Epidemiology Applications

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 SOUTH CAROLINA AHEC 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) SOUTH CAROLINA AHEC OBJECTIVES  applications of epidemiologic method SOUTH CAROLINA AHEC Assessing Risk and Burden of Disease    Relative Risk Odds Ratio Attributable Risk SOUTH CAROLINA AHEC Relative Risk   Calculated to identify differences in disease rates between exposed and unexposed groups. Risk of disease among exposed  risk of disease among unexposed   RR = 1, no difference RR > 1, association between exposure and disease SOUTH CAROLINA AHEC Odds Ratio   Calculated to identify likelihood of exposure to a risk when comparing two groups, one with and one without disease. Exposure odds in disease group  exposure odds in non-disease group   Ratio = 1, no association Ratio > 1, association between exposure and disease SOUTH CAROLINA AHEC Attributable Risk    Calculated to identify the proportion of disease among exposed people that actually results from the exposure Individual attributable risk = RR - 1 / RR Population attributable risk = Pe (RR 1) / 1 + Pe (RR - 1), where Pe = proportion of population exposed SOUTH CAROLINA AHEC Epidemiology in Action    Outbreak and Cluster Investigations Public Health Surveillance Community Screening Programs SOUTH CAROLINA AHEC Outbreaks and Clusters   Outbreak: an epidemic limited to a localized increase in the incidence of a disease 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 SOUTH CAROLINA AHEC Characteristics of Outbreak Investigations      Infectious disease or condition Etiologic agent is transmissible organism Short time frame for investigation (hours, days) Moderate to large effect estimates Moderate to high exposure levels SOUTH CAROLINA AHEC Characteristics of Outbreak Investigations, cont.     Acute exposure period (hours, days) Laboratory confirmation common Moderate to high possibility of establishing cause and effect Most common study design: retrospective cohort SOUTH CAROLINA AHEC Characteristics of Cluster Investigations      Non-infectious disease or condition Often unknown or combined etiologic agents Longer time frame for investigation (weeks or months) Weak to moderate effect estimates Low exposure levels SOUTH CAROLINA AHEC Characteristics of Cluster Investigations, cont.     Chronic exposure period (years or decades) Laboratory confirmation uncommon Low possibility of establishing cause and effect Most common study design: casecontrol SOUTH CAROLINA AHEC Challenges of Cluster Investigations     Active or passive approach Epidemiology or public health education Data sources and denominators Costs and yields SOUTH CAROLINA AHEC Public Health Surveillance   Ongoing systematic collection, analysis and interpretation of outcome-specific health data Closely integrated with the timely dissemination of those data to those responsible for preventing and controlling disease or injury SOUTH CAROLINA AHEC Sources of Surveillance Data        Reports of health events Reporting from laboratories Registries Vital statistics Periodic surveys Information on environmental exposures Information from other organizations SOUTH CAROLINA AHEC Uses of Surveillance Information    Immediate detection Annual dissemination Archival information SOUTH CAROLINA AHEC Community Screening Programs     Defining the target population Setting priorities among diseases and conditions Choosing effective screening tests Assessing the effectiveness of screening programs SOUTH CAROLINA AHEC Screening Tests Disease Status Test Results Positive Negative Total Positive Negative Total A B true (+) false (+) C D false (-) true (-) A+C B+D A+B C+D SOUTH CAROLINA AHEC Hypothetical Example Disease Status Test Results Positive Negative Total Positive Negative 900 100 1,000 4,950 94,050 99,000 Total 5,850 94,150 100,000 SOUTH CAROLINA AHEC Sample Data    AIDS Syphilis Diabetes SOUTH CAROLINA AHEC Estimated Incidence of AIDS and Deaths of Adults with AIDS*, 1985 - June 1998, United States 25,000 Number of Cases/ Deaths AIDS Deaths 1993 definition implementation 20,000 15,000 10,000 5,000 0 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Quarter-Year