CENTERS FOR DISEASE CONTROL AND PREVENTION
Volume 16 • Number 2/3 • Winter/Spring/Summer 2004

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Measuring Quality of Life in the World, Nation, States, and Local Areas

Interest in CDC’s Healthy Days measures has grown as health-related quality of life indicators are recognized as useful tools for identifying populations at risk, health disparities among subgroups, and resource needs in public health planning. Here are some reports that use these or similar measures.

World
United Nations’ Human Development Report 2003. The most and least livable countries are ranked by their citizens’ quality of life. Quality of life is defined by life expectancy, educational attainment, and adjusted real income. Visit http://www.undp.org/hdr2003/.*

Nation and States
America’s Health: State Health Rankings (2003 Edition). Produced by the United Health Foundation in partnership with the American Public Health Association (APHA) and the Partnership for Prevention, the report ranks the healthiness of each state’s population based on 16 measures of health, including the recent activity limitation days data from CDC’s Behavioral Risk Factor Surveillance System (BRFSS). Visit http://www.unitedhealthfoundation.org/shr2003/.*

2000 and 2001 State Women’s Health Report Cards
Making the Grade on Women’s Health: A National and State-by-State Report Card is the first report to assess comprehensively the overall health of women at the state and national levels. Visit the National Women’s Law Center Web site at http://www.nwlc.org/display.cfm?section=health.*

Kaiser Family Foundation’s State Health Facts Online. This new resource contains the latest state-level data on demographics, health, and health policy, including health coverage, access, financing, and state legislation. Data on all 50 states can be compared by 11 topics, which include demographics, health status, health coverage, managed care, and health costs. To view a profile of a particular state, click on a map, then select a topic. The information is user-friendly and comprehensive. See state comparisons on mental health, including data from the BRFSS on recent mental health. Visit http://www.statehealthfacts.kff.org/.*

Cities, Counties, and Communities
Improving Health in the Community. This important publication from the Institute of Medicine (IOM) describes the use of community indicators and performance monitoring to improve community health. The guide also provides tools to help communities develop their own performance indicators. CDC’s Healthy Days measures are included among the IOM’s suggested community performance indicators. Visit http://www.nap.edu/catalog/5298.html.*

Community Health Status Indicators Project
(http://www.phf.org/data-infra.htm)
The Community Health Status Indicators (CHSI) Project has produced a county-specific report of community health status for local jurisdictions across the United States. The project’s goal was to provide important health and health-related data, presented in a way that makes them useful to communities. This collaborative activity of the Association of State and Territorial Health Officials, the National Association of County and City Health Officials, and the Public Health Foundation was initially funded by the Health Resources and Services Administration (HRSA) and is currently being updated with additional support from CDC and the Agency for Toxic Substances and Disease Registry (ATSDR).

National Neighborhood Indicators Partnership
This collaborative effort by the Urban Institute and local partners is intended to improve neighborhoodlevel information systems for use in local policy making and community building. The Web site (http://www.urban.org/nnip/*) also provides a number of useful publications and links to other sites related to indicators and community building.

Knox County,Tennessee, Health-Related Quality of Life Report (July 2003)
This state of the county report highlights mental health as an area with possibilities for public health intervention. Visit http://www.knoxcounty.org/health/hrql03.pdf.*

 
CDC Offers Resources on Conducting and Interpreting Economic Evaluations

Whether you plan to conduct your own economic evaluations or interpret the results of evaluations done by experts in the field, CDC offers assistance.

Interactive Course
CDC has developed a free, interactive, Web-based course on economic evaluations. Prevention Effectiveness: Decision Analysis and Economic Evaluation covers the basics of decision analysis and economic evaluation methods, using case studies and modules focusing on topics such as cost-benefit analysis, cost-utility analysis, cost-effectiveness analysis, and sensitivity analysis. The goals of the course are to help practitioners plan and conduct their own prevention-effectiveness studies and interpret the results of studies conducted by others.

