Early Sexual Initiation among Young Bahamian and its Implications for HIV Prevention

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Early Sexual Initiation among Young Bahamian and its Implications for HIV Prevention
 

– Reported, February 11, 2012

 

Behavioral research and prevention intervention science efforts have largely been based on hypotheses of linear or rational behavior change. Additional advances in the field may result from the integration of quantum behavior change and catastrophe models. Longitudinal data from a randomized trial for 1241 pre-adolescents 9–12 years old who self-described as virgin were analyzed. Data for 469 virgins in the control group were included for linear and cusp catastrophe models to describe sexual initiation; data for the rest in the intervention group were added for program effect assessment. Self-reported likelihood to have sex was positively associated with actual initiation of sex (OR=1.72, 95% CI: 1.43–2.06, R2 = 0.13). Receipt of a behavioral prevention intervention based on a cognitive model prevented 15.6% (33.0% vs. 48.6%, OR = 0.52, 95% CI: 0.24–1.11) of the participants from initiating sex among only those who reported “very likely to have sex.” The beta coefficients for the cubic term of the cusp assessing three bifurcating variables (planning to have sex, intrinsic rewards from sex and self-efficacy for abstinence) were 0.0726, 0.1116 and 0.1069 respectively; R2 varied from 0.49 to 0.54 (p<0.001 for all). Although an intervention based on a model of continuous behavior change did produce a modest impact on sexual initiation, quantum change has contributed more than continuous change in describing sexual initiation among young adolescents, suggesting the need for quantum change and chaotic models to advance behavioral prevention of HIV/AIDS

Sexual initiation (defined as the first engagement in anal or vaginal sexual intercourse in an individual’s life) is a critical event in the development of healthy and/or risky sexual behavior. Younger age at the time of sexual initiation has been recognized as a significant predictor of consequent sexual behaviors leading to increased risk of HIV infection . Understanding the process of sexual initiation is therefore essential for HIV prevention. The process of sexual initiation among adolescents may contain both rational and catastrophic components.

To conduct the intervention trial, 1360 participants in 15 of the total 26 government schools from New Providence of The Bahamas were randomly assigned to a control group (5 schools, N= 497) and two intervention groups (10 schools, N=863). The participants were predominantly African descents, 53% girls, and aged 9–12 years when entering the trial. Youth in the control group received an environmental/ecology intervention (the parents received a career planning intervention); youth in the two intervention groups received an HIV risk reduction intervention (the parents received either the career planning intervention or a parental monitoring intervention). To assess sexual initiation, we included only participants who were self-described as virgin (N=1241) upon entering the study, the 469 in the control group were used for modeling sexual initiation and the 772 in the intervention group were used for program effect evaluation. Data were collected using questionnaires in classrooms at the baseline and every 6 months through the 24 months follow-up.

Sexual initiation was the dependent variable for both the CBC-based and the QBC-based modeling. We defined sexual initiation as the first time an adolescent virgin was involved in sexual intercourse (including vaginal and anal sex). In the baseline and all follow-up surveys, the participants were asked two questions: “Have you ever had sex that is when a boy or man put his penis into a girl’s vagina?” (Yes/no) and “Have you had anal sex, where a man or a boy put his penis in a boy’s or girl’s anus or butt?” (Yes/no). A participant was considered as having initiated sex if he or she responded negatively to both questions in prior waves of the survey and responded positively for the first time to either of two questions in the subsequent survey.
Three Bifurcation Variables for Catastrophe Modeling
Planning for sex
This variable was assessed according to the self-reported likelihood of having sex in the next 6 months. In each wave of data collection, all participants including those who reported never having had sex were asked “How likely is it that you will have sex in the next 6 months”? A five-point Likert scale was used to assess responses to this question varying from “very unlikely” (coded as 1), to “unlikely” (coded as 2), “don’t know/not sure” (coded as 3, “likely” (coded as 4) and “very likely” (coded as 5).

