What is quality of life?

Introduction

Quality of life is a multidimensional concept encompassing several subcategories. Life satisfaction, well-being, happiness, meaning, and economic indices are but a few of the components of the broader concept of quality of life (QOL), yet no concept alone can adequately capture the complexity of quality of life. Instruments designed to measure QOL permit individuals to assess their overall health subjectively rather than using purely objective medical assessments such as body temperature or weight gain or loss. QOL questionnaires are generally either generic or illness specific; administering both types presents a more complete picture than using either alone.

Because QOL represents both a subjective and objective rating of a person’s overall health and well-being, researchers or medical personnel are able to use it to capture an encompassing view of a single individual, groups or cultures, or entire nations. QOL is often used in scientific research to assess overall health as it relates to other variables of interest (for example, QOL after chemotherapy). Some of the areas where QOL is most frequently examined are health QOL, economic QOL, and specific illnesses and QOL.

Health QOL

Perhaps the most widely investigated area of QOL involves the various facets that make up overall health. Health quality of life (HQOL) questionnaires measure a number of subcategories that are related to general health and well-being, broadly defined: limitations in physical and social activities, limitations in usual role activities because of physical health problems, bodily pain, general mental health (psychological distress and well-being), limitations in usual role activities because of emotional problems, vitality (energy and fatigue), and general health perceptions.

HQOL’s importance, especially in an aging society, is in determining quality-adjusted life years (QALYs), which measure QOL as a person’s age increases. This measure emphasizes living in health and independently instead of just the number of years added to a person’s life. Overall health is not just the absence of illness but includes ensuring that life’s meaning and richness continue with advancing age.

The difference between subjective and objective ratings of HQOL can be quite startling at times; examinations of fatigue is one such example. Two individuals can report the same overall level of fatigue yet report differing levels of fatigability, or how fatigue affects their daily lives. For example, one individual may retain an active and meaningful life, despite suffering great fatigue, whereas another individual, suffering the same fatigue, may be homebound. HQOL begins to unravel this heretofore neglected aspect of patient expectations. This disparity in subjective versus objective ratings is more pronounced when examining the aging population. Despite multiple comorbidities, most seniors report their health as good or better. Shoring up these discrepant ratings is an important contribution of HQOL measurements.

Economic QOL

Determining economic QOL generally involves assessing the gross domestic product (GDP), or total market value of all goods and services produced in a country in a given period (usually a year), and the material well-being of individuals within a culture or nation, which is often referred to as the standard of living. Other QOL indices are the Economist Intelligence Unit’s (EIU) quality-of-life index and human development index, which represent numerous health factors of a country, such as GDP, life expectancy, employment rate, and political stability. Accurately measuring economic QOL is quite important. Often outcomes from such research structure public policy, legislation, and community-based programs, and because wealth creation does not always lead to concomitant increases in overall QOL, it is imperative that a multipronged assessment approach is used to create any economic QOL rating.

In 2008, the United States ranked thirteenth, out of 111 countries, in the EIU quality-of-life index. GDP usually explains around 50 percent of country variation in life satisfaction, suggesting factors other than income affect QOL ratings. Ireland, for example, has the number-one rating despite having low scores in health and climate. In Ireland, family cohesiveness and intact communities increase the nation’s overall QOL. Education level, often a predictor of income, shows a modest correlation with life satisfaction; this finding reinforces the subjective nature and variation among what adds quality to life. In 2012, the EIU published its "Where-to-Be-Born Index, 2013," which ranked Switzerland as the number one place to be born out of eighty countries; the United States was ranked sixteenth.

Specific Illnesses and QOL

Assessing QOL has long been of interest to researchers and clinicians examining patients’ subjective ratings of their health before and after treatment for specific diseases. Because illness-specific QOL questionnaires can demonstrate treatment effectiveness, a growing concern of researchers, clinicians, and insurance companies, their use has increased significantly in the clinical setting. In one study, newly diagnosed lung cancer patients with lower socioeconomic status reported lower health-related QOL, but the differences disappeared at follow-up, suggesting that improved QOL can, in fact, be an outcome of treatment.

Often the effectiveness of treatment is gauged solely on the patient’s self-reported QOL; for example, chemotherapy might have been marginally successful in tumor reduction, but if the patient reports a higher QOL, clinicians will gauge the treatment to be a success. Patients undergoing two different types of colorectal surgery, one widely accepted as superior in objective results, produced identical QOL ratings postsurgery. These often confounding results have pushed assessing patients’ perceptions of the impact of their disease and its treatment on their lives to the top of clinical treatment paradigms.

The Future of QOL

Because culture, expectancies, personality, and many other factors can affect individual ratings of QOL, clinical and research investigations are continually in flux, each searching for the most valid and reliable methods to capture QOL. Emerging research is focusing on ecological momentary assessments, or tracking QOL ratings randomly throughout the day via portable electronic devices, such as cell phones or personal digital assistants (PDAs). At random points throughout the day, a chime sounds, prompting the individual to answer a question about his or her current mood or state (for example, “Right now, are you experiencing any body pain?”). Such real-world data collection allows researchers to track QOL subcategories throughout the day to determine stability and fluctuations of health variables of interest. As personality, expectancies, self-efficacy, and other social cognitive factors can influence QOL, it is paramount that new and innovative ways are continually designed to capture this complex concept.

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