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Estimation of Levels and Trends in Age at First Sex from Surveys Using Survival Analysis


Zaba, Basia W.; Boerma, J. Ties; Pisani, Elizabeth; & Baptiste, Nahum (2002). Estimation of Levels and Trends in Age at First Sex from Surveys Using Survival Analysis. Chapel Hill, N.C.: Carolina Population Center MEASURE.


Age at first sex is an important indicator of exposure to the risk of pregnancy and risk of sexually transmitted infections, including HIV, during adolescence. In fertility studies age at first marriage is often used as a proxy measure of the onset of a woman's exposure to pregnancy, but in many societies premarital sexual activity is common, and it has been proposed to use age at first sex as a better proxy (Stover 1998). In the context of the AIDS epidemic, accurate monitoring of trends in age at first sex has become even more important. Interventions target youth and promote postponement of first sex or discourage premarital sexual activity. In several countries, trends in HIV prevalence among pregnant women attending antenatal clinics have shown a decline in the younger age groups, while older women do not show such changes (Bunnell et al. 1999,Kilian et al. 1999). Such changes may be associated with changes in age at first sex, rates of partner change, sexual mixing patterns, and condom use. In Uganda, a rapid increase in age at first sex in urban areas between 1990 and 1995 was considered a major contributing factor in the observed HIV prevalence decline in young pregnant women from about 1993 (Asiimwe Okiror et al. 1997).

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Edited Book

Year Published



Zaba, Basia W.
Boerma, J. Ties
Pisani, Elizabeth
Baptiste, Nahum