Abstract

Introduction

In 2009, the World Health Organization (WHO)* reported that there were approximately 33.3 million people living with the Human Immunodeficiency Syndrome (HIV) worldwide, of which 2.6 million were new infections and, of these, nearly 370,000 occurred in individuals younger than 15 years. In Brazil, it is estimated that 630,000 people are infected**. In recent years, the portion of the Brazilian population who has received more diagnoses of HIV is comprised of adolescents, women (especially between 13 and 19 years), and individuals with a low socioeconomic status and level of education***.

Protection during sexual intercourse continues to be the most efficient method against this infection. Two homonymous research projects entitled “ Pesquisa sobre Conhecimentos, Atitudes e Práticas relacionada às DST e AIDS ” (PCAP – Survey of Knowledge, Behavior and Practices Associated with STDs and AIDS), conducted in 2004 and 2008, interviewed individuals aged 15-64 years of all Brazilian regions and showed that 96.6% of them were aware that condoms prevented sexually transmitted diseases (STD) and the Acquired Immunodeficiency Syndrome (AIDS)****. Knowledge was assessed according to questions about healthy appearance, partner's fidelity, use of condoms, sharing needles and cure of AIDS. According to data from 2008, adolescents who reported having more sexual partners in general had high knowledge about how to prevent STDs and mentioned a more frequent use of condoms, compared to other age groups. This last result was similar to that found by Paiva et al. (2008)¹1. Paiva V, Calazans G, Venturi G, Dias R. Idade e uso de preservativo na iniciação sexual de adolescentes brasileiros. Rev Saude Publica 2008; 42(S1): 45-53., who also assessed national data from the study entitled “ Comportamento Sexual e Percepções da População Brasileira Sobre HIV/Aids ” (Sexual Behavior and Perceptions of HIV/AIDS among the Brazilian Population), conducted between 1998 and 2005. However, when comparing the results of the latter study* from 1998 with the 2008 PCAP information about the use of male condoms in the first sexual intercourse in adolescents aged 15-24 years, the prevalence of such use increased from 52.8% to 60.9%, thus showing that this practice is still low among adolescents**. Likewise, although the 2004 and 2008 PCAP studies revealed behavioral changes, the use of condoms was low in these two years for both “last sexual intercourse in the previous 12 months” (<40%) and “all sexual relations with any partner in the previous 12 months” (<30%). Thus, the results of these studies indicate that a higher level of knowledge about STDs and AIDS in the Brazilian population does not necessarily translate into safe sexual practices.

Another important aspect is that little is known about how younger individuals understand this disease, especially those aged less than 15 years, who are beginning their sexual life¹1. Paiva V, Calazans G, Venturi G, Dias R. Idade e uso de preservativo na iniciação sexual de adolescentes brasileiros. Rev Saude Publica 2008; 42(S1): 45-53.. The majority of studies on this theme have been conducted in adolescents older than 15 years of age, among which STD and AIDS knowledge varies from average to very good²2. Martins LB, da Costa-Paiva LH, Osis MJ, de Sousa MH, Pinto-Neto AM, Tadini V. Fatores associados ao uso de preservativo masculino e ao conhecimento sobre DST/AIDS em adolescentes de escolas públicas e privadas do Município de São Paulo, Brasil. Cad Saúde Pública 2006; 22(2): 315-23.

3. Romero KT, Medeiros EH, Vitalle MS, Wehba J. O conhecimento das adolescentes sobre questões relacionadas ao sexo. Rev Assoc Med Bras 2007; 53(1): 14-9. ^{- 4}4. Sikand A, Fisher M, Friedman SB. AIDS knowledge, concerns, and behavioral changes among inner-city high school students. J Adolesc Health 1996; 18(5): 325-8..

Inappropriate knowledge about HIV/AIDS can lead to practices that affect the health of adolescents⁵. For this reason, the availability and quality of information before sexual initiation must be investigated¹1. Paiva V, Calazans G, Venturi G, Dias R. Idade e uso de preservativo na iniciação sexual de adolescentes brasileiros. Rev Saude Publica 2008; 42(S1): 45-53.. Considering the early age of beginning of sexual intercourse – before the age of 15 years in the majority of cases, regardless of gender – it is essential to identify the factors associated with knowledge about HIV/AIDS transmission since the beginning of adolescence, because they can contribute to public policies aimed at reducing the advance of HIV infections⁶.

