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Background: CT is the most common reportable sexually transmitted infection in the U.S. Estimates of a woman’s lifetime risk of CT are limited.
Methods: We created lifetables to estimate the cumulative risk of testing positive for CT between the ages of 15 and 34 among women in King County, Washington. We used state surveillance data to define the number of women in each five year birth cohort with a first CT diagnosis during each year 1992-2014, and used census data to define the number women at risk during each year. We separately estimated risk among different racial/ethnicity groups.
Results: From 1992-2014, there were 71,352 CT infections reported among women aged 15-34, of which 51,464 were first infections. For women born 1975-1979, the cumulative risk of CT by age 34 was 18.1%. Among non-Hispanic Whites, non-Hispanic Blacks, and Hispanics born 1975-1979, the cumulative risk of CT by age 34 was 13.0%, 62.1%, and 29.8%, respectively. Among all women, the cumulative risk of CT increased among birth cohorts born 1975 to 1994; for women born 1975-1979, 1980-1984, 1985-1989, and 1990-1994 the risk of CT by age 23 was 13.2%, 14.1%, 15.0%, and 16.0%, respectively. However, this trend varied by race/ethnicity. Cumulative risk increased among non-Hispanic White and Hispanic women, but declined among non-Hispanic Blacks among whom cumulative risk by age 23 peaked at 55% among women born 1985-89, and declined to 37% among women born 1990-94.
Conclusions: The cumulative risk of CT infection varies dramatically by race/ethnicity, with over 60% of non-Hispanic Black women diagnosed with at least one infection by age 34 in the birth cohorts most affected by CT, a risk almost five times that observed in non-Hispanic Whites. Black-White disparities have declined over time as rates have increased modestly among Hispanics and non-Hispanic Whites while declining 33% among Blacks.