School of Kinesiology and Health Studies
c Department of Emergency Medicine
d Social Program Evaluation Group, Faculty of Education
e Centre for Health Services Policy and Research, Queen's University, Kingston, Ontario, Canada
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ABSTRACT |
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OBJECTIVE. The study objectives were to (1) examine the relationship between physical activity and physical activity injuries in youth, (2) determine whether this relationship is modified by the engagement in multiple risk behaviors, and (3) determine whether this relationship is modified by the setting of the injury (school versus outside of school).
METHODS. We examined associations between physical activity and multiple risk behaviors with physical activity injuries occurring at and outside of school. The study population consisted of a representative sample of 5559 Canadian youth in grades 6 through 10 who participated in the 2001/2002 Health Behavior in School-Aged Children Survey. The exposure and outcome measures were determined from a classroom-based survey.
RESULTS. Irrespective of grade, there were strong gradient relations between physical activity participation and related injuries outside of school. Conversely, there were modest relations between physical activity participation and related injuries at school. In students in grades 6 to 8, there was no relation between multiple risk behaviors and physical activity injuries at school and a curvilinear relation between multiple risk behaviors and physical activity injuries outside of school. The opposite pattern of relationships between multiple risk behaviors and injuries was observed in students in grades 9 to 10. Irrespective of grade and setting of injury, there was no significant interaction between physical activity and multiple risk behaviors on injury risk. The results were consistent by severity of injury and for structured/organized and unstructured/informal forms of physical activity.
CONCLUSIONS. The environment moderated the relation between physical activity and related injuries in that strong risk gradients only existed outside of the school setting. Unexpectedly, there were no consistent gradients between the engagement in multiple risk behaviors and physical activity injuries or any interaction effect between physical activity exposure and multiple risk behaviors. These findings suggest that optimizing the environment would be a preferred strategy for preventing physical activity injuries compared with selectively targeting youth who engage in multiple risk behaviors.
Key Words: motor activity • wounds and injuries • risk-taking • adolescent
Abbreviations: MRB—multiple risk behavior • HBSC—Health Behavior in School-Aged Children Survey
Physical activity is associated with numerous health benefits in young people including the maintenance of a healthy body weight,1,2 an improved cardiovascular disease risk factor profile,3,4 reduced reports of depression,5,6 and a high level of confidence and self-esteem.7,8 Given the impact of physical activity on these outcomes and the increasingly sedentary life lead by many young people, increasing the physical activity level in children and adolescents has become the focus of public health initiatives across North America and Europe.9–11
One of the only negative impacts of physical activity participation is the increased risk of injuries that occurs while participating in sports.12,13 For instance, in a representative sample of 11- to 15-year-old Canadians, 64% of the medically treated injuries occurred while participants were engaged in sports and other forms of physical activity.14 Injuries are a leading cause of morbidity and the leading cause of mortality in young people.15–17 Thus, injury prevention is also a leading public health concern for pediatric populations.11,18
An important issue to address is how to increase sport and physical activity participation while simultaneously minimizing injury risk. Some obvious strategies are to increase the use and effectiveness of protective equipment19 and to modify the rules of a sport in a way that would reduce injury occurrence.20 An alternative approach to these strategies is to identify youth who are at particularly high risk of having a physical activity injury and who should be targeted for behavior modification (eg, change their risk behaviors).
Along that line of thought, a recent theme of research in adolescent injury etiology has examined the relation between the engagement in multiple risk behaviors (MRBs) and injury. MRB refers to the engagement in activities such as smoking and drug use,21 sensation seeking (eg, doing dangerous things just for fun),22 and failure to take appropriate safety precautions (eg, not wearing a helmet while riding a bicycle).22 It has consistently been reported that youth who engage in MRBs are at increased injury risk compared with youth who do not engage in these behaviors.23–25 Although we are unaware of any studies that have targeted sports injuries, it is reasonable to assume that young people who engage in risky behaviors are more aggressive risk takers in sport and, subsequently, are at greater risk of having a physical activity–related injury.