“We hope that taking this course will lead to more states collecting cost data,” noted Vilma G. Carande-Kulis, PhD, lead economist and chief of CDC’s Prevention Effectiveness Branch. “States have to know not only how effective the interventions are but how efficient they are. And if you’re going to measure economic efficiency, you have to not only measure health-related quality of life but also start measuring costs. That, in turn, would help states make better use of the resources they have.” For more information about the course, contact Dr. Carande-Kulis at VCarande-Kulis@cdc.gov.

Checklist for Assessing Studies
For states that don’t plan to conduct their own economic evaluations but simply want to be better able to scrutinize the studies already out there, some advice and resources are available from Ping Zhang, PhD, and Michael M. Engelgau, MD, of CDC’s diabetes program. They suggest questions state health departments ask the following to determine if an economic analysis was well conducted and its results are valid and reliable.

• Was the study question well defined? The study question should clearly identify the alternatives being compared and the viewpoints from which the comparisons were made.
• Was a comprehensive description of a competing alternative given? A good study should provide a clear and specific statement of the primary objective of each alternative program. This information allows readers to judge the applicability of the program to their own setting.
• Were all the important and relevant costs and consequences for each alternative identified? Even though it might not be possible or necessary to measure and value all of the costs and consequences of the alternatives under comparison, the study should fully identify the important and relevant ones.
• Were costs and consequences adjusted for differential timing? Because a comparison of programs must be made at one point in time (usually the present), the timing of program costs and consequences that do not occur entirely in the present time must be adjusted to reflect current values. Both costs and health consequences such as quality-adjusted life years, which occur in the future, should be discounted back to their present values at the social discount rate. The U.S. Panel on Cost-Effectiveness in Health and Medicine recommends a 3% annual discount rate.
• Was an incremental analysis of costs and consequences of each alternative performed? To allow meaningful comparisons, the study needs to examine the additional costs that one program imposes over another, compared with the additional effects, benefits, or utilities that the program delivers.
• Was allowance made for uncertainty in estimates of costs and consequences? Lack of data, data generated from different settings, and different views on how to handle a study problem are common problems in the economic evaluation of health interventions. Therefore, the study needs to examine how these uncertainties, imprecise uses of data, or methodological controversies might affect the study conclusion.

“We encourage you to use and interpret the studies already out there and use them to make informed decisions about what you’re going to do,” recommended Dr. Engelgau. “They won’t make the decisions for you, but they are a useful tool and just one piece of the puzzle to consider when making decisions about how to allocate resources.”

 
Population Health and Quality of Life Measures Designed for Different Purposes

Many health-related quality of life measures are available, and each is designed to meet specific purposes:

• To measure the burden of disease, monitor the health status of a population over time, and track progress in meeting health objectives.
• To determine the cost-effectiveness of one intervention or compare the cost-effectiveness of several different interventions.
• To identify populations affected by health disparities.
• To evaluate interventions targeting specific diseases or conditions.
• To identify health priorities and guide the development of health policies.

By measuring and tracking health-related quality of life (HRQOL), researchers can identify people who would benefit the most from healthier environments, early diagnosis of disease, and treatment. The findings are also valuable in predicting which people are most at risk of dying, requiring hospitalization, or needing outpatient services over the next year. Here are just some of the measures being used around the world to collect and analyze data on health status and health-related quality of life.

Quality of Well-Being Scale
The Quality of Well-Being Scale is a self-administered questionnaire that measures how disease and disability affect people’s ability to function physically, take care of themselves, and engage in social activities. People select from various scenarios that describe their function level (mobility, physical activity, social activity) and symptoms or problems that might impair their ability to function. With this scale, preference weights are used to integrate the three function levels as well as the symptoms and problems into a single number, ranging from 0 (death) to 1 (perfect health).

Researchers have used the Quality of Well-Being Scale to evaluate outcomes for people with AIDS, arthritis, diabetes, and many other chronic illnesses. The scale has been used in many large studies, including the Diabetes Prevention Program (DPP) clinical trial.

Health Utility Index
This index is used to measure improvements in health. Like the Quality of Well-Being Scale, the Health Utility Index is preferencebased and rates an individual’s health on a scale of 0 (death) to 1 (perfect health). The index also allows researchers to assign negative values to a person with a health status considered worse than death.