Thus, the present study aimed to analyze the effect of demographic and socioeconomic factors and sexual education received at school and at home on the level of knowledge about HIV/AIDS transmission in a sample of adolescents aged 11 years of age living in Southern Brazil.

Methods

Research participants were part of a prospective cohort study in which hospital births that occurred in the city of Pelotas in 1993 were monitored (N=5,249). At the time of birth, a questionnaire was applied to mothers to obtain information about socioeconomic and demographic conditions, pregnancy and delivery, and newborns were weighed and measured⁷7. Victora CG, Araujo CL, Menezes AM, Hallal PC, Vieira Mde F, Neutzling MB et al. Methodological aspects of the 1993 Pelotas (Brazil) Birth Cohort Study. Rev Saúde Pública 2006; 40(1): 39-46.. In 2004-5, when adolescents were 11 years of age (mean=11.3±0.3), all cohort participants were sought for a new follow-up to investigate general health and socio-demographic conditions, family and social relationships, adolescent habits and knowledge about HIV/AIDS transmission, and a response rate of 87.5% was achieved. Knowledge about HIV/AIDS was assessed with a confidential questionnaire, completed by the adolescent exclusively, where there were five questions about this theme, to which the responses should be “yes” or “no”. The questions in this instrument were as follows: “Do you think one can get AIDS…” 1) “by sharing a syringe with another person?”; 2) “when a man has sex with a woman?”; 3) “when a man has sex with another man?”; 4) “by open-mouth kissing?”; 5) “by hugging someone with AIDS?”. The three first questions were included considering the main forms of HIV/AIDS transmission, whereas the other two referred to situations that could lead to discrimination against HIV-positive individuals and were selected from questionnaires used in other Brazilian studies that also investigated adolescents²2. Martins LB, da Costa-Paiva LH, Osis MJ, de Sousa MH, Pinto-Neto AM, Tadini V. Fatores associados ao uso de preservativo masculino e ao conhecimento sobre DST/AIDS em adolescentes de escolas públicas e privadas do Município de São Paulo, Brasil. Cad Saúde Pública 2006; 22(2): 315-23.

3. Romero KT, Medeiros EH, Vitalle MS, Wehba J. O conhecimento das adolescentes sobre questões relacionadas ao sexo. Rev Assoc Med Bras 2007; 53(1): 14-9.-⁴4. Sikand A, Fisher M, Friedman SB. AIDS knowledge, concerns, and behavioral changes among inner-city high school students. J Adolesc Health 1996; 18(5): 325-8., ***.

Aiming to investigate the factors associated with knowledge about HIV/AIDS, adolescents' demographic, socioeconomic and sexual education characteristics were analyzed. The independent variables included in this study were as follows: sex (male/female); self-reported ethnicity (white, mixed, black); maternal level of education in years of school completed (0-4, 5-8, 9-11, ≥12); economic class analyzed with the assets index⁸(tertiles); type of school attended (municipal/state/private); whether the adolescent had ever had any sexual education classes (yes/no); and whether the father and/or mother had ever talked about sex with them (yes/no). Questions about sexual education were also included in the confidential questionnaire applied to adolescents. The remaining information was collected by interviewers who had been properly trained for this study, using a general questionnaire applied to the mothers that included questions about general health and socio-demographic questions. The “assets index” variable was constructed from the main component analysis, which considered the ownership of several household goods and characteristics. Only the first main component analysis factor was used to create this variable, as it explained 30% of the variance of the model. This factor was subsequently divided into tertiles (categorized in an increasing order where the 1^sttertile included individuals with the lowest socioeconomic level) for the purposes of the analysis⁹9. Araujo CL, Menezes AM, Vieira M de F, Neutzling MB, Goncalves H, Anselmi L et al. The 11-year follow-up of the 1993 Pelotas (Brazil) birth cohort study: methods. Cad Saúde Pública 2010; 26(10): 1875-86..