There is also interest in the features of the environment that influence injury risk in children and adolescents. School environments, for example, are influential settings for the establishment of social norms, such as risk-taking behaviors.26 Furthermore, optimization of the physical environment has the potential to minimize injury risk.27 Thus, one may expect to see a lower physical activity injury risk in a more controlled environment, such as the school.
The primary study objectives were to (1) examine the relation between physical activity and the risk of physical activity injuries in young people, (2) determine whether this relationship is modified by the engagement in MRBs, and (3) determine whether this relationship is modified by the setting of the injury (school versus outside of school). We hypothesized that the risk of injury for a given amount of physical activity would be higher in youth who engaged in MRBs compared with youth who do not engage in these behaviors. We also hypothesized that the relationship among physical activity, MRBs, and injuries would be less pronounced in a controlled environment, such as the school.
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METHODS |
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Description of Survey and Study Population
Results are based on the Canadian records from the 2001/2002 World Health Organization Health Behavior in School-Aged Children Survey (HBSC). The HBSC is a cross-sectional survey from 35 countries.28 The survey consisted of a classroom-based questionnaire. The Canadian data were collected in the first half of 2002. The sample was designed according to the international HBSC protocol in that a cluster design was used with the school class being the basic cluster, the distribution of the students reflected the distribution of Canadians in grades 6 to 10, and the sample was self-weighted.28 Samples were selected to represent distributions of schools by size, location, language, and religion. A total of 74.2% of the students selected for the study completed the questionnaire. The total sample consisted of 7266 children. We excluded those who did not respond to the exposures and outcomes of interest, which left a total of 5559.
The Canadian HBSC was approved by the Queen's University General Research Ethics Board. Consent was obtained from the participating school boards, individual schools, parents, and students. Student participation was voluntary.
Exposure Variables
Physical Activity Participation
Two physical activity exposures were considered: the amount of physical activity performed at school and outside of school. Participants were asked 4 questions regarding the number of hours per week that they usually participated in moderate-to-vigorous-intensity physical activity (eg, activities that make you out of breath or warm) in class time at school, in their free time at school, outside of school while participating in lessons or league or team sports, and outside of school while participating in informal activities either alone or with friends. For each of these questions there were 9 response categories ranging from "none at all" through "7 hours or more." The number of hours for questions 1 and 2 were summed to determine the amount of physical activity performed at school. The number of hours for questions 3 and 4 were summed to determine the amount of physical activity performed outside of school. In addition to being treated as continuous variables, the physical activity scores were placed into low (<3 hours/week), moderate (3–6 hours/week), and high (
7 hours/week) categories. These categories were chosen to represent <30 minutes, 30 to 60 minutes, and 60 minutes of physical activity per average day. Furthermore, the 2 at-school (class time and free time) and 2 outside-of-school (organized sport and informal activities) physical activity measures were considered as separate exposures to determine whether the results were consistent by type of physical activity in each setting.
