Spatial Dependence of Body Mass Index: Geneva, Switzerland

Urban health (UH) is an emerging field, which explores the effect of urban environment and urbanization on health. Evidence suggests that urban environment can either positively influence health behaviors or be a health stressor. One key approach in UH is the use of georeferenced data and geographic information system (GIS). Mapping disease prevalence and trends provide insight into disease mechanisms and etiologies. An important limitation of GIS is that data sets have likely been collected separately by different agencies, often over different time periods.The Canton of Geneva deviates from this limitation as it has been collecting geographic and health-related information continuously since 1998 through the Unit of Population Epidemiology (UEP) of the Geneva University Hospitals and its Bus Santé study. Combining health-related data from the Bus Santé study and GIS, using Local Indicators of Spatial Association (LISA), the investigators detected significant spatial dependance with respect to BMI. The results clearly indicate that BMI levels are not distributed at random in the Canton of Geneva. Moreover, performing preliminary exploratory analyses on blood pressure, investigators have identified cluster of individuals with higher blood pressure than the average, lifting up possible influences of environmental/urban factors (e.g., sidewalks, traffic, socioeconomic status).

A fine scale analysis of socio-economic and landscape variables for the assessment of health status in Geneva

Joël Chételat, Idris Guessous, Stéphane Joost, Abram Pointet

Significant differences in health status between inhabitants of different commune types of the Geneva area have recently been established in a study relying on a large health database managed by the Unit of Population Epidemiology of the Hôpitaux Universitaires de Genève (HUG). For instance, the mean Body Mass Index is lower in richer communes than in other urban areas. Moreover, suburban residents and commuting populations have a higher hypertension prevalence than other communities. Though socio-economic status appears to be an essential driver for quality of life and health, specific knowledge is lacking to define which variables are of main concern. Besides, the relationship between socio-economic conditions and neighbouring living environment is only implicit. The objective of the present study is to detail the spatial differences coarsely observed previously. More particularly, it aims to determine to which extent landscape indicators are related to health risk factors and to identify areas where prevalence of health risk factors is potentially high on a fine scale basis. The study reuses the “Bus santé” database containing health-related information for more than 10'000 participants collected since 1998.Stratified sampling by age and by gender was used for the survey to be representative of the population. Samples were geocoded so that they can be analysed in a Geographic Information System (GIS). The Geneva canton has been divided into some 1600 homogeneous zones called Microregions based on the number of inhabitants, jobs, buildings and dwellings. Demographic, socio-economic and landscape variables such as the proportion of built-in surface and volume or the Shannon land use diversity index inform each of the Microregions. Significant factors characterising them are identified using factor analysis in order to make a spatial typology. A multiple regression is applied to assess the relationship between a set of health variables (including blood pressure and hypertension, glucose level and diabetes) from the sampled individuals contained within the Microregions and the factors describing these. Results of this fine scale analysis show the importance of income and socio-cultural membership as primary variables related to lifestyle and potential health status. The chosen landscape composition and structure variables come as complementary explanatory factors of neighbourhood counting for well-being or on the contrary stress-related illness. As an environmental health research, this study directly contributes to address land planning issues and inform on how landscape design potentially impacts quality of life and population health. Moreover, it serves to identify spatial types where risk factors are high and locate them in the geographical space.

2012

Assessing environmental amenities and testing for discrimination in housing markets using hedonic price models

Caroline Schaerer

The present thesis applies the property hedonic price model in order to assess the economic value of environmental amenities and discrimination on the Swiss rental markets of Geneva and Zurich. Indeed, economic textbooks teach that differentials in environmental amenities are reflected in rent differentials, as are differentials in dwellings' size and quality. However, for the rents to be affected by environmental quality, the latter has to be perceived by the residents. Therefore, the use of perceived measures of environmental quality is recommended, although in practice most empirical applications use objective measures. In Chapter 2, we compare the use of scientific and perceived noise measures in a hedonic model and test whether the objective measure of road traffic noise is a good instrument to approximate the residents' perception of external noise on the Geneva rental market. We find convergent validity of the two measures for moderate to high noise levels. Then, in Chapter 3 the hedonic model is used to assess the value of natural land use and land use diversity in the urban regions of Geneva and Zurich. We make use of the geographic information system (GIS) to construct precise variables quantifying land uses and their patterns in the neighbourhoods of the buildings. We find that proximity to various environmental amenities as well as their size in the surrounding areas have a statistically significant impact on rents. Moreover, the estimated impacts are relatively similar in the two regions. The GIS capacities are used further in Chapter 4 in which we develop new and original three-dimensional variables for the Geneva rental market in order to quantify the view at the dwelling level. Including these view variables into a hedonic model shows that the view on various environmental amenities has a significant impact on rents. Moreover, dwellings with a view on the famous Geneva Jet d'eau and on the ancient cathedral are rented at a higher price. Finally, in Chapter 5, we account for the market imperfections of the housing markets and show how hedonic price equations could be used to reveal discrimination and prejudice. More specifically, we test whether some categories of households pay more than others for the same quality of housing and whether rents vary with the socio-economic composition of the neighbourhoods. We find evidence of discrimination against foreigners, particularly the less educated ones, on the rental markets of Geneva and Zurich. Moreover, we find that low education households, particularly those of foreign origin, live in dwellings of poorer quality. Then, we allow different household categories to face different marginal prices. We find evidence of discrimination in terms of living conditions based on nationality in the Geneva rental markets, while signs of discrimination in terms of living conditions appear against low education individuals in Zurich.