With regard to data analysis, each of the five questions about HIV/AIDS was considered as a different outcome. The following wrong responses to the five questions about forms of HIV/AIDS transmission were taken into consideration for the analyses: negative responses to the three situations in which one may be infected with HIV/AIDS (heterosexual intercourse, homosexual intercourse and sharing syringes) and affirmative responses to the two situations which involve no risk (hugging someone with HIV and open-mouth kissing). Blank responses were considered as ignored values. The chi-square test was used in the crude analysis to compare the prevalences of “wrong” responses to each question about HIV/AIDS knowledge. Poisson regression with robust variance adjustment¹⁰10. Barros AJ, Hirakata VN. Alternatives for logistic regression in cross-sectional studies: an empirical comparison of models that directly estimate the prevalence ratio. BMC Med Res Methodol 2003; 3: 21.was used in the adjusted analysis. In addition, adjusted prevalences were estimated for each category of independent variables, using the margins command of Stata software. A conceptual model that makes the adjustment for possible confounding factors was developed for the multivariate analysis. In this model, variables are controlled for those on the same level or on higher levels¹¹11. Victora CG, Huttly SR, Fuchs SC, Olinto MT. The role of conceptual frameworks in epidemiological analysis: a hierarchical approach. Int J Epidemiol 1997; 26(1): 224-7.. On the first level are the socio-demographic variables (sex, ethnicity, maternal level of education and assets index) and on the second level are the type of school and sexual education variables (received from the parents and school). A p-value<0.20¹²12. Maldonado G, Greenland S. Simulation study of confounder-selection strategies. Am J Epidemiol 1993; 138(11): 923-36.was used as the cut-off point to maintain the variables in the multivariate model. A statistical significance level of 5% was adopted for two-tailed tests and analyses were performed in the Stata software, version 11.0¹³13. StataCorp. Stata Statistical Software: Release 9. Texas: Stata Corporation LP; 2005..

The present study was approved by the Universidade Federal de Pelotas Medical School Research Ethics Committee. Parents or responsible adults authorized the participation of adolescents in this study.

Results

Of all 4,452 adolescents interviewed, information about the five outcomes considered was obtained from 3,949 of them, totaling 11.3% of losses for one or more questions about HIV/AIDS transmission. The response rate was higher among adolescents whose mothers had 12 years of school or more, with a higher socioeconomic level, who studied in private schools, and who had already received information about sex from their father, mother or school ( Table 1 ). There were no differences according to sex or ethnicity. Half of the respondents were females, two thirds reported they were white, one fourth had mothers with less than five years of school and 11% studied in private schools. In 20% and 30% of cases, the father and mother, respectively, had already talked with adolescents about sex, and 45% had had sexual education classes at school. With regard to sexual education at home, mothers had more contact with girls, whereas fathers had more contact with boys ( Figure 1 ).

The information received at school was similar in both sexes. The percentages of wrong knowledge about the three situations in which HIV/AIDS can be acquired were 17.2% (95%CI 16.0-18.3) for heterosexual intercourse, 44.1% (95%CI 42.6-45.7) for homosexual intercourse, and 34.9% (95%CI 33.5-36.4) for sharing syringes. Of all participants, only 41% responded these three questions correctly, 17% responded two questions incorrectly and 10% responded all questions incorrectly ( Figure 2 A). With regard to open-mouth kissing, 25.6% of adolescents (95%CI 24.3-27.0) responded the question incorrectly, whereas 16.2% (95%CI 15.1-17.4) answered that HIV can be transmitted when hugging someone with HIV/AIDS. Only 64% of participants responded both questions correctly, while 6% answered them incorrectly ( Figure 2 B).