MRBs
Common risk behaviors were documented as follows: current smoking (4 categories: "smoke every day" through "I do not smoke"), lifetime drunkenness (5 categories: "never" through ">10 times"), current use of seatbelts (5 categories: "always" through "never"), lifetime cannabis use (7 categories; "never" through "40 or more times"), illicit drug use (eg, ecstasy, cocaine, or lysergic acid diethylamide) during lifetime (7 categories: "never" through "40 or more times"), nonuse of condoms during most recent sexual intercourse (3 categories: "I have never had sexual intercourse," "yes," or "no"). The questions on cannabis use, illicit drug use, and condom use were only asked to grades 9 to 10 students. Responses for each item were given a point score corresponding with frequency of engagement ("never" = 0, "occasional" = 1, "frequent" = 2). The points were summed for the various items to create an MRB score (range: 0–6 points for grades 6–8 and 0–12 points for grades 9–10). In addition to being treated as a continuous variable, the MRB score was grouped into "never" (0 points in grades 6–8 and grades 9–10), "occasional" (1–3 points in grades 6–8 and 1–6 points in grades 9–10), and "frequent" (4–6 points in grades 6–8 and 7–12 points in grades 9–10) categories. The MRB scale used here was validated previously in this cohort using a confirmatory factor analysis.29
Outcome Variables
The 2 outcomes examined were self-report of a medically treated (by doctor or nurse) injury that occurred while participating in physical activity at school in the 12 months before the survey and self-report of a medically treated injury that occurred while participating in physical activity away from school in the previous 12 months. An initial question determined whether the student was injured in the past year to a degree that required medical treatment. Using a series of questions, individuals reporting 1 medically treated injury were asked about activities leading to their most serious injury and where they were when this injury happened. Individuals who reported that the most serious injury occurred while playing or training for a sports/recreational activity, biking/cycling, riding a skate scooter, skating (roller blades, skateboard, or ice skating), or walking/running were considered to have a physical activity injury. Injuries that occurred at school, including the school grounds, were considered to be school injuries. Injuries that occurred at home/in the yard, at a sports facility or field, in the street/road/parking lot, in the countryside (such as a lake, park, etc), or other locations (eg, commercial or business area) were considered to be nonschool injuries. To consider whether the results differed by injury severity, analyses were repeated after creating subcategories of severe (met any of the following: missed 1 full day of school, had an operation, or stayed in hospital overnight) and nonsevere injuries (all other injuries).30
Statistical Analysis
All of the analyses were conducted using SAS (SAS Institute, Cary, NC). The initial set of analyses considered the bivariate relation between the primary exposures (physical activity at school and outside of school, MRBs) and outcomes (physical activity injuries at school and outside of school) using logistic regression models. The second set of analyses considered the multivariate relation between the exposures and outcomes using logistic regression models. A product term (physical activity x MRB) was also included in the multivariate models to determine whether there was an interaction effect for the 2 exposures. Physical activity and MRB scores were included in the regression models as continuous variables. Full cubic polynomial models were used to determine whether the relations were linear or nonlinear in nature. Gender was treated as a covariate in all of the logistic regression models after analyses determined that gender was not an effect modifier in the relation between the exposures and outcomes. The constant and β coefficient parameters of the logistic regression models were used to calculate the probability of having a physical activity injury, which is the outcome presented in the results.
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RESULTS |
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Descriptive Information
Table 1 describes the study sample. Within both the grade 6 to 8 and 9 to 10 groups,
8% suffered a medically treated injury while participating in physical activity at school and 30% suffered a medically treated injury while participating in physical activity outside of school in the past year. The study participants averaged 5.5 hours of physical activity per week both at school and outside of school. For grade 6 to 8 youth, 24.6% and 24.8% were in the "low at school" and "low outside of school" physical activity categories, 36.3% and 35.0% were in the "moderate at school" and "moderate outside of school" physical activity categories, and 39.1% and 40.1% were in the "high at school" and "high outside of school" physical activity categories. The corresponding values for grade 9 to 10 students were 28.2%, 27.4%, 36.6%, 34.1%, 35.2%, and 38.5%, respectively. Regarding the MRB score, the majority of youth were considered to be never or occasional risk takers, with only 4.6% of grade 6 to 8 and 13.3% of grade 9 to 10 students being considered frequent risk takers (Table 2). More extensive details on the engagement in individual risk behaviors are contained within Table 2.
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Relation Between Physical Activity and Physical Activity Injuries
The relation between physical activity level and the probability of having a physical activity injury that required medical attention within the past year is illustrated in Fig 1. For physical activity injuries that occurred at school, there were modest positive relations for students in grades 6 to 8 (Plinear = .07) and grades 9 to 10 (Plinear = .04). For physical activity injuries that occurred outside of school, there were strong gradient (or dose-response) effects for youth in grades 6 to 8 (Plinear < .001) and grades 9 to 10 (Pquadratic = .04). In addition to using physical activity as a continuous variable, these analyses were performed using physical activity groups (Table 3). Regardless of grade, the likelihood of having a physical activity injury outside of school was increased in the moderate and high physical activity groups by comparison with the low physical activity groups. Significant relations were not observed for physical activity injuries occurring at school.
