Unformatted text preview: Chapter 4 Chapter 4 Person, Place and Time Descriptive vs. Analytic Descriptive vs. Analytic Epidemiology Descriptive studiesused to identify a health problem that may exist. Characterize the amount and distribution of disease. Analytic studiesfollow descriptive studies, and are used to identify the cause of the health problem. Objectives of Descriptive Objectives of Descriptive Epidemiology To evaluate and compare trends in health and disease. To provide a basis for planning, provision, and evaluation of health services. To identify problems for analytic studies (creation of hypothesis). Hypothesestheories tested by gathering facts that lead to their acceptance or rejection. Three types:
Positive declaration (research hypothesis) Negative declaration (null hypothesis) Implicit question Descriptive Studies and Descriptive Studies and Epidemiologic Hypotheses Method of Analogy Method of Analogy The mode of transmission and symptoms of a disease of unknown etiology bear a pattern similar to that of a known disease. This information suggests similar etiologies for both diseases. Categories of Descriptive Categories of Descriptive Epidemiology Case reports (counts)simplest category. Case seriessummarize characteristics of patients from major clinical settings. Crosssectional studiessurveys of the population to estimate the prevalence of a disease or exposure. Characteristics of Persons Characteristics of Persons Age Sex Marital Status Race and ethnicity Nativity and migration Religion Socioeconomic status Age Age One of the most important factors to consider when describing the occurrence of any disease or illness. Agespecific distributions can be linear (e.g., cancer), or multimodal (e.g., tuberculosis). Agespecific incidence rates among elderly often inaccurate. Age Effects on Mortality Age Effects on Mortality Biologic clock phenomenonwaning of the immune system may result in increased susceptibility to disease, or aging may trigger appearance of conditions believed to have genetic basis. Example: Alzheimer’s disease. Age Effects (cont’d) Age Effects (cont’d) Latency period—Age effects on mortality may reflect the long latency period between environmental exposures and subsequent development of disease. SexMales SexMales Mortality rate higher for men than for women.
May be due to social factors. May have biological basis. Example: With risk status being equal, men still have higher mortality from CHD. SexFemales SexFemales Females have greater morbidity rates than males for acute and chronic conditions. Generally, death rates for both sexes are declining. Marital Status Marital Status In general, married people have lower rates of morbidity and mortality. Examples: chronic and infectious diseases, suicides, and accidents. Marital Status (cont’d) Marital Status (cont’d) Marriage may operate as a protective or selective factor. Protective: may provide an environment conducive to health. Selective: people who marry may be healthier to begin with. Measurement of Race Measurement of Race Census 2000 changed the race category by allowing respondents to choose one or more race categories. Census 2000 used five categories of race (Exhibit 41). Race/Ethnicity Categories Race/Ethnicity Categories Discussed in Chapter 4 African American American Indian Asian Hispanic/Latino African Americans African Americans In a study of differential mortality in U.S., had the highest rate of mortality of all groups studied. Higher blood pressure levels
Possible influence of stress or diet. Higher rates of hypertensive heart disease. American Indians American Indians For Pima Indians: Age and sexadjusted mortality rate many times that for all races in U.S. for: accidents, cirrhosis, homicide, suicide, and diabetes. Infectious disease is the 10th leading cause of death. For males ages 25 to 34, the death rate is 6.6 times that for all races in U.S. AsiansJapanese AsiansJapanese Comparatively lower mortality rates. Lower rates of CHD and cancer. Low CHD rates attributed to lowfat diet and institutionalized stressreducing strategies. Acculturation Acculturation Defined as modifications that individuals or groups undergo when they come in contact with another country. Provide evidence of the influence of environmental and behavioral factors on chronic disease. Example: Japanese migrants experience a shift in rates of chronic disease toward those of the host country. Hispanics/Latinos Hispanics/Latinos Hispanic Health and Nutrition Examination Survey (HHANES). Examined health and nutrition status of major Hispanic/Latino populations in the U.S. Found high rates of obesity and diabetes among Mexican Americans. San Antonio Heart Study Nativity and Migration Nativity and Migration NativityPlace of origin of the individual. Categories are foreign born and native born. Nativity and migration are related. Impact of Migration Impact of Migration Importation of “Third World” disease by immigrants from developing countries: US also exports drugresistant infectious diseases Programmatic needs resulting from migration: Specialized screening programs (tuberculosis and nutrition). Familiarization with formerly uncommon (in Healthy Migrant Effect Healthy Migrant Effect Observation that healthier, younger persons usually form the majority of migrants. Often difficult to separate environmental influences in the host country from selective factors operative among those who choose to