I chose to study how geographic and neighborhood characteristics can be used to plan HIV prevention interventions for high risk young adults in Los Angeles County.
Despite advances in HIV prevention, infection rates and numbers of new cases of HIV among adolescents continue to rise (Geanuracos et al., 2007). There were over 2,400 cases of HIV reported in Los Angeles County in 2008 and 58% of them were among persons aged 20-39 years. Because HIV incidence data from the LA County Department of Public Health is not available to the public, I used 2009 data from AIDSVu. The map above shows 2009 new cases of HIV or AIDS among persons aged 13-24 (AIDSVu, 2012).
Previous research has shown that areas of high prevalence and incidence of HIV are often characterized by high levels of racial/ethnic segregation and low socioeconomic status (Geanuracos et al., 2007). I used data from the 2009 U.S. Census to perform a hot spot analysis of areas of high HIV risk for young adults in LA County. I combined percent African American households, percent Latino or Hispanic households, percent Asian households, percent of persons aged 18-24, and household median income. Each map was converted to a raster and reclassified in order to create an HIV risk index. Each variable was weighted equally (20%).
I found that the area with the highest HIV risk for young adults is also the area that had the highest number of new cases of HIV or AIDS in 2009 among persons aged 13-24. These results indicate that spatial analysis is an effective way to determine high risk areas for contracting HIV. Including other variables such as sexual orientation or drug use may yield even more accurate results.
Next, I wanted to determine whether young adults in the high risk area had access to HIV prevention services. I geocoded HIV testing locations and used network analysis to determine how far young adults needed to travel to access these services. The analysis on the left shows services areas within a 5 and 10 minute drive from HIV testing locations. The analysis on the right shows service areas within a 5, 10, and 20 minute walk from HIV testing locations. Because Los Angeles is a metropolitan area with an extensive public transportation system, it is likely that nearly all young adults in the high risk area have access to HIV prevention services.
However, some young adults may not spend time traveling to an HIV testing location. Holloway, Cederbaum, Ajayi, and Shoptaw (2012) found that young men who have sex with men (YMSM) desire to receive HIV prevention information quickly and easily in social contexts that they are already attending with friends. Reisner et al. (2009) recommended that health and community service providers engage YMSM for HIV education and prevention at popular venues.
I wanted to know how information about popular venues that young adults frequent could be used to plan HIV prevention interventions in LA County. For this part of the analysis, I used data from the Healthy Young men (HYM) study (Kipke et al., 2007). The purpose of this study was to explore the individual, familial, interpersonal, and community factors that may influence drug use, HIV risk, and mental health. Participants included 526 young men who have sex with men (YMSM) who completed one survey every 6 months between February 2005 and January 2006. Data collection included demographic variables, sexual orientation, perceived health status, personal satisfaction, health behaviors, access to care, history of STIs and HIV, depression, suicidality, and favorite “gay places”. I used the favorite “gay places” variable to determine the ideal location for an HIV mobile testing unit for YMSM in LA County.
The above map shows the most popular venues among HYM study participants. I used spatial statistics to identify the central feature of these venues which is represented by the white star.
The above map shows the area with the greatest number of popular venues. Most of them are located in Hollywood and West Hollywood. West Hollywood is represented by the light gray color in the center of the map.
I again used spatial analysis to determine the ideal location for a mobile HIV testing unit. First, I used directional distribution to determine the area that included 68% (1 standard deviation) of the most popular venues in Hollywood and West Hollywood. Next, I used euclidean distance to measure distances from each venue and kernel density to measure densities based on total number of votes for each venue.
Finally, I used map algebra to combine the results of these analyses. I calculated the areas within 126 meters of a popular venue and with .0000358 votes per square meter.
The results of the analysis indicate that the ideal location for a mobile HIV testing unit is on Santa Monica Boulevard between Palm Avenue and North La Peer Drive or near Westmount Drive.
Interestingly, there is an actual HIV mobile testing unit every weekend on Santa Monica Boulevard near North San Vicente Boulevard (white star). Whether or not this location was selected using spatial analysis, it’s the perfect location to reach the greatest number of YMSM.
Thus, the results of these analyses indicate that geographic and neighborhood characteristics can be used to identify areas where young adults are at high risk for contracting HIV. Additionally, information about popular venues that young adults frequent can be used to identify ideal locations for HIV prevention interventions.
The above layout includes the models that I used to perform the hot spot analysis. I converted features to rasters and then reclassified them so that I could use the raster calculator.