DESCRIPTIVE
EPIDEMIOLOGY
PRESENTED BY:
BUSHRA FARHAN
BDS 2010 BATCH
UNDER THE GUIDANCE OF:
DR.NEHA AGARWAL
DR.AMITABH VARS...
EPI DEMOS LOGOS
Upon,on,befall People,population,man the Study of
EPIDEMIOLOGY
WHAT IS EPIDEMIOLOGY?
THE STUDY OF THE
DISTRIBUTION DETERMINANTS
OF HEALTH RELATED STATES OR EVENTS IN
SPECIFIED POPULATIO...
EPIDEMIOLOGICAL
METHODS
DESCRIPTIVE
EPIDEMIOLOGY
ANALYTICAL
EPIDEMIOLOGY
EXPERIMENTAL
EPIDEMIOLOGY
DESCRIPTIVE
EPIDEMIOLOGY
 CONCERNED WITH OBSERVATION OF THE DISTRIBUTION
OF THE DISEASE OR ANY HEALTH RELATED EVENTS IN
H...
o DESCRIBES THE PATTERN OF OCCURRENCE OF DISEASE
OR A CONDITION RELATIVE TO OTHER CHARACTERISTICS
OF THE POPULATION.
o FIR...
STEPS :
DEFINING THE POPULATION TO BE STUDIED.
DEFINING THE DISEASE UNDER STUDY.
DESCRIBING THE DISEASE IN TERMS OF PERSON...
1.DEFINING THE POPULATION
TO BE STUDIED:
DEFINED
POPULATION
POPULATION TO
BE STUDIED IS
DEFINED IN
TERMS OF:
TOTAL NUMBER COMPOSITION OF
THE INDIVIDUALS
 THE POPULATION SELECTED FOR THE STUDY SHOULD ALWAYS REMAIN
STABLE,WITHOUT ANY MIGRATION INTO OR OUT OF THE AREA.
 PARTI...
2.DEFINING THE DISEASE UNDER STUDY
 THE DISEASE NEEDS TO BE DEFINED WITH AN
 IT CLEARLY INDICATES THE CRITERIA BY WHICH ...
3.DESCRIBING THE DISEASE UNDER
STUDY:
 WHO?
 WHERE?
 WHEN?
PERSON
PLACE
TIME
 TIME DISTRIBUTION
 SHORT TERM FLUCTUATIONS:
EPIDEMIC
THE OCCURENCE OF CASES OF AN ILLNESS OR OTHER HEALTH RELATED
EVENTS IN A REGION OR A C...
TYPES OF EPIDEMICS:
1.COMMON
SOURCE
•SINGLE EXPOSURE OR POINT SOURCE
•CONTINUOUS OR MULTIPLE EXOSURE
2.PROPAGATED
•PERSON ...
COMMON SOURCE EPIDEMICS:
SINGLE EXPOSURE
•RESPONSE OF A GROUP OF
PEOPLE TO A SOURCE OF
INFECTION OR
CONTAMINATION TO WHICH...
PROPAGATED EPIDEMIC:
a.
PERSON TO
PERSON
b.
ARTHROPOD
VECTOR
c.
ANIMAL
RESERVOIR
 MOST OFTEN OF INFECTIOUS ORIGIN.
 USUALLY OCCURS IN PLACES WHERE LARGE NUMBER OF SUSCEPTIBLE
INDIVIDUALS ARE AGGREGATED...
2.PERIODIC FLUCTUATIONS
SEASONAL TRENDS CYCLIC TRENDS
3.LONG TERM OR SECULAR TRENDS
o CHANGES IN DISEASE FREQUENCY THAT OCCUR GRADUALLY OVER
A LONG PERIOD OF TIME.
o ORAL CANCE...
PLACE DISTRIBUTIONS:
THE GEOGRAPHIC PATTERN OF DISEASE PROVIDE CLUES ABOUT THE
ETIOLOGY OF DISEASE.
INTERNATIONAL
VARIATI...
MIGRANT STUDIES:
 EVALUATE THE ROLE OF POSSIBLE GENETIC AND ENVIRONMENTAL
FACTORS IN THE OCCURRENCE OF DISEASE IN A POPUL...
