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Person, place and time.ppt [只读]

Person, place and time
Distribution of disease


? ? ? ? ? ? 1.Searching for patterns 2.Person 3.Place 4.Time 5.Age, period, and birth Cohort 6. Endem

ic, epidemic


1.Searching for patterns
? Diseases do not occur at random. ? Every form of human ill health exhibits a pattern of variation in its frequency within populations, between populations, or over time-in a sense, its epidemiologic fingerprint.


? What’s the meaning of Person, Place, and Time? ? Person: what kinds of people tend to develop the disease, and who tends to be spared? What is unusual about those people? ? Place. Where is the disease especially common or rare, and what is different about those places? ? Time. How does disease frequency change over time, and what other factors are temporally associated with those changes?

? The significance of studying the distribution of person, place and time? ? (1) Generating hypothesis about underlying causes. ? (2)Target efforts at prevention and early detection. ? (3) Assess health disparities. ? (4) Detect emerging threats to public health.

? People can be grouped or distinguished from one to another on a great personal characteristics, like age, gender, race and ethnicity, socioeconomic status, marital status.


? 2.1 Age: ? Nearly every known disease varies in frequency with age, many to a market degree. ? (1)immunity: A few weeks or months after a baby is born, maternally derived antibodies dissipate and leave the infant susceptible to various common infectious diseases.


? (2)Human development: ? Age can also indicate approximately where someone falls in the maturational sequence of physical, mental, and behavioral changes that occur over the human lifespan.



? (3) Slowly progressive disease ? Atherosclerosis can begin in youth, but it generally goes unrecognized until atherosclerotic plaques become large enough to reduce blood flow substantially in major arteries.



? 2.2 Gender ? Differences in disease frequency between the sexes are also the rule, not the exception. Both biological and non-biological mechanisms can be at play. ? Biological: At one extreme, most diseases of the reproductive system occur either only among men (prostate cancer) or only among women (uterine cancer, complications of childbirth). ? For some diseases of organs related to reproduction, the association with gender is not absolute. Like breast cancer among males.

? Besides diseases of the reproductive system, many other diseases predominate in one gender or the other for reasons that are believed to be biological. ? Red-green color blindness is inherited as a recessive trait on the X-chromosome and for this reason appears almost entirely in males.



? Non-biological: ? The major differences in social roles and health-related behavior between men and women almost certainly underlie many gender differences in disease frequency. Gender serves as a marker for exposure to more proximate disease causes.




? 2.3 Race and Ethnicity ? Race and ethnicity concern self-perceived membership in groups defined by skin color, ancestral place of residence, language, and cultural heritage. ? It often serves as a marker for a complex mix of social conditions, cultural traditions, health behaviors, and other non-biological factors.



? 2.4 Socioeconomic Status ? Dr. Joseph Goldberger and pellagra ? Which is characterized by symmetrical skin eruptions; in advanced cases, gastrointestinal and nervous-system symptoms also appear.



? 2.5 Marital status ? Marital status can be associated with disease frequency for many reasons. ? The incidence of cervical cancer was found to be lower in unmarried women than in married women.


3. Place




? 4.1 Secular Trends ? Patterns of change in disease frequency over periods of calendar time termed secular trends. ?



? ? ? ? ?

4.2 Cyclical Variation Annual cycles. Monthly cycles Weekly cycles Diurnal cycles: Sudden infant death syndrome (SIDS) cases have been found to be most likely to occur-or at least to be discovered. (6:00am –noon)


? 4.3 Time relative to a salient Event ? Another way to consider time-related variation in disease occurrence is to examine when cases occur relative to some event that might have special importance for the disease in questions.



? 4.4 Age, period, and birth cohort




5. Endemic and epidemic
? Endemic is defined as the habitual presence of a disease within a given geographic area. ? Epidemic is defined as the occurrence in a community or region of a group of illness of similar nature, clearly in excess of normal expectancy, and derived from a common or from a propagated source.

? In Japan, a National Nutritional Survey has been done annually for over 50 years. Each year the survey obtains anthropometric data on a random sample of Japanese adults. Figure 7.21 shows mean body weight among Japanese men in relation to age and survey decade. Data from ten consecutive annual surveys were combined into each of the five survey decades identified on the right side of the figure. On the basis of these results, would you expect that a typical 35-yearold Japanese man will weigh more or less ten years from now than he weighs today?




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