Decreasing age disparities in syphilis and gonorrhea incidence rates in the United States, 1981--2005.

BACKGROUND

Compared to older age groups, teenagers and young adults in the United States are at high risk of acquiring sexually transmitted diseases (STDs). Although the disparity in STD rates across age groups is well documented, changes in the degree of disparity in STD rates across age groups over time have not been examined in detail.

METHODS

We examined age-, sex-, and race-specific incidence rates of syphilis and gonorrhea in the United States (excluding New York owing to incomplete age- and race-specific data) from 1981 to 2005. STD rates in younger age groups (ages 15-29 years) were compared to STD rates in older age groups (ages 40-54 years) for each year over the 25-year period. We used regression analyses to examine the trend in the age rate ratio (STD rate in the younger age group divided by STD rate in the older age group) over time, adjusting for autocorrelation.

RESULTS

The age disparity in syphilis and gonorrhea declined from 1981 to 2005. The estimated annual decline in the age rate ratio was 5.3% for syphilis and 2.0% for gonorrhea for all races overall (P <0.01). Overall, the age disparity in STD rates was more pronounced for females than males.

CONCLUSIONS

Future research is needed to clarify the main determinants of the relative decline in STD rates in younger persons and to inform programmatic responses to the changing age disparity in STD rates.