COMPARING THE RATE OF OCCURRENCE OF DISEASE FOR MIGRANTS WITH
THOSE OF THEIR KIN WHO HAVE STAYED AT HOME.
COMPARISON OF GE...
COMPARING THE RATE OF OCCURRENCE OF DISEASE IN MIGRANTS WITH
THE LOCAL POPULATION OF THE HOST COUNTRY.
COMPARISON OF GENET...
PERSON DISTRIBUTION:
 AGE
 BIMODALITY
 GENDER
 ETHNIC GROUP
 OCCUPATION
 SOCIOECONOMIC STATUS
 MARITAL STATUS
 BE...
•AGE:
IT MAY ASSIST IN UNDERSTANDING THE
FACTORS RESPONSIBLE FOR THE
DEVELOPMENT OF DISEASE.
AGE MAY PRODUCE INDIRECT EFFE...
•BIMODALITY:
 OCCURRENCE OF TWO SEPARATE PEAKS IN THE AGE INCIDENCE OF
A DISEASE.
 INDICATES THAT MATERIAL IS NOT HOMOGE...
GENDER:VARIATION IN DISEASE FREQUENCY IN MALES & FEMALES.
SOCIOECONOMIC STATUS:UPPER SOCIAL CLASS
INDIVIDUAL EXHIBIT BETTE...
• OCCUPATION:
 AS A MEASURE OF SOCIOECONOMIC STATUS.
 FOR IDENTIFICATION OF RISKS ASSOCIATED WITH EXPOSURE TO AGENTS
PEC...
• BEHAVIOUR:
 HABITS LIKE SMOKING,ALCOHOLISM,DRUG ABUSE,SEDENTARY LIFESTYLE OR
OVEREATING CAN LEAD TO
 CERTAIN INFECTIOU...
4.MEASUREMENT OF DISEASE:
DONE IN TWO TERMS:
MORBIDITY
MORTALITY
INCIDENCE PREVALENCE
EXPRESSED IN TERMS OF
LONGITUDINAL
S...
CROSS SECTIONAL STUDIES
 A SET OF INDIVIDUALS ARE CHOSEN WHO MAY BE A REPRESENTATIVE SAMPLE
OF THE CHOSEN POPULATION.
 T...
 “CROSS SECTIONAL STUDIES DONE FOR LONGER DURATION BY REPEATING
PERIODICALLY.”
 SAME INDIVIDUALS ARE EXAMINED UPON REPEA...
USEFUL
FOR:
STUDYING THE
NATURAL HISTORY
OF THE DISEASE & ITS
OUTCOME.
IDENTIFYING THE
RISK FACTORS
ASSOCIATED
WITH THE
DI...
5.COMPARING WITH KNOWN INDICES
BY MAKING COMPARISON BETWEEN DIFFERENT POPULATIONS & SUBGROUPS OF
THE SAME POPULATION
POSSI...
6.FORMULATION OF AN ETIOLOGICAL
HYPOTHESIS
HYPOTHESIS:
“A SUPPOSITION ARRIVED AT FROM BY OBSERVATION OR BY
REFLECTION”.
SPECIFICATIONS OF HYPOTHESIS:
POPULATION
THE CAUSE BEING
CONSIDERED
THE EXPECTED
EFFECT
DOSE-RESPONSE
RELATIONSHIP
TIME-RE...
USES:
PROVIDES DATA WITH REGARD TO THE TYPES OF DISEASE
PROBLEMS & THEIR MAGNITUDE IN THE COMMUNITY.
PROVIDES INFORMATION ...
THANK YOU!!
