South Korea not only has the greatest number of suicides among Organization for Economic Cooperation and Development (OECD) countries, but South Korea's suicide rate is increasing the fastest among OECD countries. The number of South Korean adolescents has decreased since 2000, the suicide rate of this population has been steadily increased, and suicide is currently the leading cause of death among South Korean adolescents (Chen et al., 2014; Jo et al., 2014). Therefore, to prevent suicide of Korean adolescents, it is important to investigate protective factors against of this problem.
Physical activity (PA) is proposed to be an effective prevention measure because it has been suggested to improve general physical and mental health (Brown et al., 2007). Apart from considerable physical health-related benefits, a number of psychological benefits have also been identified (Abell et al., 2009; Abu-Omar et al., 2004; Asztalost et al., 2008; Okano et al., 2003). For this reason, national health-promotion programs have recommended an increase of PA (Eaton et al., 2011; Kim et al., 2012). Physical activity levels are classified as vigorous, moderate, and low PA according to the Metabolic Equivalent of Task (MET) intensity levels (Ainsworth et al., 2011). Ainsworth et al. (2011) reported that one MET is considered a resting metabolic rate achieved during quiet sitting and PAs range from 0.9 (sleeping) to 18.0 METs (running at 10.9 mph). In addition, they also reported that the value of METs in terms of vigorous PA, moderate PA, and low PAs are 8.0, 6.0, and 3.3 METs, respectively. Currently, these PALs are applied to studies which calculate energy expenditure (Cho et al., 2011). The American College of Sports Medicine (ACSM) recommends that adolescents engage in 20 minutes of vigorous PA three days per week, 30 minutes of moderate PA at least five days per week, and 60 minutes of walking as a form of low PA at least five days per week (ACSM, 2010).
As South Korea experienced rapid economic development, its population underwent significant changes to western lifestyle. Due to these rapid changes to western lifestyle, the importance of increasing PA has been emphasized in adolescents and adults (Cho et al., 2011; 2014; Lee et al., 2012). Much of the current epidemiological evidence on the incidence and prevalence of suicidal ideation and suicidal behaviors is based on data from mainly high-income countries (Chen et al., 2014; Jo et al., 2014; Randall et al., 2014). These researchers have shown that psychosocial factors such as bullying, poverty, substance abuse and weak social relationships are associated with suicidal thoughts and behaviors. However, to the best of our knowledge, no studies to date have examined suicidal thoughts (ST) and suicidal attempts (SA) in relation to physical activity level in a nationally representative sample of Korean adolescents. Therefore, this study aimed to investigate whether the level of PA is associated with SA and ST in South Korean adolescents based on national data from the eighth Korea Youth Risk Behavior Web-based Survey (KYRBS VIII) in 2012.
Raw, cross-sectional data of the KYRBS- VIII in 2012 were used for this study. This dataset provides the basis for understanding the current level of health-risk behaviors in South Korean adolescents and can be used to calculate an adolescent health index for a health-promotion-project plan and evaluation. The KYRBS-VIII is an anonymous, self-administered online survey, which is officially approved by the Statistics Korea (Certificate Number: 11758). It is conducted annually by the Korea Center for Disease Control and Prevention (KCDCP). Details of the data-collection procedures are described by the KCDCP, and this survey has been shown to be valid and reliable (Bae et al., 2010). The study protocol was approved by the Korean Ministry of Health and Welfare in 2012 and was conducted in accordance with the Ethical Principles for Medical Research Involving Human Participants, as defined by the Helsinki Declaration. The KYRBS- VIII was administered to a nationally representative sample of middle- and high-school students, using a complex sampling design involving stratification, clustering and multistage sampling. A representative sample of students from grades 7-12, aged 13-18 was selected; this sample consisted of 78,255 student from 800 middle and high schools. From the selected schools, 74,186 students (38,221 boys and 35,965 girls) completed the questionnaire (response rate: 94.8%); all response were included in the data analysis.
The KYRBS- VIII consists of six questions regarding guidelines for vigorous, moderate, and low PA. The PA information was obtained in interviews using questions from the self-administered the International Physical Activity Questionnaire (IPAQ) (Craig et al., 2003). The vigorous, moderate, and low PA questions were about weekly frequency of 20 minutes of vigorous PA (e.g., soccer, basketball, aerobics, running, fast cycling, and fast swimming), 30 minutes of moderate PA (e.g., cycling at a regular pace, swimming at a regular pace, slow swimming, noncompetitive volley ball and doubles tennis), and 60 minutes of light PA (e.g., walking) in the past seven...