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The above analyses were repeated after physical activity injuries were subclassified into severe and nonsevere injuries. Without exception, the results were consistent by injury severity. The above analyses were also repeated after subclassifying school physical activity into class time and free time and physical activity outside of school into organized sport and informal activities. Again, the results were consistent with those reported in the preceding paragraph.
Relation Between MRBs and Physical Activity Injuries
Figure 2 illustrates the probability of having a medically treated physical activity injury within the past year according to MRB score. In grade 6 to 8 students, there was no significant (P = .25) relation between MRBs and physical activity injuries occurring at school. There was a curvilinear relation (Pquadratic = .01) between MRBs and physical activity injuries occurring outside of school such that the probability of injury was lowest in those who engaged in no risky behaviors, highest in those who occasionally engaged in some risky behaviors, and low in those who frequently engaged in all risky behaviors. In grade 9 to 10 students, the relation between the MRB score and physical activity injuries occurring at school was curvilinear in nature (Pquadratic =.02) such that the probability of injury was low in those who engaged in no risky behaviors, highest in those who occasionally engaged in risky behaviors, and lowest in those who frequently engaged in all risky behaviors. There was no significant (P = .64) relation between the MRB score and physical activity–related injuries occurring outside of school in grade 9 to 10 youth. These analyses shown in Fig 2 were also performed using MRB groups (Table 4). The likelihood of having a physical activity injury was not significantly higher in the occasional and frequent MRB groups, with the exception of physical activity injuries occurring outside of school for grade 6 to 8 students.
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The results in the proceeding paragraph were consistent by injury severity subcategories with the exception of the following. In grade 6 to 8 students, there was a positive relation between MRB score and severe physical activity injuries occurring outside of school, whereas the relation between MRB score and nonsevere injuries was nonsignificant. The above analyses were also consistent by subcategory of school (class time versus free time) and outside of school (organized sport versus informal activities) activities with 1 exception. In grade 9 and 10 students, the relation between MRBs and physical activity injuries occurring outside of school was positive for informal activities and negative for organized sport.
Interactive Effect of Physical Activity and MRBs on Physical Activity Injuries
The next set of analyses considered the interactive effect of physical activity level and MRBs on physical activity injuries. Irrespective of grade and location of injury, physical activity and MRB levels predicted injury; however, there was no significant interaction between physical activity and MRBs on the injury outcomes. An example of this effect is illustrated in Fig 3, which shows the gradient relation between physical activity level and physical activity injuries occurring outside of school according to level of engagement in MRBs. The intercepts of the regression lines between physical activity and injury varied by MRB level, but the slopes of the regression lines did not. This indicates that, for a given level of physical activity, the injury risk varied according to MRB level; however, the modifying effects of MRB did not vary across the physical activity range. For instance, in grade 9 to 10 students, the absolute difference in the probability of a physical activity injury occurring outside of school between never and occasional MRB participants was 9.3% for those who spent an average of 1 hour of per week participating in physical activity, 11.6% for those who spent an average of 7 hours per week participating in physical activity, and 12.1% for those who spent an average of 14 hours per week participating in physical activity. These differences were modest and not statistically significant.
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A second example illustrating the lack of interaction effect on physical activity injuries is illustrated in Fig 4. This figure depicts the relation between the MRB score and physical activity injuries that occurred at school in low, moderate, and high physical activity groups. Regardless of physical activity level, the relation between MRBs and physical activity injuries occurring at school was not significant (P > .2).