of Diagnosis/Death *Adjusted for reporting delays SOUTH CAROLINA AHEC AIDS Cases by Age and Sex Reported 1981-1998, United States 35,000 30,000 Number of Cases 25,000 20,000 15,000 10,000 Male N=574,783 Female N=113,414 5,000 0 0 10 20 30 40 50 60 70 SOUTH CAROLINA 3 80 90 Age at Diagnosis AHEC Estimated Number of Persons Living with AIDS 1993 -1998, by Sex, United States 250 200 Men Thousands 150 100 50 0 1993 Women 1994 1995 1996 1997 SOUTH CAROLINA 1998 Year AHEC Estimated Number of Persons Living with AIDS 1993 - 1998, by Race/Ethnicity, United States 140 120 Thousands 100 80 60 White, not Hispanic Black, not Hispanic Hispanic 40 20 0 1993 Asian/Pacific Islander 1994 1995 1996 American Indian/ Alaska Native 1997 SOUTH CAROLINA 1998 Year AHEC Estimated Number of Persons Living with AIDS 1993 - 1998, by Race/Ethnicity, United States 2,500 2,000 Persons Asian/Pacific Islander American Indian/ Alaska Native 1,500 1,000 500 0 1993 1994 1995 1996 1997 SOUTH CAROLINA 1998 Year AHEC Estimated Number of Persons Living with AIDS 1993 -1998, by Region, United States 12 0 10 0 Thousands 8 0 South Northeast 6 0 4 0 2 0 0 West Midwest U.S. dependencies and possessions 1994 1995 1996 1997 SOUTH CAROLINA 1993 1998 Year AHEC Proportion of AIDS Cases, by Race/Ethnicity Year of Report,1985-1998, United States 70 60 White, not Hispanic Black, not Hispanic Hispanic Asian/Pacific Islander American Indian/ Alaska Native 1985 1987 1989 1991 1993 1995 SOUTH CAROLINA Percent of Cases 50 40 30 20 10 0 1997 Year of Report AHEC AIDS Cases by Exposure Category and Year of Report, 1985-1998, United States 80 70 Percent of Cases Men who have sex with men (MSM) 60 50 40 30 20 10 Injection drug use (IDU) Heterosexual contact MSM & IDU 1985 1987 1989 1991 1993 1995 1997 0 Year of Report Excludes cases with other or unreported risk pending medical record review and reclassification. SOUTH CAROLINA AHEC AIDS Rates per 100,000 Population Reported in1998 7.8 3.3 6.2 2.6 1.2 14.8 6.6 17.3 4.3 2.6 10.8 4.8 8.1 13.8 12.0 8.5 8.0 15.1 11.1 16.9 20.1 21.8 4.7 13.5 36.5 7.1 12.8 8.2 6.1 0.9 4.0 2.0 3.9 7.3 3.4 VT 2.5 NH MA RI CT NJ DE MD DC 3.5 15.0 12.9 20.3 26.3 23.4 31.9 189.1 47.9 14.5 4.7 7.9 14.7 10.4 20.3 Rate per 100,000 <5 5 - 14.9 15+ PR 44.3 VI 29.6 SOUTH CAROLINA AHEC AIDS Cases Reported in 1998 and Estimated 1998 Population, by Race/Ethnicity, United States AIDS Cases N=48,269* 33% <1% 1 % Population 71% 1 % 4 % N=274,766,00 45% 20% 13% 12% White, not Hispanic Black, not Hispanic Hispanic *Includes 211 persons with unknown race/ethnicity Asian/Pacific Islander American Indian/ Alaska Native SOUTH CAROLINA AHEC 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* Cases 14,027 14,740 7,511 329 117 36,886 Rate 18 125 58 9 16 34 AHEC * Includes 162 men whose race/ethnicity is unknown. SOUTH CAROLINA AIDS by Region & Size of Place of Residence Reported in 1998, United States Metropolitan area 500,000 population % Northeast N=14,399 North Central N=4,317 South N=19,474 West N=8,121 NonMetropolitan metropolitan area 50,000499,999 population area % 4.5 % 2.4 93.1 76.3 14.4 9.3 75.6 86.7 13.5 8.2 SOUTH CAROLINA 10.9 5.0 AHEC Primary and secondary syphilis - Rates by state: United States and outlying areas, 1997 0.3 0.0 0.3 0.1 0.0 0.3 0.1 0.3 1.7 0.2 0.0 0.6 1.2 3.0 Guam 0.0 1.6 2.0 0.1 0.8 1.0 0.2 3.7 2.6 2.1 0.2 0.4 1.1 0.5 3.5 3.5 0.2 0.1 3.5 9.8 14.0 6.9 10.2 Rate per 100,000 population 14.4 9.6 7.0 <4 (n=42) 8.4 4.1-12 (n=7) > 12 (n=3) 2.1 3.5 Puerto Rico 6.7 Virgin Is. 1.8 VT NH MA RI CT NJ DE MD 0.0 0.0 1.3 0.2 1.9 1.9 3.0 17.6 Note: The total rate of primary and secondary syphilis for the United States and outlying areas (including Guam, Puerto Rico, and Virgin Islands) was 3.3 per 100,000 population. The Healthy People year 2000 objective is 4.0 per 100,000 population SOUTH CAROLINA AHEC Primary and secondary syphilis - Counties with rates above and counties with rates below the Healthy People year 2000 objective: United States, 1997 Rate per 100,000 population <4 (n=2,702) >4 (n=413) SOUTH CAROLINA AHEC SOUTH CAROLINA AHEC SOUTH CAROLINA AHEC SOUTH CAROLINA AHEC SOUTH CAROLINA AHEC SOUTH CAROLINA AHEC