Sexual Intercourse and Its Correlates Among School-aged Adolescents in Indonesia: Analysis of the 2015 Global School-based Health Survey

Objectives This study aimed to determine the prevalence and correlates of sexual intercourse among junior secondary and high school students in Indonesia from the 2015 Global School-based Health Survey (GSHS). Methods The survey was conducted among 11 110 students from 75 schools in Indonesia using a self-administered questionnaire. Univariate and multivariate analyses were conducted to explore associations between sexual intercourse and socio-demographic variables, substance use, mental distress, and protective factors. Results Overall, 5.3% of students reported having ever had sex (6.9% of boys and 3.8% of girls). Of students who engaged in sexual intercourse, 72.7% of boys and 90.3% of girls had an early sexual debut (before reaching the age of 15) and around 60% had multiple sex partners. Sexual intercourse was associated with gender, school grade, smoking, alcohol consumption, drug use, suicidal ideation, truancy, peer support, and parental supervision. Conclusions These findings indicate a pressing need to develop more comprehensive sexual health education in the national curriculum. An effective strategy should also address other risky behaviours.


INTRODUCTION
Adolescence is a critical period in an individual's transition in health, social development, and well-being from childhood to adulthood. Adolescents make up 16% of the world's popula- pISSN 1975-8375 eISSN 2233 tion, and Asia is home to more than 600 million adolescents [1]. In 2016, Indonesia had 46 million adolescents, representing 18% of its total population [2]. As they cope with a range of health and social challenges as they navigate the pathway from childhood to adulthood, it is of the utmost importance for society to invest in them and to help them to thrive. Adolescents are also characterised by heightened impulsivity, which may lead to risky behaviour [3], such as early sexual intercourse. Adolescents often experience premarital sexual activity, which is significantly influenced by biological, psychological, and social factors [4]. Premarital sex is considered socially and culturally taboo in Indonesia. However, data from the 2017 Indonesia Demographic and Health Surveys indicated that around 4% of man adolescents aged 15-19 had sexual experience [5].
Premarital sexual activity among teenagers is mostly unsafe (i.e., without use of a condom), exposing them to various health problems, such as unwanted pregnancy, unsafe abortion, sexually transmitted diseases, and HIV/AIDS [4]. Furthermore, in Indonesia, limited access to targeted sexual and reproductive health (SRH) care and services for adolescents contributes to the high burden of SRH problems [6]. Between 2011 and 2015, new human immunodeficiency virus (HIV) infections in Indonesia increased annually by 13.1% among adolescents aged 15 to 19 [7]. In addition, approximately 8% of adolescents aged ≤19 years had experienced an unwanted pregnancy [8].
Although many scholars have studied the determinants of sexual intercourse among adolescents, limited information is available on the correlates of sexual intercourse among in-school adolescents in Indonesia. Previous studies have examined correlates of sexual behaviour in Indonesia, including self-esteem, psychological well-being, and social support [13,14]; however, these studies have been limited to few provinces (Jambi, Lampung, Jakarta, and Bali), and the appropriateness of this evidence to guide formulation of SRH policy and curriculum throughout Indonesia is implausible. Therefore, the findings of this study may help develop the most appropriate sexual health program and education for adolescents in Indonesia by using data from the 2015 Indonesia Global School-based Health Survey (GSHS).

Study Design
This study was based on a secondary analysis of the Indonesia GSHS conducted in 2015. The Indonesia GSHS used a twostage cluster sampling design to generate a representative sample of junior secondary (grade 7-9) and high school students (grade [10][11][12], who are typically aged 13-17 years. It is a part of collaborative survey between the US Centres for Disease Control (CDC), the World Health Organization, and the Ministry of Health of the Republic of Indonesia.

Sampling and Data Collection Procedure
At the first stage, the CDC selected a number of schools with probability proportional to school enrolment size. Seventyfive schools were selected from 68 districts in 26 provinces in Indonesia. At the next stage of sampling, classes in the selected schools were randomly selected and all students in the selected classes were eligible to participate irrespective of their actual age. The school response rate was 100%, while the student response rate was 94%. A total of 11 110 students participated in this study.
Data collection was taken place in selected schools under supervision of teachers and the research team. Students who did not attend school, were ill, or had difficulties responding to the questionnaire were excluded from the study. The participating students completed a self-administered GSHS standardised questionnaire that took on average 40 minutes to 50 minutes to complete on a computer-scannable answer sheet. They were also asked not to include their name or other identification code. The questionnaires were initially translated into Bahasa Indonesia prior to the study. At least 10 GSHS core questionnaire modules were used to collect demographic information from students, in addition to information on alcohol, tobacco, and drug use; sexual behaviours related to HIV/ AIDS; physical activity; violence/physical abuse; diet and nutrition; hygiene practices; truancy; perceived social support at school; and parental monitoring.

Study Variables
The variables used in this study are described in Table 1. The dependent variables were sexual intercourse, and the independent variables were socio-demographic characteristics (age, gender, grade), substance use (alcohol, tobacco, and drug use), mental distress (loneliness, anxiety, suicide), truancy, and protective factors (peer support and parental or guardian supervision).

