Circadian rhythms in human performance and mood under constant conditions

This study explored the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, subjective alertness and well‐being. Seventeen healthy young adults were studied under 36 h of «unmasking» conditions (constant wakeful bedrest, temporal isolation, homogenized «meals») during which rectal temperatures were measured every minute, and plasma cortisol and plasma melatonin measured every 20 min. Hourly subjective ratings of global vigour (alertness) and affect (well‐being) were obtained followed by one of two performance batteries. On odd‐numbered hours performance (speed and accuracy) of serial search, verbal reasoning and manual dexterity tasks was assessed. On even‐numbered hours, performance (% hits, response speed) was measured at a 25–30 min visual vigilance task. Performance of all tasks (except search accuracy) showed a significant time of day variation usually with a nocturnal trough close to the trough in rectal temperature. Performance rhythms appeared not to reliably differ with working memory load. Within subjects, predominantly positive correlations emerged between good performance and higher temperatures and better subjective alertness; predominantly negative correlations between good performance and higher plasma levels of cortisol and melatonin. Temperature and cortisol rhythms correlated with slightly more performance measures (5/7) than did melatonin rhythms (4/7). Global vigour correlated about as well with performance (5/7) as did temperature, and considerably better than global affect (1/7). In conclusion: (1) between‐task heterogeneity in circadian performance rhythms appeared to be absent when the sleep/wake cycle was suspended; (2) temperature (positively), cortisol and melatonin (negatively) appeared equally good as circadian correlates of performance, and (3) subjective alertness correlated with performance rhythms as well as (but not better than) body temperature, suggesting that performance rhythms were not directly mediated by rhythms in subjective alertness.

[1]  M. J. Blake,et al.  Time of day effects on performance in a range of tasks , 1967 .

[2]  G. Siegmund.  [Sleep and wakefulness]. , 1972, Krankenpflege.

[3]  A Fort,et al.  Psychometric performance: circadian rhythms and effect of raising body temperature. , 1973, The Journal of physiology.

[4]  Timothy H. Monk,et al.  Circadian aspects of subjective sleepiness: A behavioural messenger? , 1991 .

[5]  R T Wilkinson,et al.  Methods for research on sleep deprivation and sleep function. , 1970, International psychiatry clinics.

[6]  A. Borbély.  A two process model of sleep regulation. , 1982, Human neurobiology.

[7]  N. Mackworth.  The Breakdown of Vigilance during Prolonged Visual Search 1 , 1948 .

[8]  P Pátkai,et al.  Interindividual differences in diurnal variations in alertness, performance, and adrenaline excretion. , 1971, Acta physiologica Scandinavica.

[9]  T. Åkerstedt,et al.  The circadian covariation of fatigue and urinary melatonin. , 1982, Biological psychiatry.

[10]  S Folkard,et al.  Diurnal variation in logical reasoning. , 1975, British journal of psychology.

[11]  Daniel J Buysse,et al.  Patterns of sleep episodes in young and elderly adults during a 36-hour constant routine. , 1993, Sleep.

[12]  Timothy H. Monk,et al.  Time of day effects in simple repetitive tasks: Some possible mechanisms , 1982 .

[13]  C A Czeisler,et al.  Short‐term memory, alertness and performance: a reappraisal of their relationship to body temperature , 1992, Journal of sleep research.

[14]  P Lavie,et al.  The search for cycles in mental performance from Lombarb to Kleitman. , 1980, Chronobiologia.

[15]  Timothy H. Monk,et al.  Circadian rhythms in human memory , 1980 .

[16]  T. Monk,et al.  «Cosina»: a cosine curve fitting program mitable for small computers , 1983 .

[17]  J. Fröberg.  Twenty-four-hour patterns in human performance, subjective and physiological variables and differences between morning and evening active subjects , 1977, Biological Psychology.

[18]  W. P. Colquhoun,et al.  Biological Rhythms and Human Performance , 1971 .

[19]  T. Monk.  Sleep, sleepiness, and performance , 1991 .

[20]  T. Monk,et al.  The Measurement of Circadian Rhythms in Psychological Functions , 1987 .

[21]  A. Craig,et al.  Diurnal variation in vigilance efficiency. , 1981, Ergonomics.

[22]  D. Laird,et al.  Relative performance of college students as conditioned by time of day and day of week. , 1925 .

[23]  N. Kleitman,et al.  Body temperature and performance under different routines. , 1950, Journal of applied physiology.

[24]  Timothy H. Monk,et al.  A visual analogue scale technique to measure global vigor and affect , 1989, Psychiatry Research.

[25]  D. Dijk,et al.  Circadian and sleep/wake dependent aspects of subjective alertness and cognitive performance , 1992, Journal of sleep research.