Sociodemographic Distribution of Gonorrhea Incidence: Implications for Prevention and Behavioral Research
l.--..--.l.l-.-.-.
Roselyn J. Rice, MD, Pacita L. Roberts, MS, H. Hunter Hands-field, MD, and King K Holmes, MD, PhD
Introduction
Methods
With the advent of effective contraception, the onset of sexual maturity in the baby boom generation, and changes in sexual behavior, reported cases of gonorrhea increased at about 15% per year from the 1960s through the mid-1970s in the United States.1,2 Reported cases have gradually fallen since 1975.3 After 1982 a steady decline in rectal gonorrhea in men was observed in King County, Washington, and in other areas of the United States,4,5 implying a decline in gonorrhea among homosexually active men. Further analysis of trends in occurrence of gonorrhea by age, gender, and race for the period 1980 through 1988 in King County has shown more than a threefold decline in cases occurring in White men, little change in White women, but a steady increase in Black men and women from 1982 through 1988 (authors' unpublished data). Among Blacks, the greatest increase in annual cases has occurred among teenagers. This unexpected increase in gonorrhea in Blacks and the concurrent leveling off of reported cases in White women after nearly a decade of decline led us to undertake a 2-year intensive surveillance of gonorrhea in Seattle-King County to define incidence rates in population subgroups according to age, gender, race or ethnicity, residence (urban, suburban, or rural), and socioeconomic status (SES). The results are useful not only for defining more precisely a current profile of individuals at highest risk for gonorrhea, but also as a proxy measure of the distribution of sexual behaviors that place individuals at risk for all sexually transmitted diseases, including the acquired immunodeficiency syndrome (AIDS).
Surveillance and Case Reporting King County, Washington (population 1.4 million, 2130 square miles), encompasses the city of Seattle (population 496 000). Health care providers in King County are required to report all gonorrhea cases; compliance is 100% by Seattle-King County Department of Public Health (DPH) clinics, but variable by other clinics and the private health care sector.
Surveillance Beginning in 1985, presentations to microbiology laboratory directors, monthly bulletins of the DPH, newsletters and bulletins of the King County Medical Society, and hospital staff meetings were used to publicize the enhanced gonorrhea surveillance project and encourage compliance with effective culture diagnosis and case reporting. Routine case reporting was supplemented by active laboratory surveillance for Neissena gonorhoeae in All authors are with the Department of Medi-
cine, Harborview Medical Center, and the University of Washington School of Medicine; H. Hunter Handsfield is with the Seattle-King County Department of Public Health, Seattle; and Roselyn Rice is with the Division of Sexually Transmitted Diseases Laboratory Research, Center for Infectious Diseases, Centers for Disease Control, Atlanta Requests for reprints should be sent to King K. Holmes, MD, PhD, Harboiview Medical Center, 325 Ninth Avenue, Seattle, WA 98104. This paper was submitted to the journal March 21, 1990, and accepted with revisions February 26, 1991. Editor's Note. See related Editorial by Richard Rothenberg on page 1250 of this issue of the journal.
October 1991, Vol. 81, No. 10
Sociodemographic Distribution of Gononihea
laboratories in King County through a system established with the DPH central laboratory. Hospital, private physician, and commercial laboratories were asked to submit all positive and confirmatory culture isolates for N. gonorrioeae to the DPH laboratory for confirmation and antimicrobial susceptibility screening tests. The DPH processed 56 353 cultures for N. gononroeae in 1986 and 52 844 in 1987. During 1986 and 1987, gonococcal isolateswere received from 14 hospitals, 4 private microbiology laboratories, 2 student health clinics, 2 military health clinics, all 12 DPH clinics, 22 community clinics (partially supported by DPH), the Seattle-King County Jail and Juvenile Detention Center, 6 private family planning clinics, and numerous physicians' offices. Of the cultures confirmed as positive for N. gonordhoeae, 47.0% were submitted from DPH clinics, 22.2% from private physicians, 20.4% from hospitals, 6.0%o from community clinics, 3.6% from private family planning clinics, 0.6% from student health clinics, and 0.1% from military clinics. Matching of positive cultures confirmed by the DPH laboratory with submitted case reports from all public and private providers indicated that cultures were submitted to the DPH laboratory for confirmation from 78% of the reported gonorrhea cases in the study population.
