Harris MA et al., 2008 · J Adolesc Health
Studies from around the world indicate a trend toward younger ages of menarche. The extent of this trend in the Canadian population is unknown, and the relationship to later-life health indicators has not yet been fully elucidated. The objective of this study is to estimate the trend in age at menarche (AAM) in the Canadian population and evaluate the relationship between AAM and adult body mass index (BMI). Our data source was a nationally representative survey (the Canadian Community Health Survey, 2.2), and analyses included 8080 women, aged 15 and older, who self-reported AAM. Height and weight were measured by the interviewers for the calculation of current BMI. We modeled the secular trend in AAM over time, and the relationship between current BMI and AAM. We found a statistically significant decline in AAM in successive age cohorts, indicating a 0.73-year (8.8-month) decrease in AAM between the oldest and youngest age cohorts in the sample. A 1-year increase in AAM was associated with a decrease in mean BMI of approximately 0.5 kg/m(2), after adjustment for covariates. A current age-AAM interaction term was nonsignificant, indicating that the relationship was stable throughout increasing temporal separation from puberty. The observed trend toward earlier menarche could be an indicator of a change in insulin-related metabolism, possibly mediated by behavioral and environmental variables. This study suggests that AAM may be an important clinical and public health indicator of susceptibility to overweight and obesity and attendant morbidity.
Cabezón C et al., 2005 · J Adolesc Health
To evaluate the efficacy of an abstinence-centered sex education program in adolescent pregnancy prevention, the TeenSTAR Program was applied in a high school in Santiago, Chile. A total of 1259 girls from a Santiago high school were divided into three cohorts depending on the year they started high school: the 1996 cohort of 425 students, which received no intervention; the 1997 cohort, in which 210 students received an intervention and 213 (control group) did not; and the 1998 cohort, in which 328 students received an intervention and 83 (control group) did not. Students were randomly assigned to control and intervention groups in these cohorts, before starting with the program. We conducted a prospective, randomized study using the application of the TeenSTAR sex education program during the first year of high school to the intervention groups in the 1997 and 1998 cohorts. All cohorts were followed up for 4 years; pregnancy rates were recorded and subsequently contrasted in the intervention and control groups. Pregnancy rates were measured and Risk Ratio with 95% confidence interval were calculated for intervention and control groups in each cohort. Pregnancy rates for the intervention and control groups in the 1997 cohort were 3.3% and 18.9%, respectively (RR: 0.176, CI: 0.076-0.408). Pregnancy rates for the intervention and control groups in the 1998 cohort were 4.4% and 22.6%, respectively (RR 0.195, CI: 0.099-0.384). The abstinence-centered TeenSTAR sex education intervention was effective in the prevention of unintended adolescent pregnancy.