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A New Clustering Method for Time Series to Discover Geographical Cancer Trends from 1960 to 2000
744
ABSTRACTS (ACE)
AEP Vol. 17, No. 9 September 2007 : 723–751
P60 A NEW CLUSTERING METHOD FOR TIME SERIES TO DISCOVER GEOGRAPHICAL CANCER TRENDS FROM 1960 TO 2000 M Gettler Summa, (Department of Applied Mathematics, Universite´ Paris Dauphine, France); JM Steyaert, (Department of Computer Science, EcolePolytechnique, Paris, France); F Vautrain, (Department of Statistics, Isthma, France); R Weitkunat, (Department of Epidemiology and Statistics, Philip Morris International, Switzerland) PURPOSE: The research aims at finding a typology of 32 countries over 41 years, 1960–2000 and 52 countries over 21 years, 1980–2000 by an automatic comparative treatment of their cancer mortality time series. METHODS: To extract knowledge from the databases we have been using recent original results in Complex Functional Multivariate Data Mining. The result of the hierarchy proposes an order on the terminal nodes that optimizes the distances, according to the initial dissimilarity matrix. We considered initially 122 countries from the World Health Organization time series data, both sexes, 21 age-classes: 53% had missing data and 5% had out of the range figures. We had to reconstruct a common cancer denomination since the International Classification of Diseases varies over the years. We have thus taken into account the 9th ICD, from 1979 to 1998, and then the 10th.We had to compute normalized figures: the Standardized Age Ratios deal with 5 years age-classes and the reference population is the Segi one. RESULTS: As an example of the results, eight groups were finally retained for the trend typology of ‘all cancers’ on the 32 countries, and eleven groups on the 52 countries. They have been displayed on a world map and characterized in terms of levels and variations of cancer mortality. A second result is the stability of groupings for the countries which appear in both periods. For the ‘western style’ countries, a major result is that the paragons of the curve clusters tend towards an interval of values much smaller in 2000 than twenty years before. CONCLUSION: The functional multivariate pyramidal clustering of time series proved to be efficient and revealed underlying and interpretable clusters among cancer evolutions across countries in the past forty years. doi: 10.1016/j.annepidem.2007.07.064
P61 CONFOUNDING OF INDIRECT EFFECTS IN THE ‘‘REAL WORLD’’: EXPLORING THE RANGE OF BIAS DUE TO A COMMON CAUSE OF THE MEDIATOR AND OUTCOME D Hafeman, Columbia University Several investigators have demonstrated that assessment of indirect effects is biased in the presence of a common cause of the intermediate variable and the outcome. However, little work has been done to determine the degree of bias that will be caused by this type of confounding, and whether this bias will materially affect the identification of indirect effects. To address this crucial question, we have developed simulations based on a sufficient-component cause model for mediation. Confounding of the mediator can be
introduced into such a model by specifying a common component cause of the intermediate variable and the outcome. By testing a range of prevalence proportions for each independent component cause, we vary both mediational effects and the strength of confounding. These simulations are designed to yield both (1) the true indirect effect of interest (pure and/or total indirect effect) and (2) the observed indirect effect. A comparison of these values indicates the range of bias due to uncontrolled confounding of the intermediate variable. Simulation techniques will be applied to a motivating example from the Health Effects of Arsenic Longitudinal Study. In this example, arsenic exposure is associated with mortality, and the investigators hypothesize that this association is at least partially mediated through skin lesions. Based on known prevalences and strengths of association, simulations will be developed to assess the degree to which inference regarding this hypothesis might be biased. doi: 10.1016/j.annepidem.2007.07.065
