In general, quality of life (QoL or QOL) is the perceived quality of an individual’s daily life, that is, an assessment of their well-being or lack thereof. This includes all emotional, social and physical aspects of the individual’s life. In health care, health-related quality of life (HRQoL) is an assessment of how the individual’s well-being may be affected over time by a disease, disability or disorder.^[1][2]

Measurement

Early versions of healthcare-related quality of life measures referred to simple assessments of physical abilities by an external rater (for example, the patient is able to get up, eat and drink, and take care of personal hygiene without any help from others) or even to a single measurement (for example, the angle to which a limb could be flexed).

The current concept of health-related quality of life acknowledges that subjects put their actual situation in relation to their personal expectation.^[3]The latter can vary over time, and react to external influences such as length and severity of illness, family support, etc. As with any situation involving multiple perspectives, patients’ and physicians’ rating of the same objective situation have been found to differ significantly. Consequently, health-related quality of life is now usually assessed using patient questionnaires. These are often multidimensional and cover physical, social, emotional, cognitive, work- or role-related, and possibly spiritual aspects as well as a wide variety of disease related symptoms, therapy induced side effects, and even the financial impact of medical conditions.^[4] Although often used interchangeably with the measurement of health status, both health-related quality of life and health status measure different concepts.

Activities of daily living

Because health problems can interfere with even the most basic aspects of daily living (for example, breathing comfortably, quality of sleep, eliminating wastes, feeding oneself, dressing, and others), the health care professions have codified the concepts of activities of daily living (ADLs) and instrumental activities of daily living (IADLs). Such analysis and classification helps to at least partially objectify quality of life. It cannot eliminate all subjectivity, but it can help improve measurement and communication by quantifying and by reducing ineffability.

Examples

Similar to other psychometric assessment tools, health-related quality of life questionnaires should meet certain quality criteria, most importantly with regard to their reliability and validity. Hundreds of validated health-related quality of life questionnaires have been developed, some of which are specific to various illnesses. The questionnaires can be generalized into two categories:

Generic instruments

• CDC HRQOL–14 “Healthy Days Measure”: A questionnaire with four base questions and ten optional questions used by the Center for Disease Control and Prevention (CDC) (https://www.cdc.gov/hrqol/hrqol14_measure.htm).
• Short-Form Health Survey (SF-36, SF-12, SF-8): One example of a widely used questionnaire assessing physical and mental health-related quality of life. Used in clinical trials and population health assessments. Suitable for pharmacoeconomic analysis, benefiting healthcare rationing.
• EQ-5D a simple quality of life questionnaire (https://euroqol.org).
• AQoL-8D a comprehensive questionnaire ^[5][6] that assesses HR-QoL over 8 domains – independent living, happiness, mental health, coping, relationships, self-worth, pain, senses (https://www.aqol.com.au).

Utility

A variety of validated surveys exist for healthcare providers to use for measuring a patient’s health-related quality of life. The results are then used to help determine treatment options for the patient based on past results from other patients,^[22] and to measure intra-individual improvements in QoL pre- and post-treatment.

When it is used as a longitudinal study device that surveys patients before, during, and after treatment, it can help health care providers determine which treatment plan is the best option, thereby improving healthcare through an evolutionary process.

Importance

There is a growing field of research concerned with developing, evaluating, and applying quality of life measures within health related research (e.g. within randomized controlled studies), especially in relation to Health Services Research. Well-executed health-related quality of life research informs those tasked with health rationing or anyone involved in the decision-making process of agencies such as the Food and Drug Administration, European Medicines Agency^[23] or National Institute for Clinical Excellence.^[24] Additionally, health-related quality of life research may be used as the final step in clinical trials of experimental therapies.

The understanding of Quality of Life is recognized as an increasingly important healthcare topic because the relationship between cost and value raises complex problems, often with high emotional attachment because of the potential impact on human life. For instance, healthcare providers must refer to cost-benefit analysis to make economic decisions about access to expensive drugs that may prolong life by a short amount of time and/or provide a minimal increase to quality of life. Additionally, these treatment drugs must be weighed against the cost of alternative treatments or preventative medicine. In the case of chronic and/or terminal illness where no effective cure is available, an emphasis is placed on improving health-related quality of life through interventions such as symptom management,^[25] adaptive technology, and palliative care.

In the realm of elder care, research indicates that improvements in quality of life ratings may also improve resident outcomes, which can lead to substantial cost savings over time. Research has also shown that quality of life ratings can be successfully used as a key-performance metric when designing and implementing organizational change initiatives in nursing homes.^[26]

Research

Research revolving around Health Related Quality of Life is extremely important because of the implications that it can have on current and future treatments and health protocols. Thereby, validated health-related quality of life questionnaires can become an integral part of clinical trials in determining the trial drugs’ value in a cost-benefit analysis. For example, the Center for Disease Control and Prevention (CDC) is using their health-related quality of life survey, Healthy Day Measure, as part of research to identify health disparities, track population trends, and build broad coalitions around a measure of population health. This information can then be used by multiple levels of government or other officials to “increase quality and years of life” and to “eliminate health disparaties” for equal opportunity. ^[27]

Ethics

The quality of life ethic refers to an ethical principle that uses assessments of the quality of life that a person could potentially experience as a foundation for making decisions about the continuation or termination of life. It is often used in contrast to or in opposition to the sanctity of life ethic.