Anthony C. Gatrell

Spatial point pattern analysis and its application in geographical epidemiology

This paper reviews a number of methods for the exploration and modelling of spatial point patterns with particular reference to geographical epidemiology (the geographical incidence of disease). Such methods go well beyond the conventional ‘nearest-neighbour’ and ‘quadrat’ analyses which have little to offer in an epidemiological context because they fail to allow for spatial variation in population density. Correction for this is essential if the aim is to assess the evidence for ‘clustering’ of cases of disease. We examine methods for exploring spatial variation in disease risk, spatial and space-time clustering, and we consider methods for modelling the raised incidence of disease around suspected point sources of pollution. All methods are illustrated by reference to recent case studies including child cancer incidence, Burkitt’s lymphoma, cancer of the larynx and childhood asthma. An Appendix considers a range of possible software environments within which to apply these methods. The links to modern geographical information systems are discussed.

GIS and health

Methodological Issues. GIS and Health Research: An Introduction. GIS as an Enabling Technology. Spatial Statistics and the Analysis of Health Data. Statistical Methods for Spatial Epidemiology: Tests for Randomness. Improving the Geographic Basis of Health Surveillance Using GIS. Modelling Spatial Variations in Air Quality Using GIS. GIS, Time Geography and Health. Applications. GIS Applications for Environment and Health in Italy. A Multipurpose Interactive Mortality Atlas of Italy.

Complexity theory and geographies of health: a critical assessment

Abstract The interest of social scientists in complexity theory has developed rapidly in recent years. Here, I consider briefly the primary characteristics of complexity theory, with particular emphasis given to relations and networks, non-linearity, emergence, and hybrids. I assess the ‘added value’ compared with other, existing perspectives that emphasise relationality and connectedness. I also consider the philosophical underpinnings of complexity theory and its reliance on metaphor. As a vehicle for moving away from reductionist accounts, complexity theory potentially has much to say to those interested in research on health inequalities, spatial diffusion, emerging and resurgent infections, and risk. These and other applications in health geography that have invoked complexity theory are examined in the paper. Finally, I consider some of the missing elements in complexity theory and argue that while it is refreshing to see a fruitful line of theoretical debate in health geography, we need good empirical work to illuminate it.

Interactive spatial data analysis in medical geography

Interactive spatial data analysis involves the use of software environments that permit the visualization, exploration and, perhaps, modelling of geographically-referenced data. Such systems are of obvious value in epidemiological research, both of an environmental and geographical nature. There is an increasing number of such software environments available on a variety of platforms and operating systems. This paper considers the use of the proprietary Geographical Information System, ARC/INFO, in a spatial analysis context, showing how the spatial analytic tools that may be added to it can be exploited by geographical epidemiologists; such tools include those for modelling possible raised incidence of disease around suspected sources of pollution. The paper also reviews the use of systems such as S-Plus and XLISP-STAT, statistical programming environments to which spatial analysis functions or libraries may be added. The use of INFO-MAP, a system designed to aid in the teaching of interactive spatial data analysis, is also highlighted. The various software environments are illustrated with reference to examples concerned with: clustering of childhood leukaemia in part of Lancashire, England; Burkitts lymphoma in Uganda; larynx cancer in Lancashire; and childhood mortality in Auckland, New Zealand.

Involvement of deprivation and environmental lead in neural tube defects: a matched case-control study

OBJECTIVE To analyse the prevalence of neural tube defects in small geographical areas and seek to explain any spatial variations with reference to environmental lead and deprivation. SETTING The Fylde of Lancashire in the north west of England. DESIGN Cases were ascertained as part of a prospective survey of major congenital malformations in babies born in the Fylde to residents there between 1957 and 1981. A matched case-control analysis used infants with cardiovascular system, alimentary tract, and urinary system malformations as controls. Conditional logistic regression was used to assess the effects of more than 10 μg/l lead in drinking water and the Townsend deprivation score. RESULTS The prevalence of neural tube defects in 1957–73 was higher in Blackpool, Fleetwood, and North Fylde, whereas the three control groups showed no significant spatial variation. In 1957–81 mothers living in electoral wards with either a higher proportion of houses with more than 10 μg/l lead in the water or a higher deprivation score had a greater risk of having a baby with a neural tube defect. For spina bifida and cranium bifidum alone, this was also true. For anencephaly, deprivation was less important although the effect of lead was still seen. In some neural tube defects, lead may act independently of other possible factors associated with deprivation. It seemed unlikely that lead levels changed significantly during the survey. The percentage of houses with 10 μg/l or more of lead in the water in 1984–5 was similar to that found in Great Britain 10 years previously. CONCLUSION There is evidence to suggest that lead is one cause of neural tube defects, especially anencephaly. This could link the known preventive actions of hard water and folic acid. Calcium is a toxicological antagonist of lead. One cause of a deficiency of folic acid is impaired absorption secondary to zinc deficiency, which may be produced or exacerbated by lead.

