There are a number of rules regarding spatial and temporal behavior that are demonstrated across this blog site. For a link to examples of particular subsets of skills, methodologies and applications, this page discusses the basic concepts of spatial disease or population health analysis, and provides links to how these concepts were applied as a part of my research. A number of examples of application for each of these methods are demonstrated, the reason this page was developed.
The following are some basic concepts I covered repeatedly during these different analyses over the years.
- Sequent Occupancy. This basic concept was in need of revival back in the late 1990s. At the time there was considerable resistance to my suggestion that this theory be applied to Medical Geography (thanks for enlightening me about it determinism history Rick). With time and application of this theory to other examples of disease processes, my certainty of its value in studying disease patterns solidified and according to the popularity of my pages on this topic, Sequent Occupancy is undergoing some sort of revival. My applications for sequent occupancy theory focus on medicine, disease and the relationship between poverty and health. The sequent occupancy theory can be used to differentiate disease patterns across space for a single point in time, historically or spatially, such as between neighboring areas. Both time and place are evaluated using sequent occupancy by reviewing what we can call the theory of social evolution theory, a neodarwinian concept. I have reviewed this topic on multiple pages (see the listing below for more).
- Hierarchical versus Non-hierarchical or linear-radial, and Reversed Hierarchical diffusion patterns. The work of Gordon Pyle helped define this concept in medical geography. I found a more concise application of it as a reversed hierarchical diffusion model as well, meaning that some diffusion processes take place from high to low hierarchical settings, whereas others like to follow the reverse order due to greater susceptibility of people in these preferred starting points. Studies of the different disease migration and diffusion processes add significantly to our understanding of disease flow patterns.
- Travel or Transportation Theory of Diffusion. This is a slightly different take on the above model, with transportation added as the primary feature used to define hierarchical processes. There is also a temporal component to this theory–different periods in time have different methods of travel. As a time-space feature, these human behaviors helped to define disease zones and reduce the natural limitations that once existed in older human population settings. This is perhaps the singlemost important human factor demonstrating an influence upon disease flow patterns.
- Topography and disease diffusion. The natural and human ecology of disease depends upon two major natural events or settings–the first is climate and weather, the second topography and the related biogeography of a given topographic region. A number of diseases I reviewed depend heavily upon topography when a diffusion process is initiated. Some of this influence relates to the method of diffusion or travel, such as by air versus water versus overland transportation route. Other times, topography has impacts upon very local climates and meteorological patterns. Either way, this is what made medical topography the first form of medical geography studied and practiced in United States history. It is also the key index word used to search for such articles in the older medical texts and journals.
- Latitude-Longitude specificity and disease diffusion. Due to the naming of the least healthy part of the earth’s surface as the “Torrid Zone” by Greek writers, weather, climate and latitude-longitude (but especially latitude) features play one of the most important roles in the early definitions of disease geography. A peak in this philosophy appears in the medical literature around 1800, when yellow fever became a global epidemic problem due to improvements in the transportation systems. Due to climate changes between the equator and the poles, the impacts of latitude on disease patterns are easier to comprehend. Longitudinal features exist as well, but usually due to conditions and changes that are purely topographic related, such as water edges and the formation of natural barriers by oceans and mountain ranges.
- World Regions, Regionalization, and Disease Patterns. With world travel came the knowledge of world disease patterns. These maps depict the conceptualization of these regional patterns diseases took on as the documentation of cultures from other parts of the world continued. The earliest impressions of region and health focused on climate, latitude, temperature, humidity and health. By 1800, regions where specific diseases existed were well-known, and consisted of diseases related to the region in general and diseases related to specific natural features of the region. The former often remained a part of the region’s history and was environmental in cause. The latter had the ability to be transferred by people and physical objects to other places, like Measles and the Pox, Syphilis, African tapeworm, Guinea worm, Chinese Tapeworm, Elephantiasis, Yaws, Dengue, Schistosomiasis, Ethiopian Leishmaniasis, Yellow Fever, and Asiatic cholera.
- Geosophy — the power of place in health and disease. The importance of place with regard to health resulted in the definition of the study of geosophy, from ‘knowing earth’ or ‘knowing place’. The modern take on geosophy relates to our very modern view of man as a responsible caregiver of the land, often linked to a number of cultural interpretations out there about living communally with nature (see wikipedia). This 1940s origin for geosophy is a by-product of a much longer tradition that man has had with nature. In the 1720s, a cartographer and geographer, Johanns Christopher Homann, decided to specialize on nature or natural geography and medicine, and for his dissertation combined the philosophy of medicine with that of geographers. As a result, he makes use of and describes the term Geosophem and its similar Geosophia. This represents the birth of geosophical thinking, at least in writing. There are a number of pages I have posted at this site centered on different places in local history, but since this site focuses on health and medicine, the pages most fit for review of Homann’s geosophy definition, at least for now, will rely upon much the same concepts as Homann’s Dissertation. Homann’s portrayal of the meaning of geosophy takes into account the teachings of Friedrich Hoffman (a chemist, plant pharmacist and naturalist) and Augustine Riverius. He evaluates the health of different places in the world and reviews how these health and disease issues relate to the local flora and its medicinal value. Homann’s work also focuses on endemic and epidemic disease geography. The same has been accomplished with my pages on this topic.
