183 Assessment of quality of life in sleep apnea

Abstract

An important goal of the management of patients with sleep apnea is to alleviate symptoms and dysfunction attributable to the disease. Because symptoms are usually poorly correlated with physiological indices measured in laboratory, quality of life should be assessed directly. The concept of ‘‘quality of life’’ usually refers to the patients’ perception of performance in at least one of four important domains: (1) somatic sensation; (2) physical function, (3) emotional state, and (4) social interaction. The term ‘‘health-related quality of life’’ is often used when widely valued aspects of life not directly related to health, such as income and freedom, are not considered. In clinical studies, the selection of quality-of-life questionnaires must be guided by the investigators’ objectives. Discriminative questionnaires distinguish between groups of patients and are most often used to describe study populations. Discriminative questionnaires must have validity (which refers to whether the instrument is measuring what it claims to measure) and reliability (the ability of the instrument to consistently discriminate between more and less affected patients). Evaluative questionnaires measure change over time. Responsiveness (i.e., the ability of an evaluative instrument to detect real change, even when it is small) is a necessary property for evaluative instruments. For a discriminative instrument, a score is interpretable when it tells to the reader whether the difference between two patients’ function is negligible, small, moderate, or large. For an evaluative instrument, a score is interpretable when it tells to the reader whether a particular change in score represents a small, moderate, or large clinical improvement or deterioration. Clinicians and policymakers are more and more recognizing the importance of measuring health-related quality of life to inform patient management and policy decisions. A clear understanding of the fundamentals of quality-of-life measurement is essential.