Outcome measurement in sleep medicine practice and research. Part 1: assessment of symptoms, subjective and objective daytime sleepiness, health-related quality of life and functional status

Abstract

The documentation of treatment outcomes has gained increased importance as those responsible for paying for healthcare focus on the delivery of cost-effective care. The practitioner and researcher, challenged with documenting the clinical significance of their endeavors, must depend on conceptually appropriate, valid and reliable instruments. Outcomes of particular relevance for sleep disorders include self-reported general symptoms, subjective and objective daytime sleepiness, neurobehavior, health-related quality of life (HRQL) or functional status, incidence of accidents and cardiovascular morbidity, and health care utilization and cost. This paper will limit its focus to the outcomes of self-reported general symptoms, subjective and objective daytime sleepiness, and HRQL or functional status. In addition to describing measures that could be applied to evaluate these outcomes, this paper will also discuss factors affecting the selection of outcome measures for use in research and practice, and consider evidence generated with the application of these instruments in research. Reductions in self-reported symptoms, such as snoring and daytime hypersomnolence following treatment, have been documented with the application of measures with strong psychometric properties such as the Survey Screen for Sleep Apnea and Epworth Sleepiness Scale. In addition to statistical reliability, calculation of the effect size and standardized response mean indicate that these changes are also clinically meaningful. Similar improvements have also been demonstrated using the Multiple Sleep Latency Test (MSLT), although the resulting increased latency has not typically been within normal values. Important improvements following treatment have been documented with the Maintenance of Wakefulness Test (MWT). Evidence suggests that the MWT may be more sensitive in situations, such as narcolepsy, where there are high levels of physiologic sleepiness, reserving the MSLT where the physiologic sleep tendency is more restricted, such as in obstructive sleep apnea (OSA). Patients>> perceptions of the benefit of treatment to their daily lives have been documented by such generic measures of HRQL, such as the SF-36 and Nottingham Health Profile. However, the impact of sleep disorders and the benefit of treatment on those aspects of daily behavior likely to be most affected have more clearly been demonstrated with the utilization of disease-specific HRQL measures such as the Functional Outcomes of Sleep Questionnaire and the Calgary Sleep Apnea Quality of Life Index. 2001 Harcourt Publishers Ltd