Patterns of Age Mixing and Sexually Transmitted Infections Julie Kraut-Becher University of Pennsylvania Sevgi O. Aral Division of STD Prevention, CDC

Age Mixing Population-level determinant Population-level determinant –Spread of HIV Africa Africa Gay men Gay men Individual-level risk factor Individual-level risk factor –Risky behavior Unprotected vaginal sex Unprotected vaginal sex Lack of consistent condom use Lack of consistent condom use

Age Mixing Increase STI incidence Increase STI incidence –Directly Exposure to partner pools with higher STI prevalence Exposure to partner pools with higher STI prevalence –Indirectly Partnerships marked by power imbalance Partnerships marked by power imbalance –Practice of safer sex is difficult

Objectives Describe age mixing patterns Describe age mixing patterns –Nationally representative sample of reproductive age, sexually-active U.S. women Relate these patterns to self-reported STI history Relate these patterns to self-reported STI history –STI diagnosis or testing or treatment

Methods Data Data –1995 National Survey of Family Growth (NSFG) Sample Sample –N = 9,272 sexually-active women years of age Valid birth date information for themselves and their partner Valid birth date information for themselves and their partner

Methods Age Difference Age Difference –Computed for current or most recent partnership –Age difference < 0 Younger male partner Younger male partner –Age difference > 0 Older male partner Older male partner

Methods Assess extent of age mixing Assess extent of age mixing Describe patterns of age mixing Describe patterns of age mixing –Sociodemographic and socioeconomic characteristics –STI history Examine association between age mixing Examine association between age mixing and STI test, treatment, and diagnosis and STI test, treatment, and diagnosis Nationally representative sample Nationally representative sample –Sample weights

Results

Results

Results

Results

Results

Results

Results

Results

Results

Results year-old females year-old females

Results year-old females year-old females

Results year-old females year-old females

Results year-old females year-old females

Results year-old females year-old females

Results year-old females year-old females

Results year-old females year-old females

Limitations Self reports of STI information Self reports of STI information STI diagnoses not temporally defined STI diagnoses not temporally defined –Cannot determine the causal nature of association between partnership characteristics and STI

Conclusions Large extent of age mixing Large extent of age mixing Age mixing varies over the life course Age mixing varies over the life course The effect of age mixing on STI varies over the life course The effect of age mixing on STI varies over the life course

Conclusions Future research Future research –Biomarkers vs. self-reports –Specific infections –Race/ethnicity specific Program Program –Ask about age mixing with current sex partners Screening parameter Screening parameter Target interventions Target interventions