Table 2 shows the percentages of wrong responses to the three situations in which HIV/AIDS may be transmitted. The factors associated (and the direction of the associations) with the “heterosexual intercourse” and “sharing syringes” outcomes were the same in the crude analysis: higher percentage of errors among boys, mixed and black adolescents, those with a lower maternal level of education and socioeconomic level, those studying in public schools (municipal and state) and those who had not received sexual education at school or home. In the adjusted analysis, ethnicity, type of school and sexual education received from parents lost association with the two outcomes in the adjusted analysis; the assets index remained inversely associated with wrong knowledge about heterosexual intercourse exclusively. With regard to HIV/AIDS infection through homosexual intercourse, the percentage of error in the crude analysis was higher among girls, those who had not had sexual education classes and those whose father or mother had not talked about sex with them. In the adjusted analysis, only sex, sexual education received at school and mother who had talked about sex with adolescent remained associated with this outcome.

Table 3 shows the crude and adjusted prevalences of wrong responses to the two situations in which HIV/AIDS cannot be transmitted. In the crude analysis, wrong knowledge about HIV/AIDS transmission through “open-mouth kissing” was only associated with maternal level of education and assets index, with an inverse trend in both cases. After adjustment for confounding factors, the association with maternal level of education remained practically the same, whereas the assets index lost its strength of association and statistical significance. When the “hugging someone with HIV/AIDS” outcome is considered, the percentage of wrong responses was higher among boys, those with a lower maternal level of education and socioeconomic level, those studying in public schools and those who had already had sexual education at school or talked about sex with any of their parents. In the adjusted analysis, only maternal level of education, assets index (both with an inverse relation) and sexual education received by the mother remained associated.

Discussion

There are many controversies about the weight of knowledge on sexual behavior prevention¹⁴14. DiClemente RJ, Durbin M, Siegel D, Krasnovsky F, Lazarus N, Comacho T. Determinants of condom use among junior high school students in a minority, inner-city school district. Pediatrics 1992; 89(2): 197-202. ^{, 15}15. Ku L, Sonenstein FL, Lindberg LD, Bradner CH, Boggess S, Pleck JH. Understanding changes in sexual activity among young metropolitan men: 1979-1995. Fam Plann Perspect 1998; 30(6): 256-62.. Several studies point out that knowledge does not guarantee continuing prevention in all sexual relations¹⁶16. Doreto DT, Vieira EM. O conhecimento sobre doenças sexualmente transmissíveis entre adolescentes de baixa renda em Ribeirão Preto, São Paulo, Brasil. Cad Saúde Pública 2007; 23(10): 2511-6. ^{, 17}17. Trajman A, Belo MT, Teixeira EG, Dantas VC, Salomao FM, Cunha AJ. Knowledge about STD/AIDS and sexual behavior among high school students in Rio de Janeiro, Brazil. Cad Saúde Pública 2003; 19(1):127-33.. In Brazil, seeking to include the largest number of adolescents possible, health and education policies were developed, in which schools, family members and health professionals are encouraged to raise the issue of STD prevention and adolescent pregnancy with this population. However, knowledge about this theme has been assessed and found not to be consistently sufficient for prevention in all sexual relations, as observed in several studies²2. Martins LB, da Costa-Paiva LH, Osis MJ, de Sousa MH, Pinto-Neto AM, Tadini V. Fatores associados ao uso de preservativo masculino e ao conhecimento sobre DST/AIDS em adolescentes de escolas públicas e privadas do Município de São Paulo, Brasil. Cad Saúde Pública 2006; 22(2): 315-23.

3. Romero KT, Medeiros EH, Vitalle MS, Wehba J. O conhecimento das adolescentes sobre questões relacionadas ao sexo. Rev Assoc Med Bras 2007; 53(1): 14-9.-⁴4. Sikand A, Fisher M, Friedman SB. AIDS knowledge, concerns, and behavioral changes among inner-city high school students. J Adolesc Health 1996; 18(5): 325-8.. Nevertheless, effective education about HIV/AIDS with adolescents who are not sexually active or who are much younger (<14-15 years) has not been assessed¹⁸18. Piot P, Bartos M, Larson H, Zewdie D, Mane P. Coming to terms with complexity: a call to action for HIV prevention. Lancet 2008; 372(9641): 845-59. This study obtained important results about the theme of adolescents aged 11 years from a population-based study by observing the influence of several demographic, socioeconomic and educational factors on knowledge about HIV/AIDS transmission among adolescents of an average-size city in Southern Brazil.