De sepidemiology
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De sepidemiology

  1. 1. DESCRIPTIVE EPIDEMIOLOGY PRESENTED BY: BUSHRA FARHAN BDS 2010 BATCH UNDER THE GUIDANCE OF: DR.NEHA AGARWAL DR.AMITABH VARSHNEY DR. N.D.GUPTA
  2. 2. EPI DEMOS LOGOS Upon,on,befall People,population,man the Study of EPIDEMIOLOGY
  3. 3. WHAT IS EPIDEMIOLOGY? THE STUDY OF THE DISTRIBUTION DETERMINANTS OF HEALTH RELATED STATES OR EVENTS IN SPECIFIED POPULATIONS,& THE APPLICATION OF THIS STUDY TO THE CONTROL OF HEALTH PROBLEMS. -JOHN M.LAST(1988)
  4. 4. EPIDEMIOLOGICAL METHODS DESCRIPTIVE EPIDEMIOLOGY ANALYTICAL EPIDEMIOLOGY EXPERIMENTAL EPIDEMIOLOGY
  5. 5. DESCRIPTIVE EPIDEMIOLOGY  CONCERNED WITH OBSERVATION OF THE DISTRIBUTION OF THE DISEASE OR ANY HEALTH RELATED EVENTS IN HUMAN POPULATIONS & THE IDENTIFICATION OF THE CHARACTERISTICS WITH WHICH THE DISEASE OR CONDITION UNDER STUDY SEEMS TO BE ASSOCIATED.
  6. 6. o DESCRIBES THE PATTERN OF OCCURRENCE OF DISEASE OR A CONDITION RELATIVE TO OTHER CHARACTERISTICS OF THE POPULATION. o FIRST PHASE OF ANY EPIDEMIOLOGICAL INVESTIGATION.
  7. 7. STEPS : DEFINING THE POPULATION TO BE STUDIED. DEFINING THE DISEASE UNDER STUDY. DESCRIBING THE DISEASE IN TERMS OF PERSON,PLACE & TIME. MEASUREMENT OF THE DISEASE. COMPARING WITH KNOWN INDICES. FORMULATING AN ETIOLOGICAL HYPOTHESIS
  8. 8. 1.DEFINING THE POPULATION TO BE STUDIED: DEFINED POPULATION
  9. 9. POPULATION TO BE STUDIED IS DEFINED IN TERMS OF: TOTAL NUMBER COMPOSITION OF THE INDIVIDUALS
  10. 10.  THE POPULATION SELECTED FOR THE STUDY SHOULD ALWAYS REMAIN STABLE,WITHOUT ANY MIGRATION INTO OR OUT OF THE AREA.  PARTICIPATION OF THE PEOPLE OF THE COMMUNITY CHOSEN.  PRESENCE OF HEALTH FACILITY IN CLOSE PROXIMITY TO THE COMMUNITY.  IMPORTANCE: IT FORMS THE POPULATION AT RISK,WHICH PROVIDES THE DENOMINATOR FOR CALCULATING THE RATES OF FREQUENCY AND DISTRIBUTION OF THE DISEASE.
  11. 11. 2.DEFINING THE DISEASE UNDER STUDY  THE DISEASE NEEDS TO BE DEFINED WITH AN  IT CLEARLY INDICATES THE CRITERIA BY WHICH THE DISEASE CAN BE MEASURED. OPERATIONAL DEFINITION WITH WHICH THE DISEASE OR CONDITION CAN BE IDENTIFIED & MEASURED IN THE DEFINED POPULATION WITH A DEGREE OF ACCURACY.
  12. 12. 3.DESCRIBING THE DISEASE UNDER STUDY:  WHO?  WHERE?  WHEN? PERSON PLACE TIME
  13. 13.  TIME DISTRIBUTION
  14. 14.  SHORT TERM FLUCTUATIONS: EPIDEMIC THE OCCURENCE OF CASES OF AN ILLNESS OR OTHER HEALTH RELATED EVENTS IN A REGION OR A COMMUNITY CLEARLY IN EXCESS OF NORMAL EXPECTANCY.
  15. 15. TYPES OF EPIDEMICS: 1.COMMON SOURCE •SINGLE EXPOSURE OR POINT SOURCE •CONTINUOUS OR MULTIPLE EXOSURE 2.PROPAGATED •PERSON TO PERSON •ARTHROPOD VECTOR •ANIMAL RESERVOIR 3.SLOW OR MODERN
  16. 16. COMMON SOURCE EPIDEMICS: SINGLE EXPOSURE •RESPONSE OF A GROUP OF PEOPLE TO A SOURCE OF INFECTION OR CONTAMINATION TO WHICH THEY WERE EXPOSED ALMOST SIMULTANEOUSLY. •CASES DEVELOP WITHIN 1 INCUBATION PERIOD. •Eg:FOOD POISONING CONTINUOUS EXPOSURE •EXPOSURE FROM THE SAME SOURCE MIGHT BE PROLONGED. •NEED NOT BE AT THE SAME PLACE OR AT THE SAME TIME. •Eg:CONTAMINATED WATER
  17. 17. PROPAGATED EPIDEMIC: a. PERSON TO PERSON b. ARTHROPOD VECTOR c. ANIMAL RESERVOIR
  18. 18.  MOST OFTEN OF INFECTIOUS ORIGIN.  USUALLY OCCURS IN PLACES WHERE LARGE NUMBER OF SUSCEPTIBLE INDIVIDUALS ARE AGGREGATED OR WHERE THERE IS A REGULAR SUPPLY OF NEW SUSCEPTIBLE PERSONS,WHICH TENDS TO LOWERTHE HERD IMMUNITY.
