Indicators for Chronic Disease Surveillance

Prepared collaboratively by
CDC, the Council of State and Territorial Epidemiologists, and the Association of State and Territorial Chronic Disease Program Directors

The material in this report originated in the National Center for Chronic Disease Prevention and Health Promotion, James S. Marks, M.D., M.P.H., Director, and the Division of Adult and Community Health, Virginia S. Bales Harris, M.P.H., Director.

Summary

Chronic diseases account for seven of the 10 leading causes of death in the United States, including the three leading causes of preventable death (tobacco use, improper diet and physical inactivity, and alcohol use). Seventy percent of health-care costs in the United States are for chronic diseases. In 1999, to allow public health officials to uniformly define, collect, and report chronic disease data, the Council of State and Territorial Epidemiologists released Indicators for Chronic Disease Surveillance. The report provided standard definitions for 73 indicators developed by epidemiologists and chronic disease program directors at the state and federal level. The indicators were selected because of their importance to public health and the availability of state-level data. This report describes the latest revisions to the chronic disease indicators. The revised set of 92 indicators includes 63 indicators that were unchanged from the first edition, six that have been revised, and 23 that are new. Four indicators from the first edition were deleted. Of the indicators, 24 are for cancer; 15 for cardiovascular disease; 11 for diabetes; seven for alcohol; five each for nutrition and tobacco; three each for oral health, physical activity, and renal disease; and two each for asthma, osteoporosis, and immunizations. The remaining 10 indicators cover such overarching conditions as poverty, education, life expectancy, and health insurance. Additional information regarding the indicators for chronic disease surveillance is available at http://www.cdc.gov/nccdphp/cdi.

Introduction

During the 20^th century, the leading causes of death in the United States shifted from infectious to chronic diseases. Chronic diseases (e.g., cardiovascular disease, cancer, and diabetes) are now among the most prevalent, costly, and preventable of all health problems. Seven of every 10 U.S. residents who die each year (>1.7 million persons) do so as a result of a chronic disease. Chronic diseases affect the quality of life of 90 million U.S. residents (1), and the cost of medical care for persons with these diseases accounts for 70% of total medical care expenditures (2).

Although chronic diseases are among the most common and costly health problems, they are also among the most preventable. Adopting healthy behaviors (e.g., eating nutritious foods, being physically active, and avoiding tobacco use) can prevent or control the effects of these diseases. In addition, quality of life is enhanced when chronic diseases are detected and treated early. Regular screening can reduce morbidity and mortality from cancers of the breast, cervix, colon, and rectum. Clinical preventive services can prevent the debilitating complications of diabetes and cardiovascular disease.

Increased chronic disease mortality and greater opportunities for primary and secondary prevention of chronic disease have resulted in an expansion of chronic disease programs in state public health agencies. Community intervention programs have proved to be effective, and certain ones have become model programs for public health (3,4). Within the past decade, each state has developed programs in tobacco control and breast and cervical cancer control.

Comprehensive public health programs necessarily include monitoring of disease or risk factors through public health surveillance, which is defined as the ongoing systematic collection, analysis, and interpretation of outcome-specific data for use in planning, implementing, and evaluating public health practice (5). Multiple data systems form the foundation for chronic disease surveillance. Chronic disease surveillance initially focused on mortality data from the National Vital Statistics System, managed by CDC's National Center for Health Statistics. However, in the 1970s, morbidity from selected chronic diseases came under surveillance through disease registries. For example, the National Cancer Institute established the Surveillance, Epidemiology, and End Results cancer registry system to record and follow every new case of cancer among nine specific U.S. populations, four of which were states. In 1992, Congress authorized the National Program of Cancer Registries (NPCR) at CDC to monitor local trends in cancer incidence and mortality with statewide, population-based cancer registries.

In the 1980s and 1990s, CDC and state health agencies collaboratively developed additional surveillance systems to monitor behavioral risk factors for chronic disease. In 1984, with CDC assistance, 15 state health agencies began to use the Behavioral Risk Factor Surveillance System (BRFSS) to monitor adult behaviors related to the leading causes of death. Recognizing the usefulness and flexibility of BRFSS, all 50 states, the District of Columbia, and three territories participated in the system by 1994. By 2003, a total of 43 states and 22 local areas (also supported with financial and technical assistance from CDC) used the Youth Risk Behavioral Surveillance System (YRBSS) to monitor health risk behaviors among high school students.

