Paul L. Delamater

Measuring geographic access to health care: raster and network-based methods

BackgroundInequalities in geographic access to health care result from the configuration of facilities, population distribution, and the transportation infrastructure. In recent accessibility studies, the traditional distance measure (Euclidean) has been replaced with more plausible measures such as travel distance or time. Both network and raster-based methods are often utilized for estimating travel time in a Geographic Information System. Therefore, exploring the differences in the underlying data models and associated methods and their impact on geographic accessibility estimates is warranted.MethodsWe examine the assumptions present in population-based travel time models. Conceptual and practical differences between raster and network data models are reviewed, along with methodological implications for service area estimates. Our case study investigates Limited Access Areas defined by Michigan’s Certificate of Need (CON) Program. Geographic accessibility is calculated by identifying the number of people residing more than 30 minutes from an acute care hospital. Both network and raster-based methods are implemented and their results are compared. We also examine sensitivity to changes in travel speed settings and population assignment.ResultsIn both methods, the areas identified as having limited accessibility were similar in their location, configuration, and shape. However, the number of people identified as having limited accessibility varied substantially between methods. Over all permutations, the raster-based method identified more area and people with limited accessibility. The raster-based method was more sensitive to travel speed settings, while the network-based method was more sensitive to the specific population assignment method employed in Michigan.ConclusionsDifferences between the underlying data models help to explain the variation in results between raster and network-based methods. Considering that the choice of data model/method may substantially alter the outcomes of a geographic accessibility analysis, we advise researchers to use caution in model selection. For policy, we recommend that Michigan adopt the network-based method or reevaluate the travel speed assignment rule in the raster-based method. Additionally, we recommend that the state revisit the population assignment method.

Spatial accessibility in suboptimally configured health care systems: A modified two-step floating catchment area (M2SFCA) metric

The floating catchment area (FCA) family of metrics employ principles from gravity-based models to incorporate supply, demand, and distance in their characterization of the spatial accessibility of health care resources. Unlike traditional gravity models, the FCA metrics provide an output in highly interpretable container-like units (e.g., physicians per person). This work explores two significant issues related to FCA metrics. First, the Three Step Floating Catchment Area is critically examined. Next, the research shows that all FCA metrics contain an underlying assumption that supply locations are optimally configured to meet the needs of the population within the system. Because truly optimal configurations are highly unlikely in real-world health care systems, a modified two-step floating catchment area (M2SFCA) metric is offered to address this issue. The M2SFCA is built upon previous FCA metrics, but allows for spatial accessibility to be discounted as a result of the suboptimal configuration of health care facilities within the system. The utility of the new metric is demonstrated through simulated data examples and a case study exploring acute care hospitals in Michigan.

The Measles Vaccination Narrative in Twitter: A Quantitative Analysis

Background The emergence of social media is providing an alternative avenue for information exchange and opinion formation on health-related issues. Collective discourse in such media leads to the formation of a complex narrative, conveying public views and perceptions. Objective This paper presents a study of Twitter narrative regarding vaccination in the aftermath of the 2015 measles outbreak, both in terms of its cyber and physical characteristics. We aimed to contribute to the analysis of the data, as well as presenting a quantitative interdisciplinary approach to analyze such open-source data in the context of health narratives. Methods We collected 669,136 tweets referring to vaccination from February 1 to March 9, 2015. These tweets were analyzed to identify key terms, connections among such terms, retweet patterns, the structure of the narrative, and connections to the geographical space. Results The data analysis captures the anatomy of the themes and relations that make up the discussion about vaccination in Twitter. The results highlight the higher impact of stories contributed by news organizations compared to direct tweets by health organizations in communicating health-related information. They also capture the structure of the antivaccination narrative and its terms of reference. Analysis also revealed the relationship between community engagement in Twitter and state policies regarding child vaccination. Residents of Vermont and Oregon, the two states with the highest rates of non-medical exemption from school-entry vaccines nationwide, are leading the social media discussion in terms of participation. Conclusions The interdisciplinary study of health-related debates in social media across the cyber-physical debate nexus leads to a greater understanding of public concerns, views, and responses to health-related issues. Further coalescing such capabilities shows promise towards advancing health communication, thus supporting the design of more effective strategies that take into account the complex and evolving public views of health issues.

