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A Closer Look at Age: Deconstructing Aggregate Gonorrhea and Chlamydia Rates, California, 1998–2007

Jacobs, Heather S. MPH*; Samuel, Michael C. DrPH; Chow, Joan M. DrPH; Bolan, Gail MD

Sexually Transmitted Diseases: May 2010 - Volume 37 - Issue 5 - p 328-334
doi: 10.1097/OLQ.0b013e3181c53363
Original Study

Background: Risk of gonorrheal (GC) and chlamydial (CT) infection is highly associated with age. Case rates typically are reported in 5-year categories. Highest rates are seen consistently in the 15- to 19-year and 20- to 24-year age groups for both genders. It is not clear how aggregate, age-specific rates mask finer differences in risk by single age across and within racial/ethnic groups.

Methods: California case-based surveillance data for 1998 through 2007 were used to calculate GC and CT rates by single age at diagnosis. The distribution of single gender and age-specific rates was compared with 5-year age-specific rates. Descriptive statistics for age by race/ethnicity were calculated, and trends over time were assessed.

Results: Female, single-age-specific GC and CT rates for 2007 increased strikingly during adolescence and then declined quickly. Male, single-age-specific GC rates declined more gradually than did CT rates. The rate for the aggregate 15- to 19-year-old age group fit the single-age rates poorly, particularly for females, who in 2007 had a peak rate at age 19 for GC (497 per 100,000) and for CT (3640 per 100,000), though the highest aggregate rate was for ages 20 to 24. Blacks had the youngest mean age for both GC and CT. Mean ages increased significantly from 1998 through 2007 for female GC and CT cases, as well as for male CT cases.

Conclusions: Age and race/ethnicity data should be examined in finer detail than the 5-year aggregate data, in order to target sexually transmitted disease prevention and control interventions more effectively.

Five-year age-specific gonorrhea and chlamydia case rates mask differences in rates by single age, particularly for adolescent females of color. Mean ages have increased over time for most groups.

From the *School of Public Health, University of California, Berkeley, CA; and †Sexually Transmitted Disease Control Branch, Division of Communicable Disease Control, Center for Infectious Diseases, California Department of Public Health, Richmond, CA

Correspondence: Michael C. Samuel, DrPH, Surveillance and Epidemiology Section, Sexually Transmitted Disease Control Branch, California Department of Public Health, 850 Marina Bay Parkway, Bldg. P, 2nd Floor, Richmond, CA 94804–6403. E-mail:

Received for publication July 20, 2009, and accepted October 8, 2009.

© Copyright 2010 American Sexually Transmitted Diseases Association