1. Epidemiology Applications Fran C. Wheeler, Ph.D School of Public Health University of South Carolina Columbia, SC 29208 (803) 777-5054 Fran.wheeler@sc.edu

2. Developed as part of an Enhanced AHEC Community Partnership for Health Professions Workforce and Educational Reform project funded by the Health Resource and Service Administration (HRSA)

3. OBJECTIVES l applications of epidemiologic method

4. Assessing Risk and Burden of Disease l Relative Risk l Odds Ratio l Attributable Risk

5. Relative Risk l Calculated to identify differences in disease rates between exposed and unexposed groups. l Risk of disease among exposed  risk of disease among unexposed s RR = 1, no difference s RR > 1, association between exposure and disease

6. Odds Ratio l Calculated to identify likelihood of exposure to a risk when comparing two groups, one with and one without disease. l Exposure odds in disease group  exposure odds in non-disease group s Ratio = 1, no association s Ratio > 1, association between exposure and disease

7. Attributable Risk l Calculated to identify the proportion of disease among exposed people that actually results from the exposure l Individual attributable risk = RR - 1 / RR l Population attributable risk = Pe (RR - 1) / 1 + Pe (RR - 1), where Pe = proportion of population exposed

8. Epidemiology in Action l Outbreak and Cluster Investigations l Public Health Surveillance l Community Screening Programs

9. Outbreaks and Clusters l Outbreak: an epidemic limited to a localized increase in the incidence of a disease l Cluster: an aggregation of relatively uncommon events or diseases in space and/or time in amounts believed or perceived to be greater than expected by chance

10. Characteristics of Outbreak Investigations l Infectious disease or condition l Etiologic agent is transmissible organism l Short time frame for investigation (hours, days) l Moderate to large effect estimates l Moderate to high exposure levels

11. Characteristics of Outbreak Investigations, cont. l Acute exposure period (hours, days) l Laboratory confirmation common l Moderate to high possibility of establishing cause and effect l Most common study design: retrospective cohort

12. Characteristics of Cluster Investigations l Non-infectious disease or condition l Often unknown or combined etiologic agents l Longer time frame for investigation (weeks or months) l Weak to moderate effect estimates l Low exposure levels

13. Characteristics of Cluster Investigations, cont. l Chronic exposure period (years or decades) l Laboratory confirmation uncommon l Low possibility of establishing cause and effect l Most common study design: case- control

14. Challenges of Cluster Investigations l Active or passive approach l Epidemiology or public health education l Data sources and denominators l Costs and yields

15. Public Health Surveillance l Ongoing systematic collection, analysis and interpretation of outcome-specific health data l Closely integrated with the timely dissemination of those data to those responsible for preventing and controlling disease or injury

16. Sources of Surveillance Data l Reports of health events l Reporting from laboratories l Registries l Vital statistics l Periodic surveys l Information on environmental exposures l Information from other organizations

17. Uses of Surveillance Information l Immediate detection l Annual dissemination l Archival information

18. Community Screening Programs l Defining the target population l Setting priorities among diseases and conditions l Choosing effective screening tests l Assessing the effectiveness of screening programs

19. Screening Tests

20. Hypothetical Example

21. Sample Data l AIDS l Syphilis l Diabetes

22. *Adjusted for reporting delays Quarter-Year of Diagnosis/Death N u m b e r o f C a s e s / D e a t h s Estimated Incidence of AIDS and Deaths of Adults with AIDS*, 1985 - June 1998, United States 1993 definition implementation 25,000 20,000 15,000 10,000 5,000 0 1985 1986 1987 19881989 199019911992 1993 1995 1996 1994 1997 1998 AIDS Deaths

23. Female N=113,414 3 Age at Diagnosis AIDS Cases by Age and Sex Reported 1981-1998, United States 0 0 1020 304050 6070 80 90 5,000 10,000 15,000 20,000 25,000 30,000 35,000 Male N=574,783 Number of Cases

24. Estimated Number of Persons Living with AIDS 1993 -1998, by Sex, United States Year Thousands 199319941995 1996 19971998 250 200 150 100 50 0 Men Women

25. American Indian/ Alaska Native Black, not Hispanic Hispanic Asian/Pacific Islander White, not Hispanic 199319941995199619971998 Year 0 20 40 60 80 100 120 140 Estimated Number of Persons Living with AIDS 1993 - 1998, by Race/Ethnicity, United States Thousands

26. Year 19931994199519961997 0 1998 2,500 2,000 1,500 1,000 500 American Indian/ Alaska Native Asian/Pacific Islander Estimated Number of Persons Living with AIDS 1993 - 1998, by Race/Ethnicity, United States Persons

27. 2020 4040 6060 12 0 10 0 8080 0 U.S. dependencies and possessions Midwest Northeast South 199519961997199819941993 Year Estimated Number of Persons Living with AIDS 1993 -1998, by Region, United States West Thousands

28. 0 10 20 30 40 50 60 70 Year of Report American Indian/ Alaska Native Black, not Hispanic Hispanic Asian/Pacific Islander White, not Hispanic 1985198719891991199319951997 Proportion of AIDS Cases, by Race/Ethnicity Year of Report,1985-1998, United States Percent of Cases

29. Excludes cases with other or unreported risk pending medical record review and reclassification. 1985198719891991199319951997 Year of Report AIDS Cases by Exposure Category and Year of Report, 1985-1998, United States 0 10 20 30 40 50 60 70 80 MSM & IDU Men who have sex with men (MSM) Injection drug use (IDU) Heterosexual contact Percent of Cases

30. 4.7 13.5 VI 29.6 PR 44.3 <5 5 - 14.9 15+ AIDS Rates per 100,000 Population Reported in1998 Rate per 100,000 DE MA RI CT NJ MD DC NH 26.3 20.3 23.4 189.1 31.9 15.0 12.9 3.5 11.1 13.8 8.0 7.9 36.5 16.9 2.6 10.8 2.6 4.8 7.1 21.8 2.5 7.3 4.0 15.1 8.1 3.3 4.3 14.8 12.0 47.9 10.4 0.9 6.1 8.2 8.5 6.2 14.5 20.3 2.0 12.8 20.1 6.6 14.7 7.8 4.7 3.9 17.3 1.2 VT 3.4

31. 71% 12% 13% AIDS Cases N=48,269* Population N=274,766,000 AIDS Cases Reported in 1998 and Estimated 1998 Population, by Race/Ethnicity, United States White, not Hispanic Black, not Hispanic Hispanic Asian/Pacific Islander American Indian/ Alaska Native 33% 45% 20% *Includes 211 persons with unknown race/ethnicity <1% 1%1% 1%1% 4%4%

32. AIDS in Adult/Adolescent Men by Race/Ethnicity per 100,000 Population, Reported in 1998 United States Race/Ethnicity White, not Hispanic Black, not Hispanic Hispanic Asian/Pacific Islander American Indian/ Alaska Native Total* * Includes 162 men whose race/ethnicity is unknown. Cases 14,027 14,740 7,511 329 117 36,886 Rate 18 125 58 9 16 34

33. Northeast N=14,399 North Central N=4,317 South N=19,474 West N=8,121 Metropolitan area 50,000- 499,999 population Non- metropolitan area AIDS by Region & Size of Place of Residence Reported in 1998, United States % 93.14.52.4 76.314.49.3 75.613.510.9 86.78.25.0 % Metropolitan area 500,000 population