  19. 19. 2.PERIODIC FLUCTUATIONS SEASONAL TRENDS CYCLIC TRENDS
  20. 20. 3.LONG TERM OR SECULAR TRENDS o CHANGES IN DISEASE FREQUENCY THAT OCCUR GRADUALLY OVER A LONG PERIOD OF TIME. o ORAL CANCER HAS SHOWN AN UPWARD TREND IN PAST 50 yrs WHILE TB,TYPHOID & POLIO HAVE SHOWN A DOWNWARD TREND.
  21. 21. PLACE DISTRIBUTIONS: THE GEOGRAPHIC PATTERN OF DISEASE PROVIDE CLUES ABOUT THE ETIOLOGY OF DISEASE. INTERNATIONAL VARIATIONS NATIONAL VARIATIONS RURAL-URBAN VARIATIONS LOCAL DISTRIBUTIONS
  22. 22. MIGRANT STUDIES:  EVALUATE THE ROLE OF POSSIBLE GENETIC AND ENVIRONMENTAL FACTORS IN THE OCCURRENCE OF DISEASE IN A POPULATION.  USUALLY OF TWO TYPES:
  23. 23. COMPARING THE RATE OF OCCURRENCE OF DISEASE FOR MIGRANTS WITH THOSE OF THEIR KIN WHO HAVE STAYED AT HOME. COMPARISON OF GENETICALLY SIMILAR GROUPS LIVING UNDER DIFFERENT ENVIRONMENTAL CONDITIONS. IF RATE OF DISEASE OCCURRENCE IN MIGRANTS SIMILAR TO THAT OF COUNTRYOF ADOPTION OVER A PERIOD OF TIME: ENVIRONMENTAL FACTOR
  24. 24. COMPARING THE RATE OF OCCURRENCE OF DISEASE IN MIGRANTS WITH THE LOCAL POPULATION OF THE HOST COUNTRY. COMPARISON OF GENETICALLY DIFFERENT GROUPS LIVING IN A SIMILAR ENVIRONMENT. IF RATE OF DISEASE OCCURRENCE AMONG THE MIGRANTS ARE SIMILAR TO THEIR COUNTRY OF ORIGIN: GENETIC FACTORS
  25. 25. PERSON DISTRIBUTION:  AGE  BIMODALITY  GENDER  ETHNIC GROUP  OCCUPATION  SOCIOECONOMIC STATUS  MARITAL STATUS  BEHAVIOUR
  26. 26. •AGE: IT MAY ASSIST IN UNDERSTANDING THE FACTORS RESPONSIBLE FOR THE DEVELOPMENT OF DISEASE. AGE MAY PRODUCE INDIRECT EFFECT THAT MUST BE TAKEN ACCOUNT OF. ALSO USEFUL FOR ADMINISTRATIVE PURPOSES.
  27. 27. •BIMODALITY:  OCCURRENCE OF TWO SEPARATE PEAKS IN THE AGE INCIDENCE OF A DISEASE.  INDICATES THAT MATERIAL IS NOT HOMOGENOUS,THAT ENTITY UNDER EXAMINATION MAY BE DIVIDED INTO TWO.
  28. 28. GENDER:VARIATION IN DISEASE FREQUENCY IN MALES & FEMALES. SOCIOECONOMIC STATUS:UPPER SOCIAL CLASS INDIVIDUAL EXHIBIT BETTER HEALTH STATE. MARITAL STATUS:HELPS IN INVESTIGATING POSSIBLE INFLUENCE OF A COMMON ENVIRONMENT ON THE HEALTH OF MARITAL PARTNERS.