Abbreviations Used in This Report

Chronic Disease Indicators

In 1996, the Council of State and Territorial Epidemiologists (CSTE) voted to place the prevalence of cigarette smoking among adults, data for which were collected for each state by BRFSS, under nationwide surveillance. This was the first time that CSTE --- the professional organization that, in conjunction with CDC, has historically reviewed and recommended procedures for nationwide, state-based surveillance --- had placed a personal behavior associated with a chronic disease under nationwide surveillance. This action effectively defined the first indicator for chronic disease surveillance. In addition, this was the first time that a survey sample was designated as the mechanism by which surveillance data would be used for nationwide, state-level surveillance.

Although conducting nationwide surveillance for prevalence of cigarette smoking among adults was important, it made CSTE, the chronic disease directors (CDD), and CDC more aware of the lack of a comprehensive and consistent approach to state-level chronic disease surveillance. For example, no guidelines existed for state-level surveillance of other behavioral risks (e.g., physical inactivity or unhealthy eating). Similarly, state-level epidemiologists did not necessarily employ consistent methods to report chronic diseases and risk factors. For example, epidemiologists from different states might have been using the 1940 U.S. population, the 1970 U.S. population, or a population of their own state for standardization of rates.

To address the need for common definitions and methods for state-level chronic disease surveillance, CSTE, CDD, and CDC collaborated in a 2-year process that led CSTE to adopt 73 chronic disease indicators (CDI) (6). The 73 indicators were chosen because 1) the disease or condition being monitored by the indicator incurred a substantial public health burden, and 2) surveillance data were available for the majority of states. The indicators provided 1) a minimal set of chronic diseases, conditions, and risk factors that would be under state-level surveillance; 2) consistent methods for state-level analyses, results from which would provide comparable state-specific data; and 3) an operational measure of state-level capacity in chronic disease surveillance, with a state's successful use of the indicators being one benchmark of the state's efforts in chronic disease surveillance.

In 2001, CSTE, CDD, and CDC began revising the chronic disease indicators. Chronic disease epidemiologists, program managers, subject matter experts, and partner organizations met to review existing indicators and to propose a revised set of indicators. Proposed indicators were evaluated for their relevance to chronic disease prevention and control at the state level and for the availability of data on an annual or biannual basis at the state level for the majority of states. In addition, an attempt was made to select indicators that were consistent with Healthy People 2010 objectives (7). At the 2002 annual meeting, CSTE membership approved a revised set of 92 chronic disease indicators (Table) (see Appendix). This report describes how each indicator is to be measured, why it is important, the limitations for both the indicator and its data source, and the relevant objective in Healthy People 2010 (7).

Data Sources

Data for surveillance of chronic disease indicators are derived from multiple sources.

