Geospatial research can help scientists and public health officials better understand a diverse range of health risks and outcomes. In their recent paper published in Geospatial Health, however, Columbia’s Spatial Epidemiology Lab (led by Dustin Duncan) points out that the bulk of existing geospatial health research has focused solely on where people’s homes are located, and in doing so ignored all the other places where people carry out their lives. Think about your own movements over the past week: it’s likely that you have spent time in numerous neighborhoods that include where your house or apartment is located but also where you work, go to school, run errands and socialize.
Experts in geospatial health have referred to the tendency of researchers to focus on home neighborhoods as the ‘residential trap’. To escape from this trap, William Goedel (lab affiliate) conducted a small study that asked 14 transgender women based in New York City to carry global positioning system (GPS) devices for one week. During that week the devices used GPS’s satellite-based technology to log location coordinates every 10 seconds, creating a dataset with which to identify the neighborhoods that participants visited and moved through.
The GPS devices proved to be very important. Participant’s had considerable mobility beyond their home neighborhoods. Every participant visited at least two different New York City boroughs and had ‘activity spaces’ (the area covered by their movements throughout the week) ranging from around 1.5 to 19 square miles. That is a huge! Manhattan itself is just under 23 square miles in size, and the research team concluded that neighborhood exposures would not have been fully captured if participants had merely reported their addresses and movement. The team also highlighted the utility of the GPS devices for understanding the movements of people who may not have stable housing and, therefore, no fixed home address, which was the case for nearly half of the study’s participants.
The research team took their geospatial analysis further by assessing how common it was for participants to visit neighborhoods prevalent with HIV. In the United States, transgender women have the highest HIV rates of almost any group, and so a geospatial understanding of the virus is particularly important. By linking participants’ movement data to publicly available data on HIV prevalence, the research team found that 58% of GPS coordinates were located in neighborhoods that, in New York City, have the highest prevalence of HIV.
Although the study authors were clear that their findings do not explain why HIV rates are so high among transgender women, they do hint at the potential relevance of considering neighborhood-level HIV prevalence. What this might mean, however, for HIV risk and prevention is difficult to say, especially because HIV rates in this study may have served as a proximal marker for the distribution of sexual and gender minority people in New York City more generally. Regardless, this study confirms the incredible value of using GPS to characterize neighborhood exposures, an approach that could prove useful in future research and public health efforts to reduce HIV and otherwise improve the health and well-being of transgender women.