Measuring social inequalities in cause-specific mortality in France: comparison between linked and unlinked approaches.

BACKGROUND: Monitoring the time trends in socioeconomic inequalities in mortality by cause is a key public health issue. The aim of this study was to compare methods to measure social inequalities in cause-specific mortality in the French population aged 25-55 years. More specifically, it compares bias and precision related to the use of occupational class declared at the last census (linked data) to the one declared at the time of death on the death certificate (unlinked data). METHODS: We used a representative sample of 1% of the French population. Causes of death were obtained by direct linkage with the French national death registry. Occupational class was classified into eight categories. Taking professionals and managers as the reference, relative risks of mortality by cause and their 95% confidence intervals were estimated using Poisson models for the 1983-1989, 1991-1997, and 2000-2006 periods. The relative risks were calculated with both linked data and exhaustive unlinked data. RESULTS: Over the 2000-2006 period, occupational classes declared at census and on the death certificate were consistent for half of the deaths. Relative risks for manual workers were found to be similar between the two approaches over the 1983-1989 and 1991-1997 periods, and higher for the unlinked approach over the 2000-2006 period. Over the latter period, the order and magnitude of relative risks varied similarly by occupational class and cause of death for both approaches. Confidence intervals obtained from linked data were wide. CONCLUSION: Occupational class derived from the death certificate must be used with caution as a measure for epidemiological purposes and the available linked data do not allow accurate estimates of social inequalities in cause-specific mortality. Other solutions should be considered in order to improve the follow-up of social inequalities in mortality. This would require the collection of educational level on the death certificate or the linkage of the cause of death database with other exhaustive and informative databases.

Low exposure to sunlight is a risk factor for Crohn's disease.

BACKGROUND: Low sunshine exposure might contribute to the pathogenesis of inflammatory bowel disease (IBD). AIM: To assess the geographic distribution of IBD incidence in relation to sunshine exposure in France to test the hypothesis that higher sun exposure is associated with lower IBD risk. METHODS: Using the national health insurance database, incidence rates of Crohn's disease (CD) and ulcerative colitis (UC) were estimated for each of the 94 French administrative areas ('départements'), between 2000 and 2002. The surface UV radiation intensity was obtained by combining modelling and satellite data from Meteosat, the European meteorological satellite. Relationships between incidence rates and sun exposure were tested for significance by using a Poisson regression. We mapped smoothed relative risks (sRR) for CD and UC, using a Bayesian approach and adjusting for sun exposure, to search for geographical variations. RESULTS: Areas with a smoothed RR of CD incidence significantly above 1 corresponded to areas with low sunshine exposure, whereas those with high or medium sunlight exposure had smoothed RRs either lower than 1 or not significantly different from 1. There was no association between sun exposure and UC incidence. CONCLUSIONS: This geographic study suggests that low sunlight exposure is associated with an increased incidence of Crohn's disease. Further studies are needed to determine if this association is causal.

[Geographic differences of bronchopulmonary cancer mortality in France and spatial scales of analysis: significance of scale change in health geography]. / Disparités géographiques de mortalité par cancers broncho-pulmonaires en France et échelles spatiales d'analyse: intérêt du changement d'échelle en géographie de la santé.

BACKGROUND: It is important to choose a valid spatial scale to study health differences in a geographical perspective. Many scales can be valid and a combination is required to understand the spatial distribution of a given health problem. Geographic distribution of lung cancer was studied in France using different scales to illustrate the importance of changing scales in health geography. METHODS: Standardized rates (direct method) for lung cancer were calculated for the period 1988-92 and mapped at different scales. RESULTS: Original spatial structure was observed for each scale. This proved that different interactions occur at each scale between environmental and social factors. Changing the scale allowed a better understanding of variations in the spatial distribution of lung cancer. CONCLUSIONS: The validity of a regional scale to study health geographical distributions is questioned. Changing the scale would allow proposing action to improve health promotion.

[Cartography of epidemiologic data. The principal methods of making continuous data discrete and their importance in cartographic representation]. / La cartographie des données épidémiologiques. Les principales méthodes de discrétisation et leur importance dans la représentation cartographique.

The cartographic representation of continuous quantitative data is often required in studies of the spatial distribution of health indicators. It imposes a succession of choices which directly affect the result obtained. The conversion of continuous data to discrete data is one of the most important steps in the development of epidemiological maps. This article presents the methods currently used to make data discrete, discusses the advantages and disadvantages of each method and assesses their appropriateness for various situations. As an example, and for comparison purposes, we mapped the same series of statistics (relative rates of avoidable male deaths, "associated with the health care system", for "employment zones" in France from 1988 to 1992), using each of the methods discussed.

Mapping epidemiological results. The principles behind methods to make continuous data discrete and their importance in cartographic representation

The cartographic representation of continuous quantitative data is often required in studies of the spatial distribution of health indicators. It imposes a succession of choices which directly affect the result obtained. The conversion of continuous data to discrete data is one of the most important steps in the development of epidemiological maps. This article presents the methods currently used to make data discrete, discusses the advantages and disadvantages of each method and assesses their appropriateness for various situations. As an example, and for comparison purposes, we mapped the same series of statistics (relative rates of avoidable male deaths, "associated with the health care system", for "employment zones" in France from 1988 to 1992), using each of the methods discussed.