1. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 1 Comunicación y Gerencia

2. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 2 Descriptive epidemiology Associate Professor Family & Community Medicine Department King Saud University

3. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 3 Learning Objectives: By the end of this lecture students will be able to: Describe Person, Place and Time characteristics of disease occurrence.Describe Person, Place and Time characteristics of disease occurrence. Identify the uses of descriptive epidemiology Identify the uses of descriptive epidemiology

4. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 4 Descriptive epidemiology describes the distribution of health-related events by time, place, and personal characteristics in order to answer: when (time), where (place), who (person).

5. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 5 I- Time Variation of disease occurrence Annual occurrence, seasonal occurrence, and daily or even hourly occurrence of disease may occur.Annual occurrence, seasonal occurrence, and daily or even hourly occurrence of disease may occur. Knowing time trend of a disease will help health professionals establish control measures.Knowing time trend of a disease will help health professionals establish control measures. Time trend include: Secular trend (long-term) Periodic (cyclic variation) Rapid fluctuation (short time)

6. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 6 Secular (long-term) trends: Graphing the annual cases or rate of a disease over a period of years (Decades or centuries) shows long- term or secular trends in the occurrence of the disease. We commonly use these trends to suggest or predict the future incidence of a disease.

7. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 7 Secular (Long-term trend) is influenced by population features e.g. –Change of degree of susceptibility e.g. by immunization –Socioeconomic –Environmental sanitation and –Nutritional status of a population.

8. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 8 Death rate for Tuberculosis, 1860-1960, United States, Source: US Bureau of the Census, Historical Statistics of the United States; Colonial Times to 1970 (Washington, D.C: Government Printing Office, 1975), Part 1 pp58,63. Note: Data between 1860 and 1900 for Massachusetts only.

9. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 9 Changing TB mortality In the last century, decline in TB mortality was due to: In the last century, decline in TB mortality was due to: –better housing, ventilation –improved nutrition –medical care (streptomycin reduced deaths in UK by 51% 1948-1971).

10. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 10 Recently, TB rates are increasing. why? Environmental: (poor nutrition, housing, hygiene, sociopolitical; wars). Host changes: increased susceptibility (e.g. HIV/AIDS infection), travel, migration,.. Agent changes: Development of drug resistant strains of TB.

11. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 11 Periodic (cyclic variation) cyclic Where disease occurrence for a period then increase again in cyclic pattern e.g. measles in pre vaccination era occur every 2 – 3 years

12. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 12 Seasonality By graphing the occurrence of a disease by week or month over the course of a year or more we can show its seasonal pattern Example: Cases of influenza increases in winter. Food poisoning and diarrhea increase in summer. Seasonality: By graphing the occurrence of a disease by week or month over the course of a year or more we can show its seasonal pattern Example: Cases of influenza increases in winter. Food poisoning and diarrhea increase in summer.

13. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 13 Seasonality: Seasonal patterns may suggest hypotheses about: - how the infection is transmitted - what behavioral factors increase risk - environmental and other possible contributors to disease occurrence.

14. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 14

15. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 15 Rapid fluctuation ( Rapid fluctuation (short time) Usually occur in the form of point source epidemics that appear abruptly and ends abruptly either natural or due to intervention. e.g. food poisoning

16. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 16

17. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 17 Day of week and time of day: Analysis at shorter time periods is especially important for : occupational environmental Conditions that are potentially related to occupational or environmental exposures, which may occur at regularly scheduled intervals.

18. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 18 II- Place characteristics Disease may vary by: place of residence,place of residence, birth place,birth place, place of employment,place of employment, School district,School district, hospital unit, etc.hospital unit, etc.

19. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 19 Place characteristics Analyzing data by place can give an idea of where the agent that causes a disease lives and multiplies, what may carry or transmit it, and how it spreads. Use spot map to locate the possible source or risk factors.

20. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 20 Geography The location of certain place determine its climatic conditions e.g. temperature, humidity, wind,… which favour certain agents and vectors. e.g. malaria, Yellow fever,.. Disease variation by Place may be due to:

21. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 21 Geology The structure of soil affects disease occurrence e.g. Hardness of water ----- CVD Hardness of water ----- CVD Radioactive materials ------ leukemia Radioactive materials ------ leukemia

22. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 22 Chemical and physical environment Iodine deficiency in the soil (oasis) ---goiter Iodine deficiency in the soil (oasis) ---goiter Sulpher dioxide ------- chronic bronchitis Sulpher dioxide ------- chronic bronchitis

23. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 23 Environmental sanitation Filth diseases in poor sanitation Filth diseases in poor sanitation Good sanitation decrease diarrhoeal diseases Good sanitation decrease diarrhoeal diseases

24. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 24 Availability of Health Services Vaccination ---prevent infectious diseases Vaccination ---prevent infectious diseases Health Education ---- healthy behaviour Health Education ---- healthy behaviour Detection and treatment of infectious diseases ------- limit spread. Detection and treatment of infectious diseases ------- limit spread.

25. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 25 III- Person characteristics: In descriptive epidemiology, we also organize or analyze data by “person” characteristics such as: age, race, sex, marital status, socioeconomic status, as well as behaviors and environmental exposures.

26. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 26 Age: Age is probably the single most important “person” attribute, because almost every health-related event or state varies with age. Age affects: Type of disease: e.g.Type of disease: e.g. Neonates ----- congenital anomalies and birth trauma Elderly ------ Degenerative diseases, CVD

27. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 27 Severity of disease: Severity of disease: –Whooping cough is severe under one year –Pneumonia is fatal in early 2 months –Fracture is severe in old age

28. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 28 Clinical form of disease: Thyroxine deficiency ---- cretinism in young ----Myxodema in adults ----Myxodema in adults T.B. ------Miliary in children ----- Pulmonary in adults Explanation of disease variation by age may be explained by exposure to risk factors or exposure to risk factors or degree of immunity or susceptibility degree of immunity or susceptibility. response to a causative agent.

29. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 29 Sex: Some diseases are sex-linked due to: anatomic differences e.g. cancer cervix, cancer prostate or,anatomic differences e.g. cancer cervix, cancer prostate or, genetic differences between the sexes e.g. Haemophilia.genetic differences between the sexes e.g. Haemophilia. Other diseases are related to occupations and environmental exposure which differ in both sexes. e.g. accidents and lung diseasesOther diseases are related to occupations and environmental exposure which differ in both sexes. e.g. accidents and lung diseases

30. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 30 Ethnic and racial groups: Ethnic group: any group of people who have lived together long enough to acquire common characteristics, either biologically or socially. Some races are susceptible to specific diseases e.g. sickle cell anaemia in Negros due to genetic predisposition Some races got immunity due to long exposure

31. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 31 Familial tendency Clustering of some diseases within certain families may be due to: –Genetic factors, or –common exposure to the same dietetic, social, psychological and environmental influences.

32. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 32 Religion Religion usually determine the behaviour of its followers Prohibition of alcohol ----- liver disease Male circumcision------ cancer cervix

33. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 33 Socioeconomic status: Socioeconomic status is measured by: Education ---- health behaviourEducation ---- health behaviour Occupation ----- incomeOccupation ----- income Family income ---- environmental condition, housing conditions, access to health facilitiesFamily income ---- environmental condition, housing conditions, access to health facilities

34. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 34 Occupation Determine the occupational exposure to certain risk factors in work place. Occupation is also one of the determinant of socioeconomic class which affects the disease occurrence (nutritional diseases, filth diseases,…)

35. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 35 Study of disease frequency with marital status indicates that: Study of disease frequency with marital status indicates that: –Mental illnesses are more likely to affect single individuals. –Breast cancer affects more females who remain single or marry late, –Cancer cervix is more common among early married females. Marital Status

36. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 36 Death rates are lower for married than for single. This may be due to: Persons who live dangerously tend to live single. Persons in poor health tend to remain single. There are differences in habits and way of life of single and married people; feeding outdoor,… Marital Status

37. 3/10/2010 Descriptive Epidemiology Dr. Salwa Tayel 37 The End Thank You Website http://faculty.ksu.edu.sa/73234/default.aspx salwatayel@hotmail.com