Statistical Analysis
The data were coded and analysed using SAS Studio (SAS Institute Inc., Cary, NC, USA). The study adopted two ways of analysing of the data. At first, the proportions of sexual behaviour, socio-demographic characteristics, substance use, mental distress, and other protective factors were evaluated according to gender. Missing data were not estimated. Factors associated with sexual intercourse were also assessed using the Pearson chi-square test in the bivariate analysis. Any potential confounders and explanatory variables that were significant at the 0.25 level based on the Wald test were retained and entered into multivariate logistic regression models in the second step. In this step, the backward elimination method was used. The results from the regression analysis were presented as odds ratios (ORs) and adjusted ORs with their respective 95% confidence intervals (CIs). Sample weights were used to adjust for differences in the probability of selection between students.

Ethics Statement
The National Ethics Commission on Health Research, National Institute of Health Research and Development granted ethical approval for the 2015 Indonesia GSHS (LB.02.01/5.2/ KE.158/2015). Students were permitted to withdraw from the study at any time before or during data collection and could refuse to answer any questions. To maintain confidentiality, no personal identifiers were provided in the questionnaire and answer sheet. Table 2 presents the sample characteristics. Of the 11 110 participants included in the study, 54.2% were girls and 45.8% were boys. The majority of participants were junior secondary school students between grades 7 and 9 (76.8%) and around the age of 10-14 years (67.7%). Substance use was greater among boys than girls. The prevalence of current smoking and consumption of other tobacco products was 23.2% and 2.4%, respectively. The prevalence of current alcohol consumption was 7.3% among boys and 1.6% among girls, and that of lifetime illicit drug use was 3.3% among boys and 0.9% among girls, whilst mental distress was more likely to occur among girls than boys.

Sexual Behaviour and Associated Factors
The study found that 6.9% of boys and 3.8% of girls reported sexual intercourse in the past 12 months (Table 2). Furthermore, among those who engaged in sexual intercourse, 72.7% of boys and 90.3% of girls had their first sexual experience before reaching 15 years of age, and around 60% of sexually active boys and girls had more than 1 sexual partner ( Table 3). As is also shown in Table 3, more junior secondary students (5.8%) had sexual intercourse than high school students (3.7%).
Among students in grades 7-9 who had sexual experience, 94.5% had an early sexual debut (<15 years).
The results of the multiple logistic regression analysis are presented in Table 4. In the bivariate analysis, all variables were significantly associated with sexual intercourse among schoolaged children (p<0.05). However, after adjustment for sociodemographic, substance use, mental distress, and protective variables in the multivariate analysis, the variables that were associated with the outcome were men gender (OR, 1

