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Descriptive Studies: Person, Place and Time

Dive into the dimensions of person, place, and time in epidemiology to track and analyze disease occurrences. Discover the factors influencing who gets the disease, where it happens, and when it occurs.

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Descriptive Studies: Person, Place and Time

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  1. Descriptive Studies: Person, Place and Time

  2. Descriptive Epidemiology • Includes activities related to characterizing the distribution of diseases within a population Analytical Epidemiology • Concerns activities related to identifying possible causes for the occurrence of diseases

  3. Descriptive Epidemiology • Epidemiological equivalent of the game “20 Questions” • animal, mineral or vegetable? • In Descriptive Epidemiology: • Who? - person • Where? - place • When? - time

  4. PLACE TIME PERSON Think of this as the standard dimensions used to track the occurrence of a disease. Descriptive Epidemiology

  5. Person • WHO is getting the disease? • Many variables are involved and studied, but factors such as sex, age & race often have a major effect.

  6. Characteristics of Person • Age • Sex • Ethnic group • Socioeconomic status • Nativity • Religion • Marital status • Occupation

  7. Age

  8. Age

  9. Sex

  10. Time • WHEN does the disease occur? • “Temporal” • Range from hours to decades • Type of disease dictates “time” element to be used • Graphic format often used • y-axis (vertical) - frequency • x-axis (horizontal) - time

  11. Characteristics Relating to Time • Secular change (long-term) • Point epidemics (short-term) • Cyclic trends • Seasonal variation

  12. Secular Change

  13. Secular Change • Secular changes (“temporal variation”) occur slowly over long periods of time • Longer than one year Incidence Rates of Cancers in Men Incidence Rates of Cancers in Women

  14. Point Epidemics • Short-term changes occur over limited time frames • Hours • Days • Weeks • Months • Used for short-term exposures or diseases with short incubation and/or illness durations

  15. Point Epidemics

  16. Point Epidemics

  17. Cyclic Trends • Cyclic trends may be either long-term or short term events. • Some are “seasonal” while others are cyclic due to other factors: • Immigration • School year • Military deployment

  18. Cyclic Trends

  19. Seasonal Variation • Seasonal variation can be seen for some diseases or conditions falling within a calendar year

  20. Seasonal Variation • Seasonal variation can be used to suggest possible etiology. Migratory Birds?

  21. Time Clustering • Time clustering data can sometimes be used to trace the “beginning” to the introduction of a specific causal agent • Thalidomide & birth defects First marketed in Europe in 1950’s as sleeping pill and to treat morning sickness in pregnant women • Toxic Shock Syndrome • Staphylococcus aureus infectionin women using newly introduced hyperabsorbent tampons

  22. Time Clustering

  23. Place • WHERE are the rates higher? lower? • Geographic location of source • Geographic location of reservoir

  24. John Snow and Cholera

  25. 5 Criteria of Place •  Rate observed in all ethnic groups in the area •  Rate NOT observed in persons of similar groups inhabiting other areas • Healthy persons entering area get ill at same frequency • People who leave do NOT show similar levels • Similar levels of infestation in other species (if zoonotic disease)

  26. Characteristics Relating to Place • International • Variation within countries • Urban-rural • Local • Building Maps

  27. Place Distribution of AIDS in the US 1990

  28. Local

  29. Building Maps

  30. Interactions of Time and Place • Time-place clustering • Migration

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