An analysis of asthma hospitalizations, air pollution, and weather conditions in Los Angeles County, California

There is now a large body of literature supporting a linkage between exposure to air pollutants and asthma morbidity. However, the extent and significance of this relationship varies considerably between pollutants, location, scale of analysis, and analysis methods. Our primary goal is to evaluate the relationship between asthma hospitalizations, levels of ambient air pollution, and weather conditions in Los Angeles (LA) County, California, an area with a historical record of heavy air pollution. County-wide measures of carbon monoxide (CO), nitrogen dioxide (NO(2)), ozone (O(3)), particulate matter<10 μm (PM(10)), particulate matter<2.5 μm (PM(2.5)), maximum temperature, and relative humidity were collected for all months from 2001 to 2008. We then related these variables to monthly asthma hospitalization rates using Bayesian regression models with temporal random effects. We evaluated model performance using a goodness of fit criterion and predictive ability. Asthma hospitalization rates in LA County decreased between 2001 and 2008. Traffic-related pollutants, CO and NO(2), were significant and positively correlated with asthma hospitalizations. PM(2.5) also had a positive, significant association with asthma hospitalizations. PM(10), relative humidity, and maximum temperature produced mixed results, whereas O(3) was non-significant in all models. Inclusion of temporal random effects satisfies statistical model assumptions, improves model fit, and yields increased predictive accuracy and precision compared to their non-temporal counterparts. Generally, pollution levels and asthma hospitalizations decreased during the 9 year study period. Our findings also indicate that after accounting for seasonality in the data, asthma hospitalization rate has a significant positive relationship with ambient levels of CO, NO(2), and PM(2.5).

Defoliation and the war on drugs in Putumayo, Colombia

Analysis of three Landsat Enhanced Thematic Mapper Plus (ETM+) images of the Putumayo region of Colombia, one of the primary regions of coca production in Colombia, demonstrated that aerial spraying of defoliants under the US ‘Plan Colombia’ programme impacted broad swaths of the landscape and had the unintended consequence of defoliating contiguous and interspersed native plant and food crop parcels. Using fractional coverage, field data collections and a hybrid classification, 106 178 ha of impacted land were found, compared with the United Nations Drug Control Program reported reduction in coca of 71 891 ha, an unexplained difference of 34 287 ha. The complex spatial organization of the Colombian coca‐producing landscape appeared to confound the spraying of defoliants, and as demonstrated here, many non‐coca land cover classes have been affected adversely.

Sociodemographic Predictors of Vaccination Exemptions on the Basis of Personal Belief in California

OBJECTIVES We examined the variability in the percentage of students with personal belief exemptions (PBEs) from mandatory vaccinations in California schools and communities according to income, education, race, and school characteristics. METHODS We used spatial lag models to analyze 2007-2013 PBE data from the California Department of Public Health. The analyses included school- and regional-level models, and separately examined the percentage of students with exemptions in 2013 and the change in percentages over time. RESULTS The percentage of students with PBEs doubled from 2007 to 2013, from 1.54% to 3.06%. Across all models, higher median household income and higher percentage of White race in the population, but not educational attainment, significantly predicted higher percentages of students with PBEs in 2013. Higher income, White population, and private school type significantly predicted greater increases in exemptions from 2007 to 2013, whereas higher educational attainment was associated with smaller increases. CONCLUSIONS Personal belief exemptions are more common in areas with a higher percentage of White race and higher income.

Lessons from the Ebola Outbreak: Action Items for Emerging Infectious Disease Preparedness and Response

As the Ebola outbreak in West Africa wanes, it is time for the international scientific community to reflect on how to improve the detection of and coordinated response to future epidemics. Our interdisciplinary team identified key lessons learned from the Ebola outbreak that can be clustered into three areas: environmental conditions related to early warning systems, host characteristics related to public health, and agent issues that can be addressed through the laboratory sciences. In particular, we need to increase zoonotic surveillance activities, implement more effective ecological health interventions, expand prediction modeling, support medical and public health systems in order to improve local and international responses to epidemics, improve risk communication, better understand the role of social media in outbreak awareness and response, produce better diagnostic tools, create better therapeutic medications, and design better vaccines. This list highlights research priorities and policy actions the global community can take now to be better prepared for future emerging infectious disease outbreaks that threaten global public health and security.