DISCUSSION
This paper reports that more adolescent boys (6.9%) in Indonesia than girls (3.8%) had engaged in sexual intercourse. Similar findings were found in some previous GSHS studies [9][10][11]15]. The majority of both man and woman students who ever had sexual intercourse had their sexual debut before the age of 15 (90.3% for girls and 72.7% for boys). The lower debut  age among girls could be explained by the fact that girls tend to have an earlier onset of puberty than boys, and this is positively correlated with an early sexual debut [16]. These results, however, should be interpreted with caution since the majority (67.7%) of participants were under the age of 15 years. Our findings also found that more girls than boys reported having more than 1 sexual partner, which contradicts the findings of previous studies in the Pacific Islands and sub-Saharan Africa [9,11,15]. The risk of having multiple sexual partners among adolescent girls is known to be associated with several contextual factors, including family structure and household economic status, which were not investigated in the survey [17]. The current study further demonstrated that gender, school grade, substance use (tobacco, alcohol, and drugs), suicidal ideation, school truancy, peer support, and parental supervision were associated with sexual intercourse in the past 12 months. Boys were more likely to have engaged in sexual intercourse than girls. It has been argued that boys and girls have different experiences of puberty and sexual behaviours [18]. Boys are more likely to have positive expectations about sex, whilst girls seem to have emotional reasons for having sex, which are mostly related to other needs such as the need for love, self-esteem, and self-ascertainment [19].
These differences are not merely due to different psychological or biological characteristics of boys and girls. Previous literature suggests that race, ethnicity, and sexual preference also shape adolescents' experiences of puberty and first sexual debut [18]. In addition, sociocultural and environmental factors, such as family upbringing, have a strong influence on adolescents' perceptions of sexuality and their sexual behaviour [20]. Physical and biological changes during puberty make boys look older, more masculine, and more independent to parents; thus, boys are granted more recognition of their selves. For girls, looking older means looking more sexual, to which parents often respond by implementing greater restrictions, rather than by enabling greater independence [18].
Substance use (tobacco, drugs, and alcohol) was associated with an increased likelihood of sexual intercourse in this study. Similar findings were reported in the previous GSHS studies in the Pacific Islands, Brunei Darussalam, and Namibia [9,11,12]. The majority of teenagers reporting early sexual behaviour also reported using alcohol and drugs before sex [21,22]. Alcohol alone has been reported to increase the desire to have sex and to initiate or participate in sex [22][23][24]. The use of intravenous drugs or other illicit substances has also been reported to increase cognitive inhibition [25] and poor behavioural judgment [26]. Several illicit drugs, such as opium, produce intense feelings of pleasure, which could directly stimulate feelings of sexual desire and pleasure [24].
Current smoking was also significantly associated with early sexual debut among school-aged adolescents. Recent evidence suggests that individuals who initiate smoking at a relatively early age tend to engage in unprotected sex under the influence of alcohol or drugs [27]. Although the causal nature of this relationship remains unclear [28], it is important to point out that adolescents who reported having ever smoked were identified as much more likely to engage in sexual intercourse. In Indonesia, people start smoking at a relatively young age. The 2014 Global Youth Tobacco Survey found that of 43.2% of students who have ever smoked a cigarette reported that they started smoking at 12-13 years of age [29]. Therefore it is necessary to implement smoking behaviour control strategies through health education on the dangers of smoking that starts at a very young age, although such policies are apparently insufficient to curb the rate of smoking, especially among teenagers [30].
Another distinctive finding of this study was the positive association between suicidal ideation and sexual intercourse. Although this result is consistent with previous studies among school-going adolescents [11], the nature of the relationship remains unclear. A study in Sweden found that perceived poorer health and mental well-being was more prominent among girls with early sexual debut (at the age of 14 or younger). The increased probability of sexual intercourse in relation to poor mental health among adolescents could be explained based on proposals made in several studies [11]. For instance, the concept of self-efficacy in Bandura's social cognitive theory suggests that people who are depressed have less capacity to take control over their lives, including areas pertaining to sexual behaviour [11,31]. Hence, adolescents who have higher sexual self-efficacy may exhibit less risky sexual behaviour.
Regarding protective factors, our study found that having close friends and/or parental or guardian supervision decreased the likelihood of adolescents being sexually active, which is consistent with previous GSHS study findings [9,32]. The social environment provides meaningful relationships, encourages self-expression, and provides structure that may help prevent adolescents from initiating sex at a young age [18]. Parents are known to be health-promoting socialisation agents for information about norms and behaviours, who are likely to encour-age their children to delay the onset of sexual intercourse [33]. Parents and schools may have positive impacts on adolescent's sexual cognition to postpone sexual intercourse, while peers and mass media provide information that might accelerate adolescents' sexual activity [34]. Peer relationships have the potential to promote risky sexual behaviour, as peers are a source of emotional support among teenagers [35].
In an effort to delay the initiation of sexual intercourse and prevent sexually transmitted infections, school-aged adolescents should be provided with sexual health education and be encouraged through positive attitudes regarding gender and adolescent reproductive health (ARH) norms during puberty based on the social and cultural context of Indonesia. Since sexuality remains a taboo and sensitive subject in many areas of Indonesia, it is rarely discussed by adolescents explicitly with their parents [36]. This leads parents to be a bit conservative when explaining information related to sexuality to their children. Similar to parents, school teachers often neglect that teaching students about sexuality must be done with a gender-neutral approach. Indeed, ARH is only addressed to a limited degree [37].
Culturally appropriate and evidence-based education on sexuality and ARH is therefore important to help adolescents be well-informed about healthy relationships and take responsibility for their SRH. To date, the implementation of ARH education in schools has been associated with health movements in schools (Usaha Kesehatan Sekolah) through counselling, periodic health check-ups, and immunisations [38]. It is encouraging to equip the curriculum with the topic of sex education, with the aim of enabling students to obtain accurate information for developing their own personal attitudes related to sexuality. In addition, school-based strategies should also address other risky behaviours, such as smoking and other substance use.

Strengths and limitations
There are several limitations to this study. As adolescents who did not attend school were not included, the findings may not be representative of all adolescents. Also, as the survey was cross-sectional, no causal interpretations can be made. The survey used in this study relies mainly on self-reports of sexual behaviour, some of which may be misreported due to shame and taboo concerning early sexual debut. We also used proxy measures for depression, anxiety, and suicide, which are quite limited in their use as quantitative measures of mental health.
Nevertheless, this study may contribute to the following: (1) the identification of the correlations of sexual behaviour with smoking, alcohol consumption, suicide, and truancy among students in Indonesia; (2) the development of specific insights on understanding unhealthy behaviours among adolescents in the Indonesian context, which may require further action by the authorities for both education and health sectors; (3) the provision of recommendation on strategies to address risky behaviours among adolescents in Indonesia.
Our study found a low prevalence of sexual intercourse among in-school adolescents in Indonesia. The factors associated with sexual activity were gender, school grade, substance use (tobacco, alcohol, and drugs), suicidal ideation, school truancy, peer support, and parental supervision. Our findings suggest that there is an urgent need to review the current school health policies and curriculum. Strategies for changing unhealthy behaviours strategies should include educational programs on school-based comprehensive sexual reproductive health and substance use control. Further research is also needed to examine the social patterns and determinants of engagement in adolescent sexual behaviours. This would provide more insights for points that ARH programs should be emphasised in the context of students in Indonesia.
who have given generously of their time and participation to the study.