One of the findings that should be emphasized is who the adolescents with a lower level of knowledge about HIV/AIDS transmission are. They belong to families with a lower level of education and socioeconomic level. Probably, the more limited access to appropriate sources of information (such as books, magazines and newspapers) could partly explain the findings of this study. Similar results have been reported by other authors who worked with wider age groups, usually between 13 and 24 years²2. Martins LB, da Costa-Paiva LH, Osis MJ, de Sousa MH, Pinto-Neto AM, Tadini V. Fatores associados ao uso de preservativo masculino e ao conhecimento sobre DST/AIDS em adolescentes de escolas públicas e privadas do Município de São Paulo, Brasil. Cad Saúde Pública 2006; 22(2): 315-23. ^{, 3}3. Romero KT, Medeiros EH, Vitalle MS, Wehba J. O conhecimento das adolescentes sobre questões relacionadas ao sexo. Rev Assoc Med Bras 2007; 53(1): 14-9. ^{, 17}17. Trajman A, Belo MT, Teixeira EG, Dantas VC, Salomao FM, Cunha AJ. Knowledge about STD/AIDS and sexual behavior among high school students in Rio de Janeiro, Brazil. Cad Saúde Pública 2003; 19(1):127-33., using questions about HIV/AIDS transmission knowledge similar to those of the present study. However, it should be emphasized that adolescents' understanding of certain questions, such as HIV transmission through sharing syringes, may have been influenced by the younger age of participants in this study. Nevertheless, the associations found for this form of transmission were consistent with the findings for infection through heterosexual and homosexual intercourse, thus suggesting that this limitation did not affect the results. Another possible limitation of this study, which could have somewhat interfered with the findings, is associated with the rate of non-respondents. However, the percentage of non-respondents was significantly higher among adolescents with a lower maternal level of education and socioeconomic level, which could be associated with a lower level of knowledge about this theme. Thus, the associations found here have probably been underestimated and, consequently, the measures of the effect must be even higher.

Another important fact refers to the source of sexual education received by adolescents. Talking about sex with the mother was consistently associated with adequate knowledge about forms of HIV/AIDS transmission, whereas the influence of paternal sex education was not associated with any of the outcomes in the adjusted analysis. It should be emphasized that only the information about “open-mouth kissing” showed no association with “talking about sex with the mother”. Mothers seem to be more open to intimate conversations, creating an important family environment for issues such as adolescence, sexuality and DSTs, as observed in a recent systematic review¹⁹19. Commendador KA. Parental influences on adolescent decision making and contraceptive use. Pediatr Nurs 2010; 36(3):147-56, 70.. Many studies have already shown how maternal care since birth can influence the health of a child. In addition, mothers are culturally responsible for feeding, hygiene and socialization²⁰20. Victora CG, Adair L, Fall C, Hallal PC, Martorell R, Richter L, et al. Maternal and child undernutrition: consequences for adult health and human capital. Lancet 2008; 371(9609): 340-57.. The educational role of mothers has been maintained and reconstructed for years and their role in this process continues to be essential, despite the growing number of women present in the job market (with subsequent less time to spend at home)²¹21. IPEA. Retrato das desigualdades de gênero e raça . Brazília: Instituto de Pesquisa Econômica Aplicada; 2008.. For this reason, the educational role of mothers in HIV/AIDS prevention must be emphasized and taken into consideration in public health education policies aimed at reducing this disease. Parents should not be ignored in these policies, as their messages could raise knowledge about this issue and related practices¹⁹19. Commendador KA. Parental influences on adolescent decision making and contraceptive use. Pediatr Nurs 2010; 36(3):147-56, 70.>.