The Health Utility Index has been used in population surveys, clinical studies, and cost-effectiveness studies to evaluate public health interventions. This index was one of the tools used in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study.

EQ-5D (EuroQol) Survey
Developed in Europe, the EQ-5D is a preference-based survey that asks people to rate their current health state on a scale ranging from 0 (the worst they can imagine) to 100 (the best they can imagine). The survey asks about mobility; self-care; usual activities such as work, housework, and leisure activities; pain or discomfort; and anxiety or depression.

The EQ-5D is designed to complement other quality of life surveys such as the SF-36. The survey has been used to measure many different health conditions and treatments. It has been used in population surveys and clinical studies. This was one of the tools used in the Translating Research Into Action for Diabetes (TRIAD) and ACCORD studies.

QALYs
A quality-adjusted life year (QALY) is an aggregate measure that takes into account both length of life and quality of life. This preference-based measure estimates the time a person will live at different levels of health over the remaining years of life, with 1 equaling perfect health, and 0 equaling death.

With QALYs, the goal is to determine how many quality-adjusted life years can be gained through a particular intervention. QALYs are often used in cost-utility studies to assess the economic efficiency of interventions and to compare a person’s quality of life with or without a particular intervention.

“QALY weights are applied to various aspects of a person’s physical and mental health to get an overall estimate of that person’s health,” explained CDC program analyst David G. Moriarty, an aging studies specialist who coordinates CDC’s HRQOL assessment program. “You can then average individuals’ scores to get an overall population estimate—say, the 0.85 level of health. QALYs can also tell you how intervention A costs this much but brings you from the current score of 0.85 to only 0.86. Intervention B, on the other hand, costs more but gives you a greater point gain in the score.”

DALYs
Another preference-based measure is the disability-adjusted life year (DALY), which measures the burden of disease and disability in a population. Preference scores, derived from experts worldwide, range from 0 (death) through 1 (perfect health). “Whereas QALYs measure what you would gain by conducting a particular intervention, DALYs measure the health gap between the ideal and what the population is actually experiencing,” explained CDC medical geographer James B. Holt, PhD, MPA.

“DALYs allow for broad standardization of measurements of morbidity across a broad spectrum of diseases and socioeconomic conditions,” noted Vilma G. Carande-Kulis, PhD, lead economist and chief of CDC’s Prevention Effectiveness Branch. DALYs can help guide decisions about allocating health care resources, and they are being used in studies both small and large. For instance, the Los Angeles County Department of Health Services analyzes DALYs and includes the results in its report on disability. The World Health Organization is using DALYs in its Global Burden of Disease project to estimate health-related quality of life among countries.

CDC will soon launch a project to look at geographic variations in DALYS from region to region and to examine trends over time and differences in population groups. “So we’ll be looking at DALYs in different ways—geographically, demographically, and over time,” Dr. Holt noted. The work will be done through a cooperative agreement, which will be funded in fiscal year 2004 over a 3-year period.

“The DALY is not a new measure, and, as with other subjective measures, it has its detractors,” said Dr. Holt, pointing out that some researchers interpret the economic valuation methodology as placing different values on older people than on younger people. DALYs also have raised methodological concerns because of the way in which preference weights are set—by experts and not the population. Nevertheless, “DALYs are there waiting for us to use,” he said. “They will help us plan our program interventions and see where the burden is greatest in terms of disease and disability. We feel DALYs are very useful and will give us information we would otherwise not be able to gather.”

Short Form 36
The Short Form 36, developed and validated in the RAND Corporation’s Medical Outcomes Study, is a questionnaire used by clinicians and researchers around the world. Commonly referred to as the SF-36, this tool uses 36 questions, eight subscales, and two summary scales to assess key aspects of people’s physical and mental health. Individuals are asked to rate their general health, vitality, pain, limitations (due to physical and emotional problems), functioning (physical and social), as well as psychological distress and well-being. Recently, shorter forms of this instrument have been developed.

The SF-36 can be used alone or with disease-specific measures in clinical practice, research, and policy analysis, according to Ping Zhang, PhD, a CDC health economist. The survey can be used for both the general population and patients.