Case Reporting Gonorrhea case reports were submitted to the DPH using Centers for Disease Control (CDC) form 73.688 (revised 1/86). Following notification of a case of gonorrhea by case report form or as a result of laboratory surveillance, when necessary, DPH staffcontacted health care providers for additional demographic information on age, gender, race or ethnicity, address, anatomic site of infection, date of infection, date of treatment, and clinical diagnosis
(asymptomatic gonorrhea, symptomatic gonorrhea, pelvic inflammatory disease [PID], disseminated gonococcal infection [DGI], adult conjunctivitis).
Demographic Classification Data from case reports were abstracted and analyzed for all individuals with gonorrhea who resided in King County at the time of diagnosis. Residence was classified as urban for persons residing within the geographic boundaries of Seattle and as suburban for persons living in incorporated areas of King County or in census tracts with population densities of more than 2000 persons per square mile (based on 1980 US Census statistics).
October 1991, Vol. 81, No. 10
The remainder were classified as rural King County residents. Race and ethnicity were classified according to the CDC case report form 73.688 as White, Black, Hispanic, Asian/Pacific Islander, Native American/Eskimo, or other. Hispanics were classified separately, regardless of race designation.
Socioeconomic Categonzation of Census Tract of Residence Census tracts in Seattle were divided into four socioeconomic categories on the basis of the following population characteristics summarized from the 1980 US Census on Population and Housing: (1) median family income; (2) percent that completed high school; (3) percent employed in professional, managerial, or technical occupations; (4) housing cost index; and (5) percent in owner-occupied housing. A score was computed for each tract from the sum of the tract rankings according to the stated characteristics, and these scores were used to categorize tracts into low, lower-middle, upper-middle, and high SES groupings. These four groupings comprised 25.5%, 28.2%, 18.7%, and 27.6% of the city population, respectively.
Calculation of Gononhea Incidence Incidence rates for gonorrhea were calculated using the total number of cases reported to the Seattle-King County DPH in the 2-year period 1986 to 1987, divided by the total county population count from the 1980 US Census of King County population. This was halved to arrive at an annual rate. Incidence rates by gender, age, race or ethnicity, and census tract of residence were calculated in the same way, using 1980 US Census Bureau data for King County.6
Calculation of Estimated Incidence Rates by Manital Status Marital status was not known for 50% of cases reported from sources other than DPH clinics. In order to estimate incidence rates for marital status, the distribution of marital status for cases where this was known was applied to the unknowns.
Calculation ofAdjusted Incidence
Rates for Sexually E epenenced Women Gonorrhea rates were calculated for women of White and other races using as denominators national estimates of the number of women who were sexually experienced, as reported in the 1982 Na-
tional Survey of Family Growth Report;7 these estimates were adjusted for the number of women in King County in 1980 by age and race.
Statistical Analysis Correlation between incidence rates and population density in census tracts was examined statistically by computing the correlation coefficient (r).
Resuls Incidence of Gononhea by Age, Gender, Race, Residence, and Marital Status Gender and Age Group. The overall annualized incidence rates of gonorrhea by gender were 293 per 100 000 for men and 286 per 100 000 for women. As summarized in Figure 1, the incidence of gonorrheawas highest in females aged 16to 19 years. For ages 16 to 17 years, incidence rates of gonorrhea were four times higher for females than for males. In contrast, gonorrhea incidence among men was more broadly distributed across age groups, but was higher for men than for women above age 24. Men and women in the 22- to 24-year-old age group had similar rates of gonorrhea. Race and Ethnicity. Of the 7342 reported gonorrhea cases, 39.6% involved Whites, 48.8% Blacks, 3.3% Native Americans, 3.5% Asians and Pacific Islanders, and 4.9% Hispanics. The annual incidence of gonorrhea per 100 000 by race or ethnicity is shown in Table 1. There were remarkable differences among racial and ethnic groups in the age and gender distnbution of gonorrhea incidence. Among men, the peak incidence of gonorrhea per 100 000 was observed at age 19 for Blacks (11 266) and Native Americans (2299), age 20 for Asians and Pacific Islanders (807), age 21 for Whites (283), and ages 22 to 24 for Hispanics (2597). Among women, the peak incidence per 100 000 was observed at age 18 for Blacks (12 848), Whites (729), and Hispanics (906), and age 19 for Native Americans and Eskimos (6250) and Asians and Pacific Islanders (1068). The overall male:female ratio for gonorrhea incidence was 1.18 for Blacks, 0.73 for Whites, 0.48 for Native Americans, 1.50 for Asians and Pacific Islanders, and 3.51 for Hispanics. As shown in Figure 2, the gender ratio for gonorrhea incidence followed a similar pattern for Whites and Blacks, with females predominating at younger ages and males predominating at ages 25 to 29 years American Journal of Public Health 1253
Rim et al.
