THE USE OF SURVEY MEASURES TO ASSESS CIRCADIAN VARIATIONS IN ALERTNESS

Current models of sleep regulation postulate both a homeostatic and ci rcadian component and promise an understanding of disturbed and displa ced sleep. Estimates of these components have traditionally required r elatively cumbersome and costly measures, including sleep electroencep halograms and continuously recorded rectal temperature, but it has rec ently been demonstrated that they may successfully be based on frequen t (e.g. 2-hourly) concurrent ratings of alertness. This paper examines whether similar results might be obtained using retrospective survey measures of alertness obtained from shiftworking nurses at a single si tting. These retrospective measures are shown to be sensitive to bath time of day and shift, to have a high level of reliability even for re latively small sample sizes (e.g. 10) and to be valid predictors of mo re traditional concurrent measures of alertness. It is concluded that retrospective alertness ratings may prove to be an extremely cost-effe ctive method for examining the trends in alertness in various groups, including those suffering from specific types of sleep disorder.