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DISCUSSION |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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This article presents a novel analysis of the correlates of physical activity injuries in adolescents. The findings indicate that gradients exist between the amount of physical activity that adolescents engage in and the occurrence of physical activity injuries. The social environment (at school versus outside of school) moderated the relation between physical activity and related injuries in that strong risk gradients only existed outside of the school setting. Unexpectedly, there were no consistent gradients between the engagement in MRBs and physical activity injuries or any interaction effect between physical activity exposure and MRB. Thus, there was little support for the hypothesis that youth who engage in risky lifestyle behaviors are at particularly increased likelihood of having a self-reported physical activity injury after controlling for the exposure to activity.
The population health framework suggests that risks for health outcomes, such as injuries, are driven by interactions between individual and contextual risk factors.31 To our knowledge, this is the first study to examine individual risk factors while simultaneously examining the roles of settings (contextual risks) as correlates of physical activity injuries in young people. Interestingly, there was strong evidence that moderate injury risk gradients in the relations between physical activity participation and related injuries were much weaker in schools settings. This observation was consistent for severe and nonsevere injuries and for structured/organized and unstructured/informal forms of physical activity. We had no information on the quality of the school environments responsible for this observation, although we speculate that this is, in part, explained by contextual factors and, in particular, enforced rules and expectations around student behavior and the supervision provided by adult role models that is present in the school setting. The Centers for Disease Control and Prevention have published a set of evidence-based school guidelines for injury prevention that speak to these variables.27 Some of the key recommendations in the Centers for Disease Control and Prevention guidelines are to establish social and physical environments that promote safety, implement health and safety education curricula and instruction, provide safe physical education and extracurricular physical activity programs, and provide staff development services that impart knowledge to promote safety.
An earlier study led us to believe that strong gradients would exist between the engagement in MRBs and physical activity injuries in adolescents. In an analysis of the 1997/1998 version of the Canadian HBSC, Pickett et al23 found a strong gradient relation between the number of risk-taking behaviors (of a possible 7 risky behaviors) that a young person engaged in and his or her likelihood of having a sports injury. That study did not control for the amount of physical activity that the participants engaged in, which is a limitation given that young athletes, at least at the college level, tend to partake in more risky lifestyle behaviors than their peers.32 Furthermore, that study used a crude additive measure of MRBs as compared with a confirmed and factor analytically derived MRB scale that was used here. Finally, the analytical approaches were different in the 2 studies in that Pickett et al23 used logistic regression that focused on categories of risk-taking behavior as exposures, whereas in the present study, we used a continuous risk behavior scale that smoothes out a mathematical function.
When we did see relations between MRBs and physical activity injuries in this study, they tended to be weak and inconsistent by grade. For instance, MRBs were not related to physical activity injuries occurring outside of the school setting in grade 9 to 10 students, whereas for grade 6 to 8 students, there was a curvilinear relation between the MRB score and physical activity injuries occurring outside of school. These age differences may be related to the different variables use to construct the risk behavior scales in grade 6 to 8 versus grade 9 to 10 students, the greater participation in most risky behaviors in the older adolescents, and/or different types of physical activity that younger and older adolescents may engage in. On the basis of the data collected, it is not possible to identify the reasons underlying the observed relationships, and these interpretations, therefore, remain speculative.
