74 SECTION 3 Preventive Medicine and Public Health for adaptation to stressors in an individual is called the allo- expectancy on the basis of morbidity, the perceived qualit static load on an individual, and it may be an important of life, or both. Such indices also can be used to help guide contributor to many chronic diseases. linical practice and research. For example, they might show hat a country s emphasis on reducing mortality may not be C. Health as Satisfactory functioning producing equal results in improving the function or self- Often what matters most to people about their health is how perceived health of the country's population. When clini- ey function in their own environment. The inability to with a chronic disease, such as prostate cancer, this approach function at a satisfactory level brings many people to a physi- allows them to consider not only the treatment's impact cian more quickly than does the presence of discomfort mortality but also its side effects, such as incontinence and unctional problems might impinge on a persons ability to impotence. Describing survival estimates in terms of the see,to hear, or to be mobile As Dubos states, " Clearly, health quality of life communicates a fuller picture than survival and disease cannot be defined merely in terms of physiological, or mental attributes. Their real measure is the Life expectancy traditionally is defined as the average ability of the individual to function in a manner acceptable number of years of life remaining at a given age. The metric of which he is a part. breslow of quality-adjusted life years( QALY) incorporates both life describes health as "both(1)the current state of a human perceIved Impact rganism's equilibrium with the environment, often called illness, pain, and disability on the patients quality of life. health status, and (2 )the potential to maintain that balance. For example, a patient with hemiparesis from a stroke might However health is defined, it derives principally from be asked to estimate how many years of life with this dis- forces other than medical care. Appropriate nutrition, ade ability would have a value that equals to I year of life with quate shelter, a nonthreatening environment, support good health(healthy years). If the answer were that 2 limited relationships, and a prudent lifestyle contribute far more to years is equivalent to 1 healthy year, I year of life after a health and well-being than does the medical care system stroke might be given a quality weight of 0.5. If 3 limited Nevertheless, medicine contributes to health not onl ears were equivalent to I healthy year, each limited year through patient care, but also indirectly by developing and would contribute 0 33 year to the QALY. Someone who mu disseminating knowledge about health promotion, disease live in a nursing home and is unable to speak might consider life under those conditions to be as bad as, or worse than no life at all. In this the weighting factor would be 0.0 fe II. MEASURES OF HEALTH STATuS lealthy life expectancy is a less subjective measure that attempts to combine mortality and morbidity into one Measures of health status can be based on mortality, on the index. The index reflects the number of years of life remain pact of a particular disease on quality of life, and on the ing that are expected to be free of serious disease. The onset y to function. Historically, measures of health status of a serious disease with permanent sequelae(e. g, peripheral have been based primarily on mortality data(see Chapter 2). vascular disease leading to amputation of a leg)reduces the Researchers assumed that a low age-adjusted death rate and healthy life expectancy index as much as if the person who high life expectancy reflected good health in a population. has the sequela had died from the disease Another way to account for premature mortality in different Other indices combine several measures of health status age groups is the measure of years of potential life lost The general well-being adjustment scale is an index that YPLL). This measure is used mainly in the field of injury measures"anxiety, depression, general health, positive well prevention In YPLL, deaths will be weighted depending on being, self-control, and vitality. Another index is called the how many years a person might have lived if he or she had life expectancy free of disability, which defines itself. The not died prematurely. This measure gives more weight to U.S. Centers for Disease Control and Prevention(CDC) developed an index called the health-related quality of life Using measures of mortality alone has seemed inadequate based on data from the Behavioral risk Factor Surveillance an increasing proportion of the population in developed System(BRFSS). Using the BRFSS data, CDC investigators and disabling illnesses. An appropriate societal goal is for good to excellent. Also, the e average number of good health people to age in a healthy manner, with minimal disability days(the number of days free of physical and mental health until shortly before death. Therefore, health care investiga problems during the 30-day period preceding the interview) tors and practitioners now show increased emphasis on was 25 days in the adults surveyed improving and measuring the health-related quality of life. Several scales measure the ability of patients to perform Measures of the quality of life are subjective and thus more their daily activities. These functional indices measure activi hallenging to develop than measures of mortality. However, ties that directly contribute to most people's quality of life, efforts to improve the methods for measuring quality of life without asking patients to estimate the quality of life com are ongoing. ared to how they would feel if they were in perfect health An example of such a measure is a health status index. uch functional indices include Katz's activity of daily living A health index summarizes a person's health as a single (ADL) index and Lawton- Brody's instrumental activities of score,whereas a health profile seeks to rate a persons health daily living(IADL)scale. These scales have been used exten on several separate dimensions. Most health indices and sively in the geriatric population and for developmentally profiles require that each subject complete some form of challenged adults. The ADL index measures a peng( eed, and ns abilit questionnaire. Many hea th status indices seek to adjust life independently to bathe, dress, toilet, transfer