- Space-Time or the Space-Sociological (neo-darwinian) Evolution/Land use (pseudo-sequent occupancy) concept. When I reviewed the historical writings on the 1849 to 1853 cholera epidemic in the Americas, I noticed a recurring theme in the medical journal articles. There were often lower-income people attached to the initial cases, and it was through their travel from a port to a home in the low-income parts of the cities that led to the first cases for a given urban setting. This link between low-income and the unhealthy lifestyle of those in poverty recurs in rural settings as well as urban settings, like low-income housing set ups located along train tracks or crowded boarding houses and basement apartments in New York City. The best single examples of this are the tale about how the 1849-1852 cholera epidemic made its way to Kingston, Jamaica through a poor person residing in the outskirts of the city, and the means in which it came into part of New York City that same year by way of a crowded basement dwelling setting, occupied by underfed, poor Irishmen according to John C. Peters in his much later review of this disease (ca. 1880). The work of famous cholera epidemiologist John Snow and his associates mapping this disease along the Thames River came up with similar relationships between low-income living space and the initiation of a wave of cases within the various settings in and around London. My reversed hierarchical diffusion model was developed due to this theory.
- Sanitation and Disease. Important writers who were medical cartographers and/or epidemiologists linking sanitation to disease are Valentine Seaman (ca. 1800 for his New York Shipping Ports miasm), Samuel Mitchell (1800, for his septan), Scouttetten (1830-4 — the second European Asiatic cholera epidemic and first to come to the US), and John Lea, 1852 (the 3rd epidemic, 2d to US). Mitchell, Scouttetten and Lea were predecessors to what would later be called hygienists or sanitarians, who focused on “filth” in the form of naturally decaying debris and human garbage and waste as the cause for many epidemics.
- Timed Series Mapping. Timed series maps are those produced for multiple years that are displayed in consecutive order; they are not just a series of the past epidemics displayed in order but follow a specific time period. The periodic return of Asiatic cholera annually in and around Bangladesh enabled medical cartographers to analyze this disease trend over time in a way much more reliable than the yellow fever epidemics. Even though this use of the map was possible with yellow fever during the decades prior, this method of analysis was not regularly implemented and quite often the yellow fever was too irregular in its behaviors to enable effective timed series maps to be produced. The first decades of cholera (first two epidemics) consisted mostly of medical topography maps of the disease, for both small (city, town, neighborhood) and large regions (country, continent, globe). But due to its endemic nature at its point of origin, these regular returns could be mapped. From about 1854 onward, the review of timed series maps became a common practice for some parts of the world. These were provided in the form of annual or periodic reports submitted to government officials overseeing the work of the medical geographer and epidemiologist engage in this work. The examples shown here are the earliest British examples of such I have so far uncovered.
- Population Health and Disease mapping. Population and disease counts have long been part of the historical documentation kept by colonial and national governments. By 1790, it was common for some meteorological data to be kept as well, including temperature, wind flow and precipitation. By the end of the 1790s, this data was viewed with health and climate in mind, and in particular the behavior of specific endemic and epidemic disease patterns. Throughout the 1800s it was common to tabulate data yearly, quarterly and monthly regarding mortality rates and average life expectancy information for given regions. The develop of isopleth mapping as a means to demonstrate these important health statistics probably came about sometime in the early to mid-1800s, but wasn’t standardized enough for ongoing utilization until the late 1800s. This map is an early example of a population health map (more will be added when uncovered).
- The Shape of Space. Spatial analysis makes use of small areas, samples or analyzes these areas, and then projects this information onto much larger areas with the goal of defining relationships applicable to much larger areas. We routinely analyze space as an irregular area when we use governmental (country, state, county, township) boundaries, zip code tracts, population measurement regions (census blocks, block groups, tracts), and on occasion socio-political defined areas. With government derived base maps, we rarely employ perfect forms or shapes to our analyses, such as geospatially standardized circles, squares, or as I like to emphasize, hexagons. The traditional method employs subjective and culturally-defined methods to our analyses. The use of geospatially standardized methods like square (my CRI work) and hexagonal grids (CRIs), moving windows (west nile) and circles (CRIs), eliminates the subjectivity attached to boundaries and other human forms of localization and regionalization. It represents many of the same methods used to study population point-line-polygon relationships, but in a different order. We correct for irregularities in populations first, and then produce the final counts and statistics, instead of adjusting our final values. This is done not so much with the goal of making the methodology “better”, instead it served to make the numerical values more regular in their spatial distributions, thereby impacting the final isoline or isopleth images that can be produced with these results. My additional step of employing hexagons instead of squares serves to smooth these results even more, producing a more realistic cartographic impression of the final results based on contour or isoline mapping.
The links to each of these examples I covered are provided. At the end of each list is a series of symbols with links to modern video maps depicting related spatial epidemiological patterns for more recent disease diagnoses.
Derwent Stainthorpe Whittlesey, 1890-1910, and Alfred Meyer, 1950s-1960s
Hierarchical versus Non-hierarchical or linear-radial, and Reversed Hierarchical diffusion patterns
Reversed Hierarchical Diffusion
Cholera along the Mississippi, Judson, 1873 (popular at conferences)
Travel or Transportation Theory and Diffusion
Cholera along the Mississippi, Judson, 1873 (popular at conferences)
Topography and disease diffusion
Latitude-Longitude specificity and disease diffusion
World Regions, Regionalization and Regional Disease Patterns
Geosophy (the power of place in health and disease)
Space-Time, or the Space-Sociological (neo-Darwinian) Evolution/Land use (pseudo-sequent occupancy) concept
Sanitation and Disease
Investigating the Enteric Fever epidemics, 1873
Timed Series Mapping
Population Health and Disease mapping
The Shape of Space
3D, square cells