From 1996 through 2004, most of the 24 states had relatively high percentages of schools teaching sexuality education topics, except for how to use a condom, which was taught to a much lower degree ().
In 1997, the mean (SD) birthrate for girls aged 15 to 17 years old was 25.6 (8.4) births per 1000 girls; this gradually decreased to 17.7 (5.4) births per 1000 girls in 2005 (). Other state demographic and political variables are presented averaged over time by state in . New Hampshire had the lowest mean adolescent birthrate during the study period (9.7 births per 1000 girls), whereas Arkansas had the highest (34.8). Alaska had the lowest average score of all sexuality education topics taught (68.8%), whereas New York had the highest (91.0%).
Mean birthrates for girls aged 15 to 17 years over time for included states.
There was a significant inverse relationship between a state’s religiosity and the percentage of schools in the state teaching condom efficacy or how to correctly use a condom (averaged over time), indicating the more religious the state, the less condom education was taught (condom efficacy r=−0.48; P=.02; correct condom use r=−0.58; P=.003). The political ideology of a state was significantly associated with most of the sexuality education topics (significant r ranged from 0.43 to 0.68), indicating that the more liberal the state, the more sexuality education topics were taught. Political ideology was explored as a potential covariate in multivariable models but was not retained in the analysis because it was highly correlated with the sexuality education topics.
Results are presented in for within- and between-state effects for each sexuality education topic, first in univariate analysis and then in a multivariable analysis that adjusts for time trend, state demographic variables, and state religious/abortion law variables, in that order. For time-varying covariates, within-state effects are represented in the model by the state’s time-varying deviation around its mean, and between-state effects are represented in the model by the state’s mean on the time-varying covariate. Adolescent birthrates over time could not be explained by within-state changes in most of the sexuality education topics over time, evidenced by the nonsignificance of the within-state effects of the sexuality education topics even in univariate analysis. The within-state effect of HIV infection prevention became significant in the final model, indicating that increasing education on HIV infection prevention within a state over time is associated with lower birthrates. Two states, Alabama and Idaho, increased their HIV infection prevention education over time to nearly perfect so that essentially all schools taught HIV infection prevention (Alabama from 94% to 100% and Idaho from 92% to 99%) and were thus influential in this finding. These states were not excluded from the model; however, more years of data with more states exhibiting changes in this topic over time may be necessary to validate these findings.
Sexuality Education Topics Related to Birthrates for 15- to 17-Year-Old Girls, 1997–2005
Many significant associations were found for between-state effects in univariate analysis. States with higher average percentages of schools teaching sexuality education topics had lower birthrates on average. Significant associations between sexuality education topics and adolescent birthrates were found for the states’ average score of all topics taught and for 8 of the 13 topics (ie, HIV infection prevention, pregnancy prevention, sexually transmitted disease prevention, abstinence as the most effective method to avoid HIV infection, how HIV is transmitted, condom efficacy, how to correctly use a condom, and human sexuality). For example, a 1% increase in the states’ average score of all topics taught was associated with 0.6 fewer births per 1000 girls aged 15 to 17 years (P =.001).
Adding time trend to the model had a minimal effect on the associations between the sexuality education topics and adolescent birthrates (step 1); however, for many of the sexuality education topics, the between-state effects lost significance when adjusting for both time trend and the demographic characteristics of the state (step 2). Specifically, this pattern was observed for HIV infection prevention, pregnancy prevention, sexually transmitted disease prevention, abstinence, how HIV is transmitted, and human sexuality. In the final step (step 3), adding the religious/abortion law variables to the model eliminated the remaining significant between-state effects for the states’ average score of all topics taught and how to correctly use a condom. The between-state effect of condom efficacy changed from being associated with lower adolescent birthrates to being associated with higher birth-rates when adding the religiosity and abortion law variables. The strong correlation of religiosity and abortion laws with condom efficacy may be causing the effect to turn in the opposite direction. The between-state effect of the influence of alcohol/drugs on HIV-related risk behaviors becomes significant when adjusting for all covariates, indicating that states teaching this topic in more schools have lower birthrates. This may be a true finding; however, this topic was queried only in the year 2002 and beyond, resulting in a model using only 3 years of data. This finding would need validation with more data. Of note, Delaware was excluded from specific HIV topic models (ie, HIV infection prevention, abstinence to avoid HIV, how HIV is transmitted, number of young people who contract HIV, and how to find information related to HIV) because it was disproportionately influential, indicated by large residuals (predicted adolescent birth-rates were much lower than observed adolescent birth-rates), large Cook’s distance values, and large fixed-effects deletion estimates for these sexuality education topics.
Many state characteristics were significantly associated with adolescent birthrates in the full models. As an illustration, we provide details on the model that included the states’ average score of all topics taught. Within-state differences in race were significantly associated with birthrates; the higher the proportion of whites, the lower the birthrates (β=−0.58; P =.03). Between-state differences in poverty were also significant, with a higher average poverty level associated with a higher adolescent birthrate (β=0.56; P =.005). Higher religiosity of a state was associated with higher adolescent birthrates (β=0.25; P=.01). Compared with parental consent adolescent abortion laws, having no adolescent abortion law was significantly associated with lower adolescent birthrates (no law β =−7.2; P =.04).