1. Injury Epidemiology Moving from Descriptive to Analytic Research Approaches readings Thomas Songer, PhD University of Pittsburgh tjs@pitt.edu

2. Learning objective n To differentiate between various study designs used in injury epidemiology

3. Background n Epidemiology looks to control or prevent disease n In this endeavor, epidemiology seeks to –describe the frequency of disease and it’s distribution consider person, place, time factors –assess determinants of disease consider host, agent, environment

4. Types of primary studies n Descriptive studies –describe occurrence of outcome n Analytic studies association –describe association between exposure and outcome

5. Basic Question in Analytic Epidemiology Are exposure and disease linked? ExposureDisease

6. Big Picture n To prevent and control disease n In a coordinated plan, look to –identify hypotheses on what is related to disease and may be causing it –formally test these hypotheses Study designs direct how the investigation is conducted

7. A Model of Injury Control Monitor incidence Identify risk factors InterveneEvaluate DescriptiveAnalytic

8. What designs exist to identify and investigate factors in injuries?

9. Study Designs Case report Case series Descriptive Epidemiology Descriptive RCT Before-After study Cross-sectional study Case-Crossover study Case-Control study Cohort study Analytic Ecologic study

10. Framework for Understanding Injuries Increasing Knowledge of Disease/Exposure 19828486889092941996 Case- Control Studies Cross- Sectional Studies Cohort Studies Case Series

11. Descriptive Studies Case-control Studies Cohort Studies Develop hypothesis Investigate it’s relationship to outcomes Define it’s meaning with exposures Clinical trials Test link experimentally Increasing Knowledge of Disease/Exposure

12. Descriptive Studies

13. Injury Surveillance

14. Descriptive Studies - An Example The Rockets' Red Glare, the Bombs Bursting in Air: Fireworks-related Injuries to Children. Pediatrics 98(1):1-9, 1996

15. Injury Police Hospital Self-Treat Robertson, 1992 doctor EMS Rehab Center Trauma Center Morgue Emergency Dept.

16. Data Sources and Injury Severity Survey Doctor visit Hospital admiss. Trauma center Death certificate No injury Mild Moderate Severe Fatal Rogams, 1995

17. Case Report Case Series Descriptive Epidemiology Study One case of unusual injury finding Multiple cases of injury finding Population-based cases with denominator

18. Causes of Death in Travelers CardiovascularInjury Medical CancerSuicide/Homicide Other Hargarten, 1991

19. Scooter Injuries n Study design n Definition of injury n Data Sources n Population n Bias n Findings n Descriptive study n ED visits n CPSC-NEISS, IPII (fatal) n United States n reporting of scooters n scooter related injuries have increased over the last 2 yrs http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4949a2.htm

20. Descriptive Studies Analytic Studies

22. Case-Control Studies Cases: injured Controls: not injured

23. Case-Control Studies - An Example Characteristics of Fatally Injured Pedestrians No. % None3 17.6 13 76.5 10-405 29.4 1 5.9 50-901 5.9 1 5.9 100-1402 11.8 1 5.9 150-1905 29.4 - 0.0 200-2401 5.9 - 0.0 Lab loss- 0.0 1 5.9 Cases Controls Blood Alcohol Concentration

24. Cohort Studies Cases: have exposure Controls: no exposure

25. Rates & Risks of Youth Sports Injury in Allegheny County Cohort Studies - An Example

26. Limitations of Existing Studies n Do not take into account the injury risk among non-participants, cannot determine the relative risk of sports participation n Do not quantify the “exposure” or the “dose” of activity, do not know the risk of injury per “activity hour”

27. Allegheny County Adolescent Injury Surveillance Baseline 3 years Cases: high physical activity Controls: low physical activity

28. Injury Surveillance n Continuous surveillance - 3 years n Quarterly screening of students during physical education class. n Collected detailed injury information. –Type, diagnosis, treatment, location. n Validated by parent - 92% n Random sample of medical records

29. Definitions n Injury –Any event that produced bodily damage and required treatment by medical personnel (MD, ED, Specialist, Hospitalization) n Severe Injury –any injury treated within 24 hours of onset of symptoms, seen at an ED, by a specialist, or hospitalized, and results in > 7 day activity restriction.

30. Injury Incidence Percent Injured

31. Relation of Team Sport Participation to Injury Risk - Males

32. Relation of Team Sport Participation to Injury Risk - Females

33. Sample Size Incidence of LBP (%) Sample Size & Low Back Pain Incidence

34. Case-Crossover Studies

35. Conclusions n Descriptive studies are the most common approaches used today in injury research n Analytic designs are often difficult to conduct, but the yield in terms of new information can be great.