P62 THE LEGACY OF THE TUSKEGEE SYPHILIS STUDY: ITS IMPACT ON WILLINGNESS TO PARTICIPATE IN BIOMEDICAL STUDIES RV Katz, BL Green, NR Kressin, SS Kegeles, MQ Wang, SA James, SL Russell, C Claudio, JM McCallum, Department of Epidemiology & Health Promotion, NYU College of Dentistry PURPOSE: The origins of the phrase ‘legacy of the Tuskegee Syphilis Study (TSS)’ lie in the widely held belief that Blacks are more reluctant than Whites to participate in biomedical research studies because of that infamous study. This paper is the first to address the validity of the ‘legacy’, a key issue in subject recruitment, in a multi-city, multi-racial, large-scale random survey using a detailed questionnaire. METHODS: The Tuskegee Legacy Project (TLP) Questionnaire, which contains two validated scales, the Likelihood of Participation (LOP) Scale and the Guinea Pig Fear Factor (GPFF) Scale, was administered via random-digit dial telephone interviews to respondents aged 18 years and older in three U.S. cities: Tuskegee, AL; Birmingham, AL; and Hartford, CT. Awareness of the TSS was measured as a yes/no response to two separate questions asking if they had ‘ever heard of the TSS’ while detailed knowledge of the TSS was assessed by a set of seven questions. RESULTS: Response rates, by city, ranged from 49–70% and yielded 327 Black and 499 White respondents. Awareness of the Tuskegee Syphilis Study was significantly higher in Blacks than Whites within each city, and ranged from a high of 93.3% for Blacks in Tuskegee, AL, to a low of 41.9% for Whites in Hartford, CT. While adjusted analyses (age, sex, education and income) revealed no association (p !0.05) between either general awareness or detailed knowledge of the Tuskegee Syphilis Study and willingness to participate (LOP Scale) in biomedical research either for Blacks or Whites, Blacks did show an direct association (pZ0.02) between awareness and increased GPFF scores, indicating increased wariness. CONCLUSION: As these data show no association between awareness of TSS and willingness to participate (albeit in Blacks, awareness was associated with an increased wariness), the longheld belief about the ‘legacy’ of the Tuskegee Syphilis Study that Blacks would be less willing to participate in biomedical studies is not supported by this study. doi: 10.1016/j.annepidem.2007.07.066
ABSTRACTS (ACE)
AEP Vol. 17, No. 9 September 2007 : 723–751
P60 A NEW CLUSTERING METHOD FOR TIME SERIES TO DISCOVER GEOGRAPHICAL CANCER TRENDS FROM 1960 TO 2000 M Gettler Summa, (Department of Applied Mathematics, Universite´ Paris Dauphine, France); JM Steyaert, (Department of Computer Science, EcolePolytechnique, Paris, France); F Vautrain, (Department of Statistics, Isthma, France); R Weitkunat, (Department of Epidemiology and Statistics, Philip Morris International, Switzerland) PURPOSE: The research aims at finding a typology of 32 countries over 41 years, 1960–2000 and 52 countries over 21 years, 1980–2000 by an automatic comparative treatment of their cancer mortality time series. METHODS: To extract knowledge from the databases we have been using recent original results in Complex Functional Multivariate Data Mining. The result of the hierarchy proposes an order on the terminal nodes that optimizes the distances, according to the initial dissimilarity matrix. We considered initially 122 countries from the World Health Organization time series data, both sexes, 21 age-classes: 53% had missing data and 5% had out of the range figures. We had to reconstruct a common cancer denomination since the International Classification of Diseases varies over the years. We have thus taken into account the 9th ICD, from 1979 to 1998, and then the 10th.We had to compute normalized figures: the Standardized Age Ratios deal with 5 years age-classes and the reference population is the Segi one. RESULTS: As an example of the results, eight groups were finally retained for the trend typology of ‘all cancers’ on the 32 countries, and eleven groups on the 52 countries. They have been displayed on a world map and characterized in terms of levels and variations of cancer mortality. A second result is the stability of groupings for the countries which appear in both periods. For the ‘western style’ countries, a major result is that the paragons of the curve clusters tend towards an interval of values much smaller in 2000 than twenty years before. CONCLUSION: The functional multivariate pyramidal clustering of time series proved to be efficient and revealed underlying and interpretable clusters among cancer evolutions across countries in the past forty years. doi: 10.1016/j.annepidem.2007.07.064