It is noteworthy that we used a global measure of risk-taking behavior that was assessed from questions on substance abuse (tobacco, alcohol, and drugs) and safety precautions (seat belt use and condom use). Thus, we did not assess risk-taking behaviors in sports and physical activity, per se, because they were not available within the survey. These risks would include things such as sliding head first in baseball or diving to head a ball in soccer. In an earlier study that considered a 9-item soccer risk-taking behavior scale, Kontos33 found that risk-taking behaviors on the soccer field were not directly related to soccer injuries in a sample of 260 soccer players aged 11 to 14 years. Consistent with these findings, a recent systematic review of risk-taking behaviors and injuries concluded that sports-related risk-taking behaviors are not associated with sports injuries in adults.34 It has been postulated that athletes who partake in thrill seeking and other risks and who are confident in their abilities are better able to handle the risks, are more likely to engage in calculated risks, and are subsequently less likely to get injured.33,34 Injuries that occur while participating in sports seem to be the only type of injuries that are not related to risk-taking behavior.34
Our results suggest that there is an increased risk of injury among youth engaging in physical activity outside of the school setting. The more time spent in activities, the greater the injury risk. These results are consistent with a wide body of literature12–14 and indicate that the risks associated with physical activity need to be considered when planning sports and other activities. Contrary to our original hypothesis, there is little evidence here that targeting high-risk youth (as inferred by their engagement in risk-taking behaviors) for behavioral modification as a primary prevention strategy would have a meaningful impact on decreasing injury rates as opposed to more general strategies aimed at the minimization of risks in physical activities and associated environments. With that being said, it is important to note that the present study was not an evaluation of behavior modification to reduce injury in high-risk youth, and there is a well-recognized risk of injury during physical activity among youth who engage in MRBs. In fact, all youth who engaged in physical activity, regardless of their engagement in risky behaviors, may need more guidance in injury prevention, particularly for activity performed outside of the school setting.
There are a number of strengths of this study including the size and scope of the analyses, the use of standard measures and survey procedures, and the anonymous nature of reporting, which should promote accuracy in responses. Limitations of this study include the use of self-reported data and the cross-sectional nature of the survey, which limits the ability to infer causal relationships about the findings. Second, although the HBSC questionnaire items have undergone extensive piloting and validation,28 the possibility of biased reporting of risky behaviors motivated by a desire to provide socially desirable responses must be recognized, as well as the potential for error in the recall of injuries over the past year. Third, the 5559 completed surveys used in our analyses represent only 57% of the potential youth who could have responded, which is further indicative of a potential responder bias introduced because of the high level of nonresponse. Finally, the HBSC survey did not collect information on whether or not the students were wearing appropriate safety equipment when they were injured, the specific times at which the physical activity injuries occurred, and the specific sports/activities the students were participating in when the physical activity injuries occurred. Information on these variables may have added further clarification to the relationships examined in this study.
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CONCLUSIONS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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The purpose of this study was to examine relationships among physical activity, adolescent risk-taking, and the occurrence of physical activity injuries at school and outside of school. Contrary to expectations, there was little evidence that youth who engage in MRBs should be selectively targeted as a primary prevention strategy for physical activity injuries. However, there was strong evidence that schools are protective settings. That is, whereas engagement in physical activity was associated with physical activity–related injuries in a graded, dose-related manner outside of school, this was not the case for the more controlled school setting. This suggests there is something about the school setting that acts as a mediator of the risk behavior-injury relationship. Although not characterized here, this mediator is most likely to involve enforced rules and expectations around student behavior and the supervision provided by adult role models that is present in the school setting. Injury prevention specialists must look to other prevention strategies to minimize risks in nonschool settings. These could include optimization of the physical environment, establishment of norms surrounding peer-group behavior, and more comprehensive strategies of adult supervision.
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ACKNOWLEDGMENTS |
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This study was supported by research agreements with the Canadian Institutes of Health Research (operating grant 2004MEP-CHI-128223-C) and the Public Health Agency of Canada (contract HT089-05205/001/SS), which funds the Canadian version of the World Health Organization-HBSC. The World Health Organization-HBSC is a World Health Organization/Euro collaborative study. The international coordinator of the 2001/2002 study was Candace Currie (University of Edinburgh, Edinburgh, Scotland), and the databank manager was Oddrun Samdal (University of Bergen, Bergen, Norway).
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FOOTNOTES |
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Accepted Oct 3, 2006.
Address correspondence to Ian Janssen, PhD, School of Kinesiology and Health Studies, Queen's University, 69 Union St, Kingston, Ontario, Canada K7L 3N6. E-mail: janssen{at}post.queensu.ca
This publication reports data solely from Canada (principal investigator: Dr Boyce).
The authors have indicated they have no financial relationships relevant to this article to disclose.
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PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics
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