  29. 29. • OCCUPATION:  AS A MEASURE OF SOCIOECONOMIC STATUS.  FOR IDENTIFICATION OF RISKS ASSOCIATED WITH EXPOSURE TO AGENTS PECULIAR TO CERTAIN OCCUPATIONS.  TO IDENTIFY GROUPS WHOSE GENERAL PATTERNS OF LIFE VARY BECAUSE OF DIFFERENT DEMANDS MADE BY THEIR OCCUPATION.
  30. 30. • BEHAVIOUR:  HABITS LIKE SMOKING,ALCOHOLISM,DRUG ABUSE,SEDENTARY LIFESTYLE OR OVEREATING CAN LEAD TO  CERTAIN INFECTIOUS DISEASES LIKE TYPHOID,CHOLERA SPREAD THROUGH MOVEMENT OF PEOPLE IN MASSES SUCH AS IN PILGRIMAGE. CORONARY ARTERY DISEASE, HYPERTENSION,CANCERS,OBESITY ETC
  31. 31. 4.MEASUREMENT OF DISEASE: DONE IN TWO TERMS: MORBIDITY MORTALITY INCIDENCE PREVALENCE EXPRESSED IN TERMS OF LONGITUDINAL STUDY CROSS SECTIONAL STUDY
  32. 32. CROSS SECTIONAL STUDIES  A SET OF INDIVIDUALS ARE CHOSEN WHO MAY BE A REPRESENTATIVE SAMPLE OF THE CHOSEN POPULATION.  THE MEASUREMENTS OF EXPOSURE AND EFFECT ARE MADE AT THE SAME TIME.  THIS PROVIDES INFORMATION ON THE RELATIONSHIP BETWEEN A DISEASE AND OTHER VARIABLES OF INTEREST.  EASY & ECONOMICAL TO CARRY OUT.
  33. 33.  “CROSS SECTIONAL STUDIES DONE FOR LONGER DURATION BY REPEATING PERIODICALLY.”  SAME INDIVIDUALS ARE EXAMINED UPON REPEATED OCCASIONS & THE CHANGES WITHIN GROUP ARE RECORDED IN TERMS OF ELAPSED TIME BETWEEN OBSERVATIONS.  BUT MORE TIME CONSUMING. LONGITUDINAL STUDIES
  34. 34. USEFUL FOR: STUDYING THE NATURAL HISTORY OF THE DISEASE & ITS OUTCOME. IDENTIFYING THE RISK FACTORS ASSOCIATED WITH THE DISEASE. CALCULATING THE INCIDENCE RATE OF THE DISEASE.
  35. 35. 5.COMPARING WITH KNOWN INDICES BY MAKING COMPARISON BETWEEN DIFFERENT POPULATIONS & SUBGROUPS OF THE SAME POPULATION POSSIBLE TO REACH A CONCLUSION WITH REGARD TO THE DISEASE ETIOLOGY & TO IDENTIFY SUBGROUPS AT RISK.
  36. 36. 6.FORMULATION OF AN ETIOLOGICAL HYPOTHESIS HYPOTHESIS: “A SUPPOSITION ARRIVED AT FROM BY OBSERVATION OR BY REFLECTION”.
  37. 37. SPECIFICATIONS OF HYPOTHESIS: POPULATION THE CAUSE BEING CONSIDERED THE EXPECTED EFFECT DOSE-RESPONSE RELATIONSHIP TIME-RESPONSE RELATIONSHIP
  38. 38. USES: PROVIDES DATA WITH REGARD TO THE TYPES OF DISEASE PROBLEMS & THEIR MAGNITUDE IN THE COMMUNITY. PROVIDES INFORMATION ON THE ETIOLOGY OF A DISEASE & HELPS IN THE FORMULATION OF AN ETIOLOGICAL HYPOTHESIS. PROVIDES DATA REQUIRED FOR THE PLANNING,ORGANIZING & EVALUATING PREVENTIVE & CURATIVE SERVICES. LEADS THE PATH FOR FURTHER RESEARCH WITH REGARD TO A PARTICULAR DISEASE PROBLEM.
  39. 39. THANK YOU!!
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