P61 CONFOUNDING OF INDIRECT EFFECTS IN THE ‘‘REAL WORLD’’: EXPLORING THE RANGE OF BIAS DUE TO A COMMON CAUSE OF THE MEDIATOR AND OUTCOME D Hafeman, Columbia University Several investigators have demonstrated that assessment of indirect effects is biased in the presence of a common cause of the intermediate variable and the outcome. However, little work has been done to determine the degree of bias that will be caused by this type of confounding, and whether this bias will materially affect the identification of indirect effects. To address this crucial question, we have developed simulations based on a sufficient-component cause model for mediation. Confounding of the mediator can be
introduced into such a model by specifying a common component cause of the intermediate variable and the outcome. By testing a range of prevalence proportions for each independent component cause, we vary both mediational effects and the strength of confounding. These simulations are designed to yield both (1) the true indirect effect of interest (pure and/or total indirect effect) and (2) the observed indirect effect. A comparison of these values indicates the range of bias due to uncontrolled confounding of the intermediate variable. Simulation techniques will be applied to a motivating example from the Health Effects of Arsenic Longitudinal Study. In this example, arsenic exposure is associated with mortality, and the investigators hypothesize that this association is at least partially mediated through skin lesions. Based on known prevalences and strengths of association, simulations will be developed to assess the degree to which inference regarding this hypothesis might be biased. doi: 10.1016/j.annepidem.2007.07.065
P62 THE LEGACY OF THE TUSKEGEE SYPHILIS STUDY: ITS IMPACT ON WILLINGNESS TO PARTICIPATE IN BIOMEDICAL STUDIES RV Katz, BL Green, NR Kressin, SS Kegeles, MQ Wang, SA James, SL Russell, C Claudio, JM McCallum, Department of Epidemiology & Health Promotion, NYU College of Dentistry PURPOSE: The origins of the phrase ‘legacy of the Tuskegee Syphilis Study (TSS)’ lie in the widely held belief that Blacks are more reluctant than Whites to participate in biomedical research studies because of that infamous study. This paper is the first to address the validity of the ‘legacy’, a key issue in subject recruitment, in a multi-city, multi-racial, large-scale random survey using a detailed questionnaire. METHODS: The Tuskegee Legacy Project (TLP) Questionnaire, which contains two validated scales, the Likelihood of Participation (LOP) Scale and the Guinea Pig Fear Factor (GPFF) Scale, was administered via random-digit dial telephone interviews to respondents aged 18 years and older in three U.S. cities: Tuskegee, AL; Birmingham, AL; and Hartford, CT. Awareness of the TSS was measured as a yes/no response to two separate questions asking if they had ‘ever heard of the TSS’ while detailed knowledge of the TSS was assessed by a set of seven questions. RESULTS: Response rates, by city, ranged from 49–70% and yielded 327 Black and 499 White respondents. Awareness of the Tuskegee Syphilis Study was significantly higher in Blacks than Whites within each city, and ranged from a high of 93.3% for Blacks in Tuskegee, AL, to a low of 41.9% for Whites in Hartford, CT. While adjusted analyses (age, sex, education and income) revealed no association (p !0.05) between either general awareness or detailed knowledge of the Tuskegee Syphilis Study and willingness to participate (LOP Scale) in biomedical research either for Blacks or Whites, Blacks did show an direct association (pZ0.02) between awareness and increased GPFF scores, indicating increased wariness. CONCLUSION: As these data show no association between awareness of TSS and willingness to participate (albeit in Blacks, awareness was associated with an increased wariness), the longheld belief about the ‘legacy’ of the Tuskegee Syphilis Study that Blacks would be less willing to participate in biomedical studies is not supported by this study. doi: 10.1016/j.annepidem.2007.07.066