migrate. Religion Religion Certain religions prescribe lifestyles that may influence rates of morbidity and mortality. Example: Seventh Day Adventists Follow vegetarian diet and abstain from alcohol and tobacco use. Have lower rates of CHD, reduced cancer risk, and lower blood pressure. Similar findings for Mormons. Socioeconomic Status Socioeconomic Status Low social class is related to excess mortality, morbidity, and disability rates. Factors include: Poor housing Crowded conditions Racial disadvantage Low income Poor education Unemployment Measurement of Social Class Measurement of Social Class Variables include: Prestige of occupation or social position Educational attainment Income Combined indices of two or more of the above variables Hollingshead and Redlich Hollingshead and Redlich Studied association of socioeconomic status and mental illness. Classified New Haven, Connecticut, into five social classes based on occupational prestige, education, and address. Hollingshead and Redlich Hollingshead and Redlich Findings Strong inverse association between social class and likelihood of being a mental patient under treatment. As social class increased, severity of mental illness decreased. Type of treatment varied by social class. Mental Health and Social Class Mental Health and Social Class In the U.S., the highest incidence of severe mental illness occurs among the lowest social classes. Mental Health and Social Class: Mental Health and Social Class: Two Hypotheses Social causation explanation (breeder hypothesis)conditions associated with lower social class produce mental illness. Downward drift hypothesis—Persons with severe mental disorders move to impoverished areas. Other Correlates of Low Social Other Correlates of Low Social Class Higher rate of infectious disease. Higher infant mortality rate and overall mortality rates. Lower life expectancy. Larger proportion of cancers with poor prognosis. May be due to delay in seeking health care. Characteristics of Place Characteristics of Place Types of place comparisons: International Geographic (withincountry) variations Urban/rural differences Localized occurrence of disease International Comparisons of International Comparisons of Disease Frequency World Health Organization (WHO) tracks international variations in rates of disease. Infectious diseases account for 44% of deaths in less developed nations (4% in developed nations). Variation attributable to climate, cultural factors and dietary habits. WithinCountry Variations in WithinCountry Variations in Rates of Disease Due to variations in climate, geology, latitude, pollution, and ethnic and racial concentrations. In U.S., comparisons can be made by region, state, and/or county. Examples include: higher rates of leukemia in Midwest; state by state variations in intestinal parasites. Urban/Rural Differences in Urban/Rural Differences in Disease Rates Urban diseases and mortality are associated with crowding, pollution, and poverty. Example: lead poisoning in inner cities. Standard Metropolitan Standard Metropolitan Statistical Areas (SMSAs) Established by the U.S. Bureau of the Census to make regional and urban/rural comparisons in disease rates. Localized Place Comparisons Localized Place Comparisons Disease patterns are due to unique environmental or social conditions found in particular areas of interest. Examples include:
Fluorosis: associated with naturally occurring fluoride deposits in water. Goiter: iodine deficiency formerly found in land locked areas of U.S. Geographic Information Systems Geographic Information Systems (GIS) A method to provide a spatial perspective on the geographic distribution of health conditions. A GIS produces a choroplath map that shows variations in disease rates by different degrees of shading. Reasons for Place Variation in Reasons for Place Variation in Disease Gene/environment interaction Examples: sicklecell gene; TaySachs disease. Examples: yaws, Hansen’s disease Example: chemical agents linked to cancer Influence of climate Environmental factors Characteristics of Time Characteristics of Time Cyclic fluctuations Point epidemics Secular time trends Clustering
Temporal Spatial Cyclic Fluctuations Cyclic Fluctuations Periodic changes in the frequency of diseases and health conditions over time. Related to changes in lifestyle of the host, seasonal climatic changes, and virulence of the infectious agent. Examples: higher heart disease mortality in winter; more accidents in summer. Point Epidemics Point Epidemics The response of a group of people circumscribed in place and time to a common source of infection, contamination, or other etiologic factor to which they were exposed almost simultaneously. Examples: foodborne illness; responses to toxic substances; infectious disease. Secular Time Trends Secular Time Trends Refer to gradual changes in the frequency of a disease over long time periods. Example is the decline of heart disease mortality in the U.S. May reflect impact of public health programs, dietary improvements, better treatment, or unknown factors. Clustering Clustering Case clusteringrefers to an unusual aggregation of health events grouped together in space and time.
Temporal clustering: e.g., postvaccination reactions, postpartum depression. Spatial clustering: concentration of disease in a specific geographic area, e.g., Hodgkin’s disease. ...
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- Spring '08