Sexual debut: an analysis of the birth to twenty data.
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Date
2015
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Abstract
According to the literature, it is widely accepted that the early timing of
first sex among adolescents is related to long-term health effects and current
and future risky sexual behaviour (Sandfort et al., 2008). Despite the
importance of youth sexual behaviour for sexual and reproductive health,
and the severity of the Human Immunodeficiency Virus (HIV) and the Acquired
Immune Deficiency Syndrome (AIDS), there exists relatively little
empirical research on sexual debut in Southern Africa (Muula, 2008). The
aim of this dissertation is to utilize survival analysis techniques to determine
significant predictors of early sexual debut in a South African context.
A collaboration with the Human Sciences Research Council (HSRC) was
fostered and access to the Birth to Twenty (Bt20) data was arranged. The
data set consists of 3273 respondents who were followed from birth. Sexual
exposure measures were recorded in six collection waves, namely 11-12,
13, 14, 15, 16 and 17-18 years.
Multivariate analyses were initially run by employing a standard survival
analysis technique, namely Cox proportional hazards regression survival
analysis for sexual debut. Analyses were run separately for males and
females. A log-rank test showed that there was a significant difference
between the survivor curves for voluntary sexual debut and involuntary
sexual debut. This result prompted consideration to explore a competing
risks regression model with voluntary sexual debut as the event of interest
and involuntary sexual debut as the competing risk event.
SPSS was used to run exploratory analyses and Cox Regression (IBM Corp,
2012). Regression diagnostic plots were run in SAS (SAS Institute Inc,
2004). Competing risks regression was performed according to the method
of Fine & Gray (1999) by evoking the STCRREG command in STATA and
the validity of the proportional subhazards assumption was tested by including
time interaction variables in the model (StataCorp, 2013). Where
violations of the proportional subhazards assumption were found, the varyi
ing effect of the hazard functions on the time to sexual debut was interpreted
accordingly.
Description
Master of Science in Mathematics, Statistics and Computer Science. University of KwaZulu-Natal, Durban 2015.
Keywords
Theses - Statistics.