Using nine 2-h delays to achieve a 6-h advance disrupts sleep, alertness, and circadian rhythm.

UNLABELLED: A ground-based study was undertaken to determine whether circadian and sleep dysfunction could be avoided by "trickling in" a 6-h phase advance in sleep/wake schedule by nine consecutive 2-h phase delays, as would be recommended by NASA's Appendix K guidelines. METHODS: A 16-d (384-h) mission was simulated in 10 subjects (5 men, 5 women, mean age: 41.2 yr), studied singly or in pairs. After 14 d on a 23:00-07:00 sleep/wake cycle, the subject entered the laboratory. After a 4-d baseline segment, repeated 2-h phase delays were then required on each of the next nine successive nights of the study (i.e., bedtimes at 01:00, 03:00, 05:00, etc.), resulting in an eventual movement of bedtimes to an 18-h phase delayed (equivalent to a 6-h phase advanced) position with bedtime at 17:00. Measures taken throughout the laboratory study included polysomnographically measured sleep, circadian rhythms in rectal temperature, and subjective ratings of mood and alertness. RESULTS: Circadian dysfunction and sleep disruption were not avoided by trickling in the phase shift. The circadian pacemaker appeared to delay its phase by an average of about 1 h later per night, rather than the 2 h later per night required by the imposed routine. This resulted in a progressive decrease in circadian temperature rhythm amplitude, a progressive disruption in sleep, and a progressive lowering in subjective ratings of alertness. CONCLUSION: Doubt must be cast on the assertion that circadian dysfunction and sleep loss can be avoided by limiting repeated phase delays in routine to 2 h.

Morningness-eveningness and lifestyle regularity.

The relation between morningness (M) - eveningness (E) and lifestyle regularity was studied in a convenience sample of 100 healthy subjects aged between 20 and 59 yrs (47 males and 53 females; mean age 33.6 yrs). Morningness-eveningness was measured by a single administration of the 13-item Composite Scale for Morningness (CSM). Lifestyle regularity was measured by requiring subjects to complete a five-item Social Rhythm Metric diary (SRM-5) each evening for two weeks. Each week of SRM-5 was analyzed separately and the two SRM scores averaged to yield the lifestyle regularity measure for the subject. Subjects were categorized by morningness into top and bottom quartiles of CSM score (denoted M-types and E-types, respectively), with the remaining 50% of subjects denoted as intermediate (I-types). Mean SRM scores significantly differed between the three morningness groups (p <0.001) in the order E-types (SRM = 3.6), then I-types (SRM=4.0), then M-types (SRM=4.9), with higher scores indicating greater daily lifestyle regularity. The effect size of the E-type versus M-type difference was approximately 1.3. The relationship between the CSM and SRM scores was also confirmed using a correlational analysis (rho = 0.428; p < 0.001). This correlational finding was substantially weaker when age was partialed out (r=0.186; p=0.065), although there was still a trend toward a significan relationship. Thus it appears that morning types appear to be more regular in their daily lifestyle than are evening types, suggesting a relationship between these two aspects of human circadian behavior.

Measuring sleep habits without using a diary: the sleep timing questionnaire.

STUDY OBJECTIVES: To develop a single-administration instrument yielding equivalent measures of sleep to those obtained from a formal (2-week) sleep diary. DESIGN & SETTING: A single-administration Sleep riming Questionnaire (STQ) is described (and reproduced in the Appendix). Test-retest reliability was examined in 40 subjects who were given the STQ on two occasions separated by less than 1 year. Convergent validity was measured both by comparing STO-derived measures with objective measures derived from wrist actigraphy (n=23) and by comparing STQ-derived measures with other subjective measures derived from a detailed 2-week sleep diary in two nonoverlapping samples (n=101, 93). Correlations of STQ measures with age and momingness-eveningness (chronotype) were also examined. SUBJECTS: The analyses used sample sizes of 40, 23, 101, and 93 (both genders, overall age range 20y-89y). Most subjects were healthy volunteers; some Study 4 subjects were patients (enrolled in research protocols). RESULTS: Test-retest reliability for the STQ was demonstrated for estimates of bedtime (r = 0.705, p < 0.001) and waketime (r = 0.826, p < 0.001). Convergent validity using wrist actigraphy was demonstrated by correlations of 0.592 (p < 0.005) for bedtime, and of 0.769 (p < 0.001) for waketime. Diary studies indicated STQ bedtime and waketime data to be highly correlated (at about 0.8) with those obtained from a formal 2-week sleep diary. The STQ also provided data on estimated sleep latency and wake after sleep onset (WASO), which correlated reliably (at about 0.7) with average nightly ratings of these variables from a 2-week sleep diary. Mean estimated values of sleep latency and WASO from the two instruments were within 1 minute of each other. ST-derived bedtimes and waketimes correlated with both age and chronotype in the expected direction (older subjects earlier, morning types earlier). CONCLUSION: The STQ may be a reliable valid measure of sleep timing that could provide a time-efficient alternative to traditional sleep diaries.

The relationship between lifestyle regularity and subjective sleep quality.

In previous work we have developed a diary instrument-the Social Rhythm Metric (SRM), which allows the assessment of lifestyle regularity-and a questionnaire instrument--the Pittsburgh Sleep Quality Index (PSQI), which allows the assessment of subjective sleep quality. The aim of the present study was to explore the relationship between lifestyle regularity and subjective sleep quality. Lifestyle regularity was assessed by both standard (SRM-17) and shortened (SRM-5) metrics; subjective sleep quality was assessed by the PSQI. We hypothesized that high lifestyle regularity would be conducive to better sleep. Both instruments were given to a sample of 100 healthy subjects who were studied as part of a variety of different experiments spanning a 9-yr time frame. Ages ranged from 19 to 49 yr (mean age: 31.2 yr, s.d.: 7.8 yr); there were 48 women and 52 men. SRM scores were derived from a two-week diary. The hypothesis was confirmed. There was a significant (rho = -0.4, p < 0.001) correlation between SRM (both metrics) and PSQI, indicating that subjects with higher levels of lifestyle regularity reported fewer sleep problems. This relationship was also supported by a categorical analysis, where the proportion of "poor sleepers" was doubled in the "irregular types" group as compared with the "non-irregular types" group. Thus, there appears to be an association between lifestyle regularity and good sleep, though the direction of causality remains to be tested.