The results of the present study are in agreement with other studies conducted in large cities of Brazil. A study performed with adolescents aged 15-19 years, living in an area of the city of São Paulo covered by a family health unit, revealed that the mother is the person who provides knowledge about these issues, especially in the case of girls, when parents are chosen as the main source of such knowledge²²22. Borges ALV, Nichiata LYI, Schor N. Conversando sobre sexo: a rede sociofamiliar como base de promoção da saúde sexual e reprodutiva de adolescentes. Rev Latino-Am Enfermagem 2006; 14(3): 422-7.. According to the authors, the low participation of parents in these conversations and in the family prevents them from transmitting knowledge about issues considered to be more intimate and delicate by adolescents. However, parents were the most frequently mentioned source of knowledge in a study conducted by Romero et al.³3. Romero KT, Medeiros EH, Vitalle MS, Wehba J. O conhecimento das adolescentes sobre questões relacionadas ao sexo. Rev Assoc Med Bras 2007; 53(1): 14-9.. Nevertheless, these authors pointed out that, if conversations with adolescents are superficial, there will not be adequate explanation about the need for care prior to beginning one's sexual life and being aware of STD prevention.

In addition, two results refer to the lower level of knowledge by sex and that of adolescents who reported they were black and mixed. Girls reported a higher level of knowledge about almost all the questions asked, with the exception of HIV transmission through male-male homosexual intercourse, to which boys had more correct responses. However, the fact that girls knew more about the topics investigated cannot be a guarantee of the care required for all sexual relations. The literature consistently refers to the reduction in the use of condoms between the first and last sexual intercourse and points out that the decision to use condoms, essential to prevent HIV/AIDS, is influenced by socio-cultural, contextual and individual factors²³23. Béria J. Ficar, transar: a sexualidade do adolescente em tempos de AIDS . Porto Alegre: Tomo; 1998..

The associations found for HIV/AIDS knowledge and adolescent ethnicity lost their significance after the adjustment for socioeconomic level, suggesting that maternal level of education and family socioeconomic conditions determine adolescents' level of knowledge. However, even after the adjustment, the percentage of inadequate knowledge about heterosexual intercourse, open-mouth kissing and hugging someone with HIV/AIDS was higher among black participants, with borderline statistical associations. This is consistent with the study conducted by Ferreira et al. (2008), who analyzed knowledge about HIV/AIDS among adolescents and adults aged between 16 and 65 years in Brazil, in 1998 and 2005²⁴. The same finding, a lower level of knowledge about HIV/AIDS among those who reported they were black, was also described by Martins et al.²in the city of São Paulo and by Trajman et al.¹⁷in the city of Rio de Janeiro.

Finally, with regard to the type of school where adolescents studied, those in private schools showed a higher level of knowledge in the crude analysis, although associations were not consistently found after adjustment, which suggests that the level of knowledge does not depend on the type of school, but rather on whether adolescents have sexual education classes. School classes were particularly found to be a protective factor for questions in which HIV/AIDS infection was possible, but they were not associated with knowledge about infection through open-mouth kissing or hugging someone with HIV/AIDS. This fact shows that the teaching and the information being transmitted at school should be further investigated and worked on in educational institutions and taken into consideration by public health policies. Information about STDs is available to public and private primary schools students, starting in the 4^thor 5^thgrade, which coincides with the beginning of affective-sexual interests and practices. In these situations, there are several factors involved with prevention messages, causing the relation among information, knowledge, behavior and health to be much more complex, such as the nature of the questions, the teacher's/health professional's performance, the relationship among students and between students and teacher/health professional²⁵. Additionally, it is essential that adults and parents receive information about how to guide their children, so that knowledge can be translated into practices that are less vulnerable to STDs. Apart from these considerations, the need to understand how knowledge can be turned into preventive actions should be emphasized, in addition to assessing such knowledge. For this reason, new studies are required to deepen the knowledge about what the forms of education are (in the broadest sense) and how they can reduce adolescents' vulnerability to STDs, especially among those aged less than 15 years.

Authors' contributions: H Gonçalves, DA González and SC Dumith participated in all stages of the study. AMB Menezes, PC Hallal and CLP Araújo coordinated the study and approved the final version of the manuscript.

Acknowledgements: The analyses performed in this study were supported by the Wellcome Trust (Process 072 403/Z/03/Z). The previous stages were supported by the European Union, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq – National Council for Scientific and Technological Development) and Fundação de Amparo à Pesquisa do Rio Grande do Sul (FAPERGS – State of Rio Grande do Sul Research Support Foundation), Programa Nacional de Núcleos de Excelência (PRONEX/CNPq – National Program of Excellence Centers) and Brazilian Ministry of Health.

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