On the spatial representation and accuracy of address-based data in the United Kingdom

Abstract A major task in applications of geographical information systems is to translate from address codes to grid references. In the United Kingdom this is commonly accomplished using the Central Postcode Directory (CPD), which allows conversion of postcodes to Ordnance Survey grid references. A commercial company, Pinpoint Analysis Ltd, is currently digitizing all properties and attaching postcodes. The paper assesses the accuracy of CPD data compared with Pinpoint data, especially in terms of how the grid references in the two cases relate to the boundaries of enumeration districts (EDs). Results from a small-scale study in Cumbria suggest that nearly 40 per cent of postcodes from the CPD file may be misallocated to EDs.

The relationship between socio-demographic characteristics and dental health knowledge and attitudes of parents with young children.

Objective To determine if parental socio-demographic characteristics are associated with dental knowledge and attitude.Design A questionnaire survey of 500 consecutive parents with children aged approximately 8-months, attending clinics in 1999/2000, in Burnley, Pendle and Rossendale, for health visitor distraction-hearing tests.Outcome measures Scores were obtained for dental knowledge and attitudes. The socio-demographic variables of parental ethnicity, age, education and area of residence were used to determine any associations.Results Parental age ranged between 16–46 years. Child age ranged between 7–11 months. Significant differences were detected for parental dental knowledge according to ethnicity (P = 0.003), educational status (P = 0.000), and area of residence (P = 0.016). Significant differences were also found in dental attitudes; ethnicity (P = 0.000), educational status (P = 0.004) and area of residence (P = 0.005). Parental age was not significant for either knowledge or attitude.Conclusions Lack of further education, being Asian and living in a deprived area means parents have less chances of high dental knowledge and positive dental attitudes.

Do area-level population change, deprivation and variations in deprivation affect individual-level self-reported limiting long-term illness?

A previous study showed that variations in deprivation within small localities in England and Wales influenced the rates of self-reported limiting long-term illness, controlling for overall levels of deprivation. These results suggest that while morbidity is related to overall levels of material deprivation, the distribution of resources within small areas have a significant effect on health outcomes. However, it is possible that these area effects become redundant once individual-level characteristics are accounted for. This analysis examines whether area-level deprivation and variations in deprivation are significant indicators of individual-level limiting long-term illness, once individual characteristics have been accounted for.

The Relative Utility of the Central Postcode Directory and Pinpoint Address Code in Applications of Geographical Information Systems

Considerable use is made of postcoded data in GIS (geographical information system) research. This is especially true of applications in geodemographics and epidemiology, but the work described here is of relevance in any attempt to attach specific locational identifiers to unit postcodes in Britain. Conventionally, unit postcodes are given an explicit spatial reference by means of the Central Postcode Directory (CPD), in which 100-metre grid references are assigned to each postcode. However, in a major undertaking, the company Pinpoint Analysis Ltd is digitising every property, both domestic and commercial, in the country. This gives a 1 metre grid reference for each such property; from the set of all addresses in a unit postcode a centroid may be obtained. In this paper the locational referencing provided by the ‘Pinpoint Address Code’ is compared with that of the CPD. The empirical work draws on data for Camden in London, but reference is made to earlier work in Whitehaven. We make some observations on the value of using point data in GIS (notably epidemiological) research, rather than relying on data for essentially arbitrary areal units.

Mortality from amyotrophic lateral sclerosis in Finland, 1986-1995

Objective– To study the possible changes, between 1986 and 1995, in the mortality due to amyotrophic lateral sclerosis (ALS) among Finnish patients. Materials and methods– A total of 1000 deaths from ALS were extracted from the Finnish Death Certificate Register for the study years. General population data were obtained from the Statistical Yearbooks of Finland. Results– From a death rate of 1.54/100,000 in 1986 an increase to 2.27/100,000 in 1995 was observed. Since 1963 the number of ALS deaths has tripled. The documented increased life‐expectancy in Finland correlates with the ALS death rate, at least partly explaining the increase. Contrary to other countries, on the whole equal numbers of men and women died of ALS. Women tended to be older than men when they died of ALS. Conclusion– In accordance with other countries ALS mortality in Finland is steadily increasing.