Geographic variation of HIV infection in childbearing women with syphilis in the United States

Using spatial regression methods to examine the association between county-level racial/ethnic composition and reported cases of Chlamydia and gonorrhea: an illustration with data from the state of Texas

BACKGROUND

Several studies have reported racial/ethnic disparities in the incidence of sexually transmitted diseases. However, very few studies have accounted for potential spatial dependence. Additionally, little is known about the relative magnitudes of the associations between county-level racial/ethnic composition and the 2 most commonly reported sexually transmitted diseases.

METHODS

We used county-level data from the National Electronic Telecommunications System for Surveillance and the 2000 Census data to investigate the association between county-level racial/ethnic composition and reported cases of the 2 most commonly reported sexually transmitted diseases (chlamydia and gonorrhea) in Texas. We also estimated ordinary least square (OLS) models for comparison.

RESULTS

Preliminary results from the spatial regression models indicated that the choice of spatial relationships criteria was important for model specification. The spatial error model (SEM) was superior to the spatial autoregressive model, spatial Durbin model, and OLS. The SEM for the 2 disease equations were further analyzed using a seemingly unrelated regression estimation (SURE) procedure. Although the SEM was superior to all models (using standard criteria), the coefficients were fairly stable across models. Our results showed that a unit change in percent black was associated with 1.6 (1.1 for Hispanic) and 3.3 (0.5 for Hispanic) percent change in chlamydia and gonorrhea rates (on average), respectively, compared with percent white.

CONCLUSION

Although there were no substantial differences in the magnitude of the estimated parameters, spatial regression models are potentially superior to OLS models and should be explored in future sexually transmitted disease studies.

Social capital and rates of gonorrhea and syphilis in the United States: Spatial regression analyses of state-level associations

We conducted spatial regression analysis to account for spatial clustering of sexually transmitted diseases (STDs) and to examine the state-level association between social capital (using Putnam's public use data set) and rates of gonorrhea and syphilis. We conducted the analysis for the 48 contiguous states of the United States for 1990, 1995, and 2000 and controlled for the effects of regional variation in STD rates, and for state variation in poverty, income inequality, racial composition, and percentage aged 15-34 years. We compared the results of the spatial regression analysis with those of ordinary least squares (OLS) regression. Controlling for all population-level variables, the percentage of variation explained by the OLS regression and by the spatial regression were similar (mid-90s for gonorrhea and low-70s for syphilis), the standardized parameter estimates were similar, and the spatial lag parameter was not statistically significant. Social capital was not associated with STD rates when state variation in racial composition was included in the regression analysis. In this analysis, states with a higher proportion of residents who were African-American had higher STD rates. When we did not control for racial composition, regression analysis showed that states with higher social capital had lower STD rates. We conjecture that sexual networks and sexual mixing drive the association between social capital and STD rates and highlight important measurement and research questions that need elucidation to understand fully the relationship between social capital and STDs.

Incidence and risk factors for sexually transmitted infections among women in an Alabama HIV clinic

The objectives of this study were to assess the prevalence and incidence of curable sexually transmitted infections (STI), i.e., gonorrhea, chlamydial infection, or trichomoniasis, in a cohort of HIV-infected women. The study population was derived from women seeking primary care at an outpatient university HIV clinic who were participants in a women's natural history study. Enrollees (n = 225) were predominantly African-American, heterosexually infected, with mean age 35 years. Mean entry CD4+ T cell count was 405 cells/mm3. Over 6% were STI positive at initial screening. Subsequently, the combined curable STI incidence was 4.82/1000 woman-months over a median of 33 months of observation. Of 36 incident STIs, trichomoniasis was most common (n = 32). Predictors for acquisition of a curable STI included absenteeism at scheduled clinic appointments, RR = 1.99 (1.28, 3.08), and a higher CD4+ T cell count, RR = 1.15 (1.0028, 1.3115) for 100 cells. Interventions to prevent curable STI in HIV-infected women are warranted in primary care settings.

Characteristics of persons with syphilis in areas of persisting syphilis in the United States: sustained transmission associated with concurrent partnerships

BACKGROUND AND GOAL

In areas with persistent syphilis, to characterize persons at higher risk for transmitting syphilis.

STUDY DESIGN

Cohort study. Structured interviews of persons with early syphilis from four research centers were linked to outcomes of partner tracing.

RESULTS

Of 743 persons with syphilis, 229 (31%) reported two or more partners in the previous month, and 57 (8%) received money or drugs for sex in the previous three months. Persons with at least one partner at an earlier stage of syphilis than themselves were defined as transmitters; 63 (8.5%) of persons with early syphilis met this definition. Having concurrent partners (two or more in one week in the last month) was independently associated with being a transmitter.

CONCLUSION

Sexual network/behavioral characteristics of syphilis patients and their partners, such as concurrency, can help identify persons at higher risk for transmitting syphilis who should receive emphasis in disease prevention activities.