Healthy Days
CDC’s Healthy Days measures differ from the preference-based measures because they are direct estimates of people’s perceived physical and mental health over time. They were designed to identify health disparities and trends and to evaluate changes resulting from broad population-based interventions. CDC worked with many partners to develop this standard set of questions.

The Healthy Days measures tally a person’s responses to determine the number of days during the previous month when he or she felt that either physical or mental health was not good (see calendar, page 37). The Healthy Days measures include four core questions that identify trends over time and reveal how population subgroups are doing compared with the general population. Because the core questions do not provide the details needed to identify public health interventions that might help these individuals, the CDC HRQOL-14 was developed. It includes the 4 core questions plus 10 questions that gather more detailed information on activity limitation and quality of life.

“Tools such as Healthy Days allow public health practitioners to use a common measure to prioritize,” said Charles G. Helmick, MD, a CDC medical epidemiologist specializing in arthritis. “If you think HRQOL is important, these measures will help you see where the biggest problems are, by disease. Measuring health-related quality of life is a good way to set priorities from a broad public health perspective. And it’s a good way of getting at the burden and learning how bad a disease is,” he noted. “Ideally, it is a good way to track changes as a result of our interventions.”

“The Healthy Days questions have been useful in collecting data on arthritis because the questions are concise and can be incorporated into existing surveys,” Dr. Helmick noted. “We were looking for a short version that people would use. If we want our constituents—state health departments —to look at other outcome measures, such as quality of life, we have to make it very easy for them to collect the data.”

The Behavioral Risk Factor Surveillance System (BRFSS) and the National Health and Nutrition Examination Survey (NHANES) have both added the core Healthy Days questions to their surveys and can now provide a wealth of quality of life information on adults with arthritis and other chronic diseases. CDC researchers are eager to analyze the 2000 and later NHANES Healthy Days data because NHANES is the premiere survey for assessing the U.S. population’s health status. NHANES includes a national sample of 5,000–6,000 people each year, and its HRQOL findings will complement the state data collected through the BRFSS.

The Healthy Days measures are not typically used in cost-effectiveness studies because health economists prefer preference-based tools, such as the Health Utility Index and Quality of Well-Being Scale, in which each item is weighted. “Those tools are more in concert with economic theory,” Mr. Moriarty explained. “We’re now trying to gain a better understanding of how our Healthy Days measures are similar to and different from these other measures and how the Healthy Days measures might be adapted for use in costeffectiveness studies.”

“One of the key advantages of tracking population health-related quality of life is that it tells you things you wouldn’t ordinarily see with a point-in-time survey,” said Mr. Moriarty, who has worked for the past decade to develop and test the validity of methods for measuring health-related quality of life. Measuring how people perceive their physical and mental health over time is important “because it’s the foundation that will allow us to study the effects of public policies and a variety of factors, like the environment,” he noted. “But also it will help us identify health disparities that should be further investigated.”

In the future, CDC plans to study how the weather, climate, and seasons affect people’s perceptions of their health, Mr. Moriarty said. The data can also be analyzed to help determine how the economy, the quality of our health systems, air and water pollution, sprawl, and even traffic affect people’s health and quality of life.

Healthy Days = days in the past 30 days when both physical and mental health were good

Such information is useful to health planners and legislators. They can use HRQOL data to evaluate and strengthen public health programs, to compare the cost-effectiveness of various interventions, and to guide their decisions about health policies and allocation of scarce public health resources. HRQOL findings are also used to set health objectives for the nation, states, and communities. The ultimate goal of such research is to promote people’s physical and mental well-being, which, in turn, gives individuals the potential to increase their satisfaction with life, ability to take care of themselves, and ability to engage in social activities.

A multitude of other instruments have been developed to measure health-related quality of life. Good sources on the many tools in use around the world are the Compendium of Quality of Life Instruments by Sam Salek (Wiley, 1999) and the Quality of Life Instruments Database (QOLID), available at http://www.qolid.org.*

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This page last reviewed August 10, 2004

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