A general index of self-reported sleep: the sleep quotient

Utilizing multiple sleep measures, a practice common to virtually all sleep assessments, poses problems both for statistical analyses in the form of inflated Type I error rate and for interpretation by the inability to specify general sleep change. A sleep quotient (SQ) is proposed that appears to overcome these problems. The paper presents archival norms for self-report sleep data, demonstrates the use of these norms in transforming novel data to standardized units, and casts the standardized score in the form of an intelligence quotient, now called a SQ, with a mean of 100 and a standard deviation of 15. Previously published data are reanalyzed by use of SQ scores, methods of interpreting SQ data are demonstrated, and advantages of SQ analyses are described. The SQ appears to be a valid, useful composite sleep index permitting the measurement of general sleep. (C) 1997 Elsevier Science Ltd.