Rural counties chlamydia and gonorrhea rates in Pennsylvania among adolescents and young adults.

BACKGROUND: American adolescents and young adults between the ages of 15 and 24 account for 50% of all sexually transmitted diseases (STDs) annually. Rural populations in this age group are often understudied, despite having factors that place them at higher risk for STDs.

PURPOSE: The purpose of this study was to evaluate the utility of time series analysis in the assessment of rural Pennsylvania county-level chlamydia and gonorrhea rates overtime (2004-2014) for 15- to 19- and 20- to 24-year-old age groups by gender.

METHODS: An exploratory analysis was completed using Pennsylvania STD surveillance case report and census data, to develop a linear mixed-effects model of the STD rate for each Pennsylvania county for the years 2004 through 2014 using 3-month increments. A cubic polynomial spline regression model was assumed over the 44 time points for each county to account for possible oscillations in the STD rate during the 11-year period.

RESULTS: Eight out of 12 rural counties had a significant increase in chlamydia or gonorrhea rates, and five rural counties had significant decreases in chlamydia or gonorrhea rates from 2004 to 2014.

CONCLUSIONS: Results from this study provide the first analysis of change in rates of STDs in rural settings and demonstrate the utility of time series analysis for populations with small sample sizes.