Intrinsic rewards from sex
This variable was assessed using the question, “How would you feel if you were to have sex in the next six months?” Answer options to this question included “Very bad” (coded as 1), “Somewhat bad” (coded as 2), “Neither good nor bad” (coded as 3), “Good” (coded as 4) and “Very good” (coded as 5).
Self-efficacy regarding abstinence
This variable was assessed based on the responses (varying from “Strongly agree” to “Strongly disagree” and coded as 1 to 5) of participants to the following three statements (Cronbach a = 0.87): (a) “Even if all my friends were having sex, I would not feel I would have to have sex”; (b) “I would be able to say no to someone I am going with if I didn’t want to have sex” and (c) “I could go with a person for a long time and not have sex with him/her.” The average score of the three items was computed and used for analysis.

Sexual Progression Index
To conduct QBC-based catastrophe modeling, we used a four-level sex progression index (SPI). SPI was defined using self-reported data regarding ever having had sexual intercourse and the perceived likelihood of having sex in the next 6 months. SPI was set to “1” for participants who reported never having had sexual intercourse and who indicated no possibilities they would have sex in the next six months (e.g., responded “very unlikely” to the question “how likely is it you will have sex in the next 6 months”); SPI was set to “2” for participants who reported never having had sex but who were unsure if they were going to have sex in the next 6 months (e.g., responded “likely,” “neutral,” and “unlikely”); SPI was set to “3” for participants who never had sex and claimed that they were going to have sex in the next 6 months (e.g., responded “very likely”); and lastly SPI was set to “4” for participants who initiated sexual intercourse regardless of their planning to have sex in the future.
Incidence Kate of Sexual Initiation
Rate of sexual initiation was estimated using the incidence rate method. The five waves of data collection from the baseline through the 24 months follow-up created four periods for assessing sexual initiation: (a) from the baseline to the first follow-up at six months post intervention, (b) from the first follow-up to the second follow-up at 12 months post intervention, (c) from the second follow-up to the third follow-up at 18 months post intervention, and (d) from the third follow-up to the fourth follow-up at 24 months post intervention. To compute the incidence rate, we counted and summed the number of participants who initiated sex during each of the four periods as the numerator. We then counted and summed the numbers of virgins at the beginning of each of the four periods as the denominator. The six-month incidence rate was thus computed as the ratio of the two. Since each of the four follow-up intervals covered only six months, we then estimated the annual incidence rate of sexual initiation by converting the six-month basis into person-years at risk for sexual initiation as the denominator to estimate the initiation rate.

CBC-Based Statistical Analysis
To test the CBC-based hypothesis that sexual initiation is a rational choice made by young adolescents, we first compared the incidence rate of sexual initiation among the 469 virgins across the five categories of the self-reported likelihood of having sex. ?2 test was conducted to compare differences in the incidence rate across the five levels of self-reported likelihood and Cochran-Armitage Trend Test was conducted to assess the relationship between the self-reported likelihood and the actual sexual initiation. In addition to the incidence rate, the proportions of subjects who initiated sex were compared across the five categories of self-reported likelihood of having sex to illustrate the importance of CBC-based model in predicting sexual initiation. Finally, the incidence rates of sexual initiation by self-reported likelihood of having sex were compared between the control youth and the intervention youth to assess program effect.

The results from the analysis of five waves, twenty-four months of longitudinal follow-up of youth indicate that the process of sexual initiation among young adolescents follows the cusp catastrophe model. The beta coefficients of the key variables for the three proposed models were all statistically significant, particularly the ones for both the cubic and the bifurcation terms that support the cusp catastrophe. The greater R2 values from the cusp model than from the corresponding alternative linear models indicate the superiority of quantum behavior change than continuous behavior change in characterizing the process of sexual initiation among young adolescents. The improvement in model-data fitting could be that the QBC-based cusp model also contains a continuous component at the lower bifurcation variable levels that can capture much of the variance of SPI as in the linear models. In addition, there was a substantial number of participants in each of the three progression groups (approximately, 20% progressed backward, 30% progressed forward, and 50% no change). Such a distribution may have also contributed to the higher R2 for the cusp modeling than for linear modeling.

Research findings of this study add new empirical data supporting the importance of integrating the traditional linear and rational paradigm with the quantum and chaotic paradigm to advance health behavior research and prevention to curb the global epidemic of HIV/AIDS in the 21st Century.

Credits: Xinguang Chen,Sonja Lunn, Carole Harris, Xiaoming Li, Lynette Deveaux, Sharon Marshall, Leslie Cottrell, and Bonita Stanton

More information at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3013356/?tool=pubmed

 

 

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