1,500
O Male
1,250 0
1
U Female
1,000o
o
ci
-
0
7500.0
tracts.
2$500
Annual incidence rates according to race or ethnicity and SES are shown in Table 1. Within each racial or ethnic group, there was an inverse and statisti-
0
Age FIGURE 1-Annual In nce of rrhea per 100 000 popubaIon for Seatde-Kng County residents by gender and age group, 1986-1987.
and above for both groups. However, for Hispanics, rates for females exceeded rates for males only for ages 17 years and under and were about threefold to sixfold lower after age 21. Similarly, for Asians and Pacific Islanders, the incidence in males exceeded that for females for all ages after age 19 and remained low thereafter. In contrast, for Native Americans the incidence rates for females were higher than incidence rates for males for all ages up to 35 years. These differences are large, but are based on relatively small numbers of cases involving Hispanics, Asians and Pacific Islanders, and Native Americans and Eskimos. The differences could also be influenced by underreporting of male cases, as discussed below. Marital Status. The annual adjusted incidence of gonorrhea per 100 OOOwas 42
1254 American Joumal of Public Health
Socioeconomic Status. In Seattle, which we defined as urban, the population living in low SES census tracts represented only 25.5% of the population but accounted for 58% of the reported gonorrhea. There were 2870 cases in 125 143 residents of low SES census tracts, 1164 cases among 138 294 residents of lowermiddle SES census tracts, 409 cases among 91 407 residents of upper-middle SES census tracts, and 494 cases among 135 262 residents of high SES census
for married men; 67 for divorced, separated, or widowed men; and 1018 for never-married men. The incidence per 100 000 was 33 for married women, 21 for divorced, separated, or widowed women; and 1275 for never-married women. We did not adjust further for marital status in subsequent analyses because data on marital status were not available for all cases. Urban, Suburban, and Rural Residents. Of the 7342 gonorrhea cases included in this analysis, 74% occurred in urban (i.e., Seattle) residents, 19% in residents of suburban census tracts with >2000 residents per square mile, and 7% in residents of rural census tracts (
l.--..--.l.l-.-.-.
Roselyn J. Rice, MD, Pacita L. Roberts, MS, H. Hunter Hands-field, MD, and King K Holmes, MD, PhD
Introduction
Methods
With the advent of effective contraception, the onset of sexual maturity in the baby boom generation, and changes in sexual behavior, reported cases of gonorrhea increased at about 15% per year from the 1960s through the mid-1970s in the United States.1,2 Reported cases have gradually fallen since 1975.3 After 1982 a steady decline in rectal gonorrhea in men was observed in King County, Washington, and in other areas of the United States,4,5 implying a decline in gonorrhea among homosexually active men. Further analysis of trends in occurrence of gonorrhea by age, gender, and race for the period 1980 through 1988 in King County has shown more than a threefold decline in cases occurring in White men, little change in White women, but a steady increase in Black men and women from 1982 through 1988 (authors' unpublished data). Among Blacks, the greatest increase in annual cases has occurred among teenagers. This unexpected increase in gonorrhea in Blacks and the concurrent leveling off of reported cases in White women after nearly a decade of decline led us to undertake a 2-year intensive surveillance of gonorrhea in Seattle-King County to define incidence rates in population subgroups according to age, gender, race or ethnicity, residence (urban, suburban, or rural), and socioeconomic status (SES). The results are useful not only for defining more precisely a current profile of individuals at highest risk for gonorrhea, but also as a proxy measure of the distribution of sexual behaviors that place individuals at risk for all sexually transmitted diseases, including the acquired immunodeficiency syndrome (AIDS).
Surveillance and Case Reporting King County, Washington (population 1.4 million, 2130 square miles), encompasses the city of Seattle (population 496 000). Health care providers in King County are required to report all gonorrhea cases; compliance is 100% by Seattle-King County Department of Public Health (DPH) clinics, but variable by other clinics and the private health care sector.
