Young age at first intercourse and risk-taking behaviours--a study of nearly 65 000 women in four Nordic countries.

Background: Risk-taking behaviours such as early initiation of smoking, alcohol drinking and sexual activity often cluster within individuals and could be characteristics of adolescents who in general are risk takers. In the present study, using a large population-based sample of 64 659 women aged 18-45 years in four Nordic countries, we investigate whether young age at first sexual intercourse is associated with subsequent risk-taking behaviours.

Methods: We examined the association between young age at first sexual intercourse (age ≤14 years) and subsequent risk-taking behaviours by using multivariate logistic regression by which odds ratios (ORs) and the corresponding 95% confidence intervals (95% CIs) were estimated.

Results: The OR of reporting more than 10 lifetime sexual partners was almost four times higher among women who reported a young age at first intercourse (OR = 3.79; 95% CI: 3.60-4.00) in comparison with women >14 years at first intercourse. Furthermore, women who were young at first intercourse were more likely to report two or more recent partners (OR = 1.67; 95% CI: 1.54-1.82) and to have a history of STIs (OR = 2.03; 95% CI: 1.93-2.13). In addition, young age at first intercourse was associated with current smoking (OR = 2.31; 95% CI: 2.20-2.43) and binge drinking (OR = 1.36; 95% CI: 1.28-1.44). All ORs were adjusted for age, years of education and country of residence.

Conclusion: Young age at first intercourse is associated with subsequent risk-taking behaviours. Our study emphasizes the importance of targeting prevention efforts towards the complexity of risk-taking behaviours.