Assessing the spatial accessibility of hospital care in Sichuan Province, China

Regional disparities in geographical access to hospital care are found throughout China. Understanding variations in the spatial accessibility of hospital care has the potential to provide decision support in healthcare planning. This study examines the hospital system in the Sichuan Province in China, which provides healthcare for more than 80 million people. We examine the impacts of accessibility characterisation via the conventional measurement approach by comparing the results to those derived using a floating catchment area approach. Employing a geographical information system based on population and hospital administrative data, we conducted a province-wide study of the spatial accessibility of hospital care in Sichuan Province, China. A shortest-path analysis and the enhanced two-step floating catchment area (E2SFCA) method were implemented. Substantial differences between these two approaches were found, including a roughly 15% difference in the total number of under-served areas. Generally, spatial accessibility was higher in the eastern regions of Sichuan. More than 5.5 million people were found to have limited access, with large variations across the province. These results indicate that the official method used by policy makers in China may not capture the true nature of spatial accessibility throughout the region. We recommend that the E2SFCA method be implemented for health services research in China, providing decision makers with more accurate information when setting healthcare policies.

Change in Medical Exemptions From Immunization in California After Elimination of Personal Belief Exemptions

Change in Medical Exemptions From Immunization in California After Elimination of Personal Belief Exemptions California Senate bill (SB) 277 eliminated the personal belief exemption (PBE) provision from the state’s school-entry vaccine mandates prior to the 2016-2017 school year. Previously, vaccine-hesitant parents could acquire a PBE for their child based on philosophical or religious beliefs. Now, the only pathway for an unvaccinated kindergartener to enter a public or private school in California is with a medical exemption (ME), which requires a written statement from a licensed physician describing the medical reasons that immunization is unsafe.1 Previously, MEs were only granted to children with a contraindication to vaccination; however, SB 277 gave physicians broader discretion to grant MEs for reasons other than a contraindication, including family medical history.2,3 One concern voiced after the passage of SB 277 was whether vaccine-hesitant parents would seek MEs as replacements for PBEs and would find physicians willing to oblige them.4 We evaluated the statewide change in MEs in the first year under SB 277 and whether MEs increased in regions with high PBE use prior to its enactment. Methods | We used publicly available data from the California Department of Public Health’s yearly Kindergarten Immunization Assessment reports. Each year, all schools are required to submit kindergarten enrollment, vaccination, and exemption data; more than 95% of all kindergarteners are represented in the yearly reports, which include statewide and county-level data. We extracted the statewide ME and PBE percentages for incoming kindergarteners from 1996 to 2016. We calculated and mapped the 1-year change in ME percentage (2015 to 2016) for counties and used Pearson correlation to test whether county-level change in ME percentage was associated with PBE use in the year prior to the implementation of SB 277. We used ArcGIS (Esri), version 10.3, for mapping and R (R Foundation), version 3.3.2, for the correlation test.

California Senate Bill 277’s Grandfather Clause and Nonmedical Vaccine Exemptions in California, 2015-2022

California Senate Bill 277’s Grandfather Clause and Nonmedical Vaccine Exemptions in California, 2015-2022 On June 25, 2015, California’s governor approved Senate Bill (SB) 277, a state law that substantially narrows exceptions to school-entry vaccination mandates. The law goes into effect on July 1, 2016, and California will join Mississippi and West Virginia as the third state to disallow nonmedical exemptions (NMEs) from vaccination based on religious or philosophical beliefs for students entering public or private schools.1 Only medical exemptions will be permitted. In a compromise during the legislative process in May 2015, the SB 277 authors included a “grandfather clause” that allows students who already possess an NME to continue attending school without vaccination until their next vaccination grade checkpoint (seventh grade in California).2 Although the decision to grandfather students with a pre–SB 277 NME reduces the potential for conflict between schools and vaccine-hesitant parents, it also allows students with NMEs to remain within California’s schools in the near future. We provide, to our knowledge, the first detailed estimates of the effects of SB 277’s grandfather clause on NMEs in California’s schools.