EPFL2008

Contribution du SIG à l'analyse des liens déchets-santé en milieu urbain dans les pays en développement

Sonwouignandé Kientga

Among the factors of health risks in urban areas, the solid and liquid wastes worsen particularly the problems of public health in developing countries. Uncontrolled solid waste disposal sites and waste water sites constitute major sources of danger for public health. Often, there is no mapped and documented inventory. The perception of danger related to infectious sources by the exposed populations is generally not well-known and even often ignored by the public institutions in their management policy of health and wastes. The same can be considered for the link between diagnosed diseases in health care services and the presence of waste disposal sites near patients' residences. The goal of this study is to determine the main factors of waste management and their consequences on health. This goal shall be reached using a GIS approach and through a case study concerning two districts in the town of Ouagadougou in Burkina Faso. In detail, the objectives are: i) to build a spatial database for waste disposal sites and public health care management and to propose a methodological approach for the elaboration of a GIS, associating social science, health and the geographical information science; ii) to identify and to analyze indicators of public health related to domestic and industrial waste; ii) to compare these indicators with the different actors' perception, according to the distance and dangers represented by the seriousness of potential danger sources; iv) to analyze if there is a relation between the actors' perception and the diseases diagnosed in health care services; v) to promote GIS in institutional structures in order to facilitate decision-making in waste management. Geographical information science has contributed to the creation of a database containing general geographical data, the disposal waste sites, the data of the actors' perception and health data. This database was used for spatial-thematic, temporal and statistical analyses. At first we have established an inventory of disposal waste sites. Hereafter we have analyzed their spatial influence. We then compared the situation to the perception of dangers and to the people's health risks, related to the distance to sources of potential danger. An analysis of the relation between the disease cases listed (counted) in health centers and the presence of waste (infectious) sources was carried out. This allowed some degree of comparison between the subjectivity of danger perception and the reality. The inventory of potential danger sources and the analysis of their influence spheres shows that 86 % (456 ha) of the study area is threatened by a danger, among which 45 % (235 ha) are considered exposed to a higher danger. The results also show that only 14 % of the population in both sectors (2'574 inhabitants of 18'978 total inhabitants) is not exposed to potential health risks. The analysis of the perceived danger according to the distance revealed that the perceived danger generally decreases proportionally to the distance. Surprisingly certain persons living near a polluted site don't consider the site as dangerous. However others, living far away from the same site, perceive it as dangerous. In these cases the subjective dimension of the perception is thus revealed. The temporal analyses of listed diseases show a correlation between the cases of malaria and the precipitation. The time gap between precipitation-related peaks and malaria cases related peaks varies from two to three months, leaving enough time to take preventive measures. We were not able to establish a link between the patient's residence and pollution sources; because the patient's geographical location is not mentioned in the health care services' registers. A modification of the registration forms has been suggested. The developed methodology and the results gathered led to the establishment of suggestions and recommendations based on the integration of GIS in waste and health management. This study has already contributed to the setup of a geo-information network composed of various actors in waste and health management.

EPFL2008

Contribution du SIG à l'analyse des liens déchets-santé en milieu urbain dans les pays en développement

Sonwouignandé Kientga

EPFL2008

Assessing environmental amenities and testing for discrimination in housing markets using hedonic price models

Caroline Schaerer

EPFL2008

A fine scale analysis of socio-economic and landscape variables for the assessment of health status in Geneva

Joël Chételat, Idris Guessous, Stéphane Joost, Abram Pointet

2012