Surveillance Beginning in 1985, presentations to microbiology laboratory directors, monthly bulletins of the DPH, newsletters and bulletins of the King County Medical Society, and hospital staff meetings were used to publicize the enhanced gonorrhea surveillance project and encourage compliance with effective culture diagnosis and case reporting. Routine case reporting was supplemented by active laboratory surveillance for Neissena gonorhoeae in All authors are with the Department of Medi-
cine, Harborview Medical Center, and the University of Washington School of Medicine; H. Hunter Handsfield is with the Seattle-King County Department of Public Health, Seattle; and Roselyn Rice is with the Division of Sexually Transmitted Diseases Laboratory Research, Center for Infectious Diseases, Centers for Disease Control, Atlanta Requests for reprints should be sent to King K. Holmes, MD, PhD, Harboiview Medical Center, 325 Ninth Avenue, Seattle, WA 98104. This paper was submitted to the journal March 21, 1990, and accepted with revisions February 26, 1991. Editor's Note. See related Editorial by Richard Rothenberg on page 1250 of this issue of the journal.
October 1991, Vol. 81, No. 10
Sociodemographic Distribution of Gononihea
laboratories in King County through a system established with the DPH central laboratory. Hospital, private physician, and commercial laboratories were asked to submit all positive and confirmatory culture isolates for N. gonorrioeae to the DPH laboratory for confirmation and antimicrobial susceptibility screening tests. The DPH processed 56 353 cultures for N. gononroeae in 1986 and 52 844 in 1987. During 1986 and 1987, gonococcal isolateswere received from 14 hospitals, 4 private microbiology laboratories, 2 student health clinics, 2 military health clinics, all 12 DPH clinics, 22 community clinics (partially supported by DPH), the Seattle-King County Jail and Juvenile Detention Center, 6 private family planning clinics, and numerous physicians' offices. Of the cultures confirmed as positive for N. gonordhoeae, 47.0% were submitted from DPH clinics, 22.2% from private physicians, 20.4% from hospitals, 6.0%o from community clinics, 3.6% from private family planning clinics, 0.6% from student health clinics, and 0.1% from military clinics. Matching of positive cultures confirmed by the DPH laboratory with submitted case reports from all public and private providers indicated that cultures were submitted to the DPH laboratory for confirmation from 78% of the reported gonorrhea cases in the study population.
Case Reporting Gonorrhea case reports were submitted to the DPH using Centers for Disease Control (CDC) form 73.688 (revised 1/86). Following notification of a case of gonorrhea by case report form or as a result of laboratory surveillance, when necessary, DPH staffcontacted health care providers for additional demographic information on age, gender, race or ethnicity, address, anatomic site of infection, date of infection, date of treatment, and clinical diagnosis
(asymptomatic gonorrhea, symptomatic gonorrhea, pelvic inflammatory disease [PID], disseminated gonococcal infection [DGI], adult conjunctivitis).
Demographic Classification Data from case reports were abstracted and analyzed for all individuals with gonorrhea who resided in King County at the time of diagnosis. Residence was classified as urban for persons residing within the geographic boundaries of Seattle and as suburban for persons living in incorporated areas of King County or in census tracts with population densities of more than 2000 persons per square mile (based on 1980 US Census statistics).
October 1991, Vol. 81, No. 10
The remainder were classified as rural King County residents. Race and ethnicity were classified according to the CDC case report form 73.688 as White, Black, Hispanic, Asian/Pacific Islander, Native American/Eskimo, or other. Hispanics were classified separately, regardless of race designation.
Socioeconomic Categonzation of Census Tract of Residence Census tracts in Seattle were divided into four socioeconomic categories on the basis of the following population characteristics summarized from the 1980 US Census on Population and Housing: (1) median family income; (2) percent that completed high school; (3) percent employed in professional, managerial, or technical occupations; (4) housing cost index; and (5) percent in owner-occupied housing. A score was computed for each tract from the sum of the tract rankings according to the stated characteristics, and these scores were used to categorize tracts into low, lower-middle, upper-middle, and high SES groupings. These four groupings comprised 25.5%, 28.2%, 18.7%, and 27.6% of the city population, respectively.
Calculation of Gononhea Incidence Incidence rates for gonorrhea were calculated using the total number of cases reported to the Seattle-King County DPH in the 2-year period 1986 to 1987, divided by the total county population count from the 1980 US Census of King County population. This was halved to arrive at an annual rate. Incidence rates by gender, age, race or ethnicity, and census tract of residence were calculated in the same way, using 1980 US Census Bureau data for King County.6
Calculation of Estimated Incidence Rates by Manital Status Marital status was not known for 50% of cases reported from sources other than DPH clinics. In order to estimate incidence rates for marital status, the distribution of marital status for cases where this was known was applied to the unknowns.