• Behavioral Risk Factor Surveillance System. BRFSS, a major source of data, is a telephone survey conducted by all state health departments, the District of Columbia, Puerto Rico, the Virgin Islands, and Guam with assistance from CDC. BRFSS is the largest continuously conducted telephone health survey in the world, monitoring preventable chronic diseases, injuries, and infectious diseases. States use BRFSS data to track health problems and to develop and evaluate public health programs. Data are collected by using standard procedures through monthly telephone interviews with adults aged >18 years (8).
• Cancer Registries. State cancer registries collect information about the incidence of cancer, the types of cancers that occur and their locations within the body, and the extent of cancer at the time of diagnosis. These data are reported to a central statewide registry from different medical facilities, including hospitals, physicians' offices, therapeutic radiation facilities, freestanding surgical centers, and pathology laboratories. CDC's NPCR provides funds to 45 states, three territories, and the District of Columbia to enhance state-level cancer registries and data analysis (9). NPCR works with the North American Association of Central Cancer Registries (NAACCR) to develop and implement surveillance methods and protocols.
• Current Population Survey. The Current Population Survey (CPS) is the primary source of information on the labor force characteristics of the U.S. population. The sample is scientifically selected to represent the civilian noninstitutional population. Estimates obtained from CPS include employment, unemployment, earnings, hours of work, and other indicators, and are available by different demographic characteristics, including age, sex, race, marital status, and educational attainment (10).
• Hospital Discharge Data. Hospital discharge data are the abstracted records associated with a patient's stay in a short-term hospital. These data typically contain diagnosis, treatment, and payment information. State-based hospital discharge data are collected, maintained, and analyzed by individual states. Hospital discharge data for Medicare beneficiaries are handled by the Centers for Medicare and Medicaid Services (CMS).
• Death Certificates. In the United States, state laws require death certificates to be completed for all deaths, and federal law mandates national collection and publication of deaths and other vital statistics data. The National Vital Statistics System is the result of the cooperation between CDC and the states to provide access to statistical information from death certificates. Mortality data are used to monitor the underlying and contributing causes of death for persons dying in the United States and to determine life expectancy (11).
• Tobacco Data Sources. The State Tobacco Activities Tracking and Evaluation (STATE) System is an electronic data warehouse containing up-to-date and historic state-level data on tobacco use prevention and control. The STATE System is designed to integrate multiple data sources, provide comprehensive summary data, and facilitate research with consistent interpretation of data (12). State revenue agencies are an alternative source of information on state tobacco sales.
• Renal Disease Data Sources. The United States Renal Data System (USRDS) is a national data system that collects, analyzes, and distributes information about end-stage renal disease (ESRD) in the United States. USRDS is funded directly by the National Institute of Diabetes and Digestive and Kidney Diseases in the National Institutes of Health, in conjunction with CMS. USRDS staff collaborate with members of CMS and the ESRD networks to share data sets and improve the accuracy of ESRD patient information (13).
• Youth Risk Behavior Surveillance System. YRBSS monitors priority health risk behaviors that contribute markedly to the leading causes of death, disability, and social problems among youth and adults in the United States. These behaviors, often established during childhood and early adolescence, include tobacco use, unhealthy dietary behaviors, inadequate physical activity, alcohol and other drug use, risky sexual behaviors, and behaviors that contribute to unintentional injuries and violence. Conducted as a school-based survey every 2 years, YRBSS includes national, state, and local representative samples of students in grades 9--12 (14). For states that do not participate in YRBSS, the Youth Tobacco Survey (YTS) can provide data on the prevalence of tobacco use among high school students.

Data Concerns

Certain concerns related to data analysis should be considered when using the chronic disease indicators. To be comparable, standardized chronic disease indicator rates should use the same standard population figures. In 1999, the U.S. Department of Health and Human Services began to adjust all mortality data to the year 2000 U.S. standard population to enhance the comparability of disease rates for different geographic areas and subpopulations. Whenever possible, rates for chronic disease indicators should be standardized to the year 2000 U.S. population. Because the age of the population being monitored is not the same for all indicators, each indicator that calls for an age-standardized measure has a particular age distribution to be used in the standardization process (15).

Certain agencies and professional organizations have established thresholds for the quality of data. For example, NAACCR has calculated combined incidence rates only for data from cancer registries of the highest quality, as demonstrated by compliance with all requests and standards related to completeness and quality. Also, CDC only weights YRBSS data to produce state-specific estimates for surveys that have an overall response rate of >60% and have appropriate survey documentation. In addition, because surveillance that is based on a limited number of cases in a defined geographic area or demographic group might compromise a person's confidentiality, public health agencies often do not publish surveillance reports or summary information that is based on less than a specific number (e.g., five) of cases. The threshold for publishing data might also depend on the geographic level and size of the population for which the data are reported.

Another concern is that rates based on limited numbers are inherently unstable. For example, if five persons among a population of 10,000 have a particular chronic disease and six persons among another population of 10,000 have the same disease, the rate among the second population is 1.2 times higher. However, the 20% increase is from only one additional case; such variations can be within the expected random fluctuation of disease occurrence.

Finally, to partially adjust for potential nonresponse and sample selection bias, sample surveys (e.g., BRFSS and YRBSS) typically weight their data. The weights are estimates of the population by subgroup (e.g., age, race, or sex) from which the survey data were collected.

Future Needs

The indicators should be reviewed periodically because of changes in availability of data and public health priorities for chronic disease. Surveillance data sources at the state level should also be improved. For example, multiple states do not participate in YRBSS or have access to hospital discharge data. Finally, not all states have sufficient chronic disease epidemiology capacity to collect, analyze, and report on the data required for each indicator. Fifteen (30%) states and the District of Columbia do not report having a state chronic disease epidemiologist (16).