Calculation ofAdjusted Incidence
Rates for Sexually E epenenced Women Gonorrhea rates were calculated for women of White and other races using as denominators national estimates of the number of women who were sexually experienced, as reported in the 1982 Na-
tional Survey of Family Growth Report;7 these estimates were adjusted for the number of women in King County in 1980 by age and race.
Statistical Analysis Correlation between incidence rates and population density in census tracts was examined statistically by computing the correlation coefficient (r).
Resuls Incidence of Gononhea by Age, Gender, Race, Residence, and Marital Status Gender and Age Group. The overall annualized incidence rates of gonorrhea by gender were 293 per 100 000 for men and 286 per 100 000 for women. As summarized in Figure 1, the incidence of gonorrheawas highest in females aged 16to 19 years. For ages 16 to 17 years, incidence rates of gonorrhea were four times higher for females than for males. In contrast, gonorrhea incidence among men was more broadly distributed across age groups, but was higher for men than for women above age 24. Men and women in the 22- to 24-year-old age group had similar rates of gonorrhea. Race and Ethnicity. Of the 7342 reported gonorrhea cases, 39.6% involved Whites, 48.8% Blacks, 3.3% Native Americans, 3.5% Asians and Pacific Islanders, and 4.9% Hispanics. The annual incidence of gonorrhea per 100 000 by race or ethnicity is shown in Table 1. There were remarkable differences among racial and ethnic groups in the age and gender distnbution of gonorrhea incidence. Among men, the peak incidence of gonorrhea per 100 000 was observed at age 19 for Blacks (11 266) and Native Americans (2299), age 20 for Asians and Pacific Islanders (807), age 21 for Whites (283), and ages 22 to 24 for Hispanics (2597). Among women, the peak incidence per 100 000 was observed at age 18 for Blacks (12 848), Whites (729), and Hispanics (906), and age 19 for Native Americans and Eskimos (6250) and Asians and Pacific Islanders (1068). The overall male:female ratio for gonorrhea incidence was 1.18 for Blacks, 0.73 for Whites, 0.48 for Native Americans, 1.50 for Asians and Pacific Islanders, and 3.51 for Hispanics. As shown in Figure 2, the gender ratio for gonorrhea incidence followed a similar pattern for Whites and Blacks, with females predominating at younger ages and males predominating at ages 25 to 29 years American Journal of Public Health 1253
Rim et al.
1,500
O Male
1,250 0
1
U Female
1,000o
o
ci
-
0
7500.0
tracts.
2$500
Annual incidence rates according to race or ethnicity and SES are shown in Table 1. Within each racial or ethnic group, there was an inverse and statisti-
0
Age FIGURE 1-Annual In nce of rrhea per 100 000 popubaIon for Seatde-Kng County residents by gender and age group, 1986-1987.
and above for both groups. However, for Hispanics, rates for females exceeded rates for males only for ages 17 years and under and were about threefold to sixfold lower after age 21. Similarly, for Asians and Pacific Islanders, the incidence in males exceeded that for females for all ages after age 19 and remained low thereafter. In contrast, for Native Americans the incidence rates for females were higher than incidence rates for males for all ages up to 35 years. These differences are large, but are based on relatively small numbers of cases involving Hispanics, Asians and Pacific Islanders, and Native Americans and Eskimos. The differences could also be influenced by underreporting of male cases, as discussed below. Marital Status. The annual adjusted incidence of gonorrhea per 100 OOOwas 42
1254 American Joumal of Public Health
Socioeconomic Status. In Seattle, which we defined as urban, the population living in low SES census tracts represented only 25.5% of the population but accounted for 58% of the reported gonorrhea. There were 2870 cases in 125 143 residents of low SES census tracts, 1164 cases among 138 294 residents of lowermiddle SES census tracts, 409 cases among 91 407 residents of upper-middle SES census tracts, and 494 cases among 135 262 residents of high SES census
for married men; 67 for divorced, separated, or widowed men; and 1018 for never-married men. The incidence per 100 000 was 33 for married women, 21 for divorced, separated, or widowed women; and 1275 for never-married women. We did not adjust further for marital status in subsequent analyses because data on marital status were not available for all cases. Urban, Suburban, and Rural Residents. Of the 7342 gonorrhea cases included in this analysis, 74% occurred in urban (i.e., Seattle) residents, 19% in residents of suburban census tracts with >2000 residents per square mile, and 7% in residents of rural census tracts (