References

1. CDC. Chronic disease prevention. Atlanta, GA: US Department of Health and Human Services, CDC, National Center for Chronic Disease Prevention and Health Promotion, 2004. Available at http://www.cdc.gov/nccdphp.

2. CDC. The burden of chronic diseases and their risk factors: national and state perspectives. Atlanta, GA: US Department of Health and Human Services, CDC, 2004.

3. American Cancer Society, Association for Healthcare Quality Research, CDC, National Cancer Institute, Substance Abuse and Mental Health Services Administration. Cancer control PLANET: links to resources for comprehensive cancer control. Available at http://cancercontrolplanet.cancer.gov.

4. Task Force on Community Preventive Services. Guide to community preventive services. Atlanta, GA: US Department of Health and Human Services, CDC, 2003. Available at http://www.thecommunityguide.org.

5. Thacker S. Historical development. In: Teutsch S, Churchill R, eds. Principles and practice of public health surveillance. 2^nd ed. New York: Oxford University Press, 2000.

6. Lengerich EJ, ed. Indicators for chronic disease surveillance: consensus of CSTE, ASTCDPD, and CDC. Atlanta, GA: Council of State and Territorial Epidemiologists, 1999.

7. US Department of Health and Human Services. Healthy People 2010. 2^nd ed. With understanding and improving health and objectives for improving health (2 vols.). Washington DC: US Department of Health and Human Services, 2000.

8 CDC. Behavioral Risk Factor Surveillance System: turning information into health. Atlanta, GA: US Department of Health and Human Services, CDC, 2004. Available at http://www.cdc.gov/brfss.

9. CDC. National program of cancer registries. Atlanta, GA: US Department of Health and Human Services, CDC, National Center for Chronic Disease Prevention and Health Promotion, 2004. Available at http://www.cdc.gov/cancer/npcr.

10. Bureau of Labor Statistics, Bureau of the Census. Current population survey. Washington, DC: US Department of Labor, US Census Bureau, 2001. Available at http://www.bls.census.gov/cps/cpsmain.htm.

11. CDC. Mortality data from the national vital statistics system. Hyattsville, MD: US Department of Health and Human Services, CDC, National Center for Health Statistics, 2004. Available at http://www.cdc.gov/nchs/about/major/dvs/desc.htm.

12. CDC. STATE: State Tobacco Activity Tracking & Evaluation System. Atlanta, GA: US Department of Health and Human Services, CDC, National Center for Chronic Disease Prevention and Health Promotion. Available at http://www2.cdc.gov/nccdphp/osh/state.

13. USRDS Coordinating Center. USRDS: United States Renal Data System. Minneapolis, MN: USRDS Coordinating Center, 2004. Available at http://www.usrds.org.

14. CDC. Youth Risk Behavior Surveillance System. Atlanta, GA: US Department of Health and Human Services, CDC, National Center for Chronic Disease Prevention and Health Promotion, 2004. Available at http://www.cdc.gov/yrbs.

15. Klein RJ, Schoenborn CA. Age adjustment using the 2000 projected U.S. population. Hyattsville, MD: US Department of Health and Human Services, CDC, National Center for Health Statistics, 2001. Healthy people 2010 statistical notes, no. 20.

16. Council of State and Territorial Epidemiologists. Current state chronic disease epidemiologists. Atlanta, GA: Council of State and Territorial Epidemiologists, 2004. Available at http://www.cste.org/surveys/scdesurveyresultreviewList.asp.

Chronic Disease Indicators Working Group

June 2004

Mark Baptiste, Ph.D., and Ursula Bauer, Ph.D., New York State Department of Health; Katrina Hedberg, M.D., Oregon Department of Human Services; Gary Hogelin (retired), M.P.H., Andrew Pelletier, M.D., and Paul Z. Siegel, M.D., CDC; Donna Kephart, M.H.A., and Eugene Lengerich, V.M.D., Pennsylvania State University; Donna Knutson, M.S.Ed., LaKesha Robinson, M.P.H., and Shah Roohi, Council of State and Territorial Epidemiologists; John Kurata, M.D., California State Department of Health Services; and Adeline Yerkes, M.P.H., Oklahoma State Health Department.

Chronic Disease Indicators: Physical Activity and Nutrition

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