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Twelve subjects were kept awake for 64 h under conditions of isolation from external time cues. Activity was sedentary and kept as constant as possible over time, as was intake of food and drink. Cardiovascular variables — blood pressure, heart rate, contractility (IJ-amplitude from ballistocardiogram), T-wave amplitude, QRS, PQ and QT intervals — were assessed every 3 h. At the same intervals, urine samples for catecholamine analysis were obtained. Data were analyzed by analysis of variance and cosinor techniques. Adrenaline excretion showed a pronounced circadian rhythm. Noradrenaline excretion and IJ amplitude showed much weaker rhythmicity, statistically significant only with the cosinor technique. The remaining variables showed no rhythmicity with either technique. It was concluded that constant conditions (including sleep deprivation) markedly disturb or even obliterate the circadian rhythms of cardiovascular variables and urinary noradrenaline excretion. It was also concluded that most of the amplitude of cardiovascular circadian rhythms measured under habitual sleep/wake conditions must be due to the alternation between sleeping and waking. The present data do not, however, rule out the existence of selfsustained circadian rhythmicity in cardiovascular variables; a design including continuous wakefulness may well have concealed endogenous low-amplitude rhythms.

The present study sought to relate the well-being of night workers to that of the working population in general. One hundred and ninety-seven male permanent night security guards were interviewed with regard to the occurrence of various symptoms during the previous 12-month period. The results were compared with the results from similar interviews with a representative national sample of males (n= 1769) in the Swedish workforce. An age standardized morbidity ratio was computed with control for various background variables. The results showed that the security guards had a 2-3 times higher occurrence of sleep disturbances and fatigue than the national sample. Among the variables notdiffering from the national sample were gastrointestinal problems, headache, nervous problems, depression, nausea, diarrhoea, and haemorrhoids. It was concluded that sleep/wake disturbances are considerably more usual in permanent night security guards than in the working population as a whole.

The diurnal variation in body temperature, catecholamine excretion, performance, and subjective alertness was studied among 24 permanent night workers during the 1st, 3rd, and 5th day of their work ' week 'of six nights. Most of the variables showed a significant diurnal pattern with high values during work. Furthermore, the patterns of variation were similar during the three nights of measurement without any observable adjustment over the week. It was therefore suggested that permanent night work might facilitate a more rapid switch over to night work after free days.

Established nutritional science methods and a new concept for meal-classification were applied to shiftworker (rotating 3-shift) data. The frequency of meals and snacks of different nutritional quality as a function of work schedule was evaluated, as well as the content of selected nutrients (energy, fat, sucrose, dietary fibres, ascorbic acid) in these meals and snacks. The results do not indicate that rotating 3-shift work affects the nutritional quality of the diet or the frequency of different types of meals and snacks. A qualitative classification of meals and snacks might be a cost-effective strategy for data-evaluation in field studies of shift workers' eating habits when quantitative estimations of the dietary intake are to be complicated.

Twelve subjects were kept awake for 64 h under conditions of isolation from external time cues. Activity was sedentary and kept as constant as possible over time, as was intake of food and drink. Cardiovascular variables — blood pressure, heart rate, contractility (IJ-amplitude from ballistocardiogram), T-wave amplitude, QRS, PQand QTintervals — were assessed every 3 h. At the same intervals, urine samples for catecholamine analysis were obtained. Data were analyzed by analysis of variance and cosinor techniques. Adrenaline excretion showed a pronounced circadian rhythm. Noradrenaline excretion and IJ amplitude showed much weaker rhythmicity, statistically significant only with the cosinor technique. The remaining variables showed no rhythmicity with either technique. It was concluded that constant conditions (including sleep deprivation) markedly disturb or even obliterate the circadian rhythms of cardiovascular variables and urinary noradrenaline excretion. It was also concluded that most of the amplitude of cardiovascular circadian rhythms measured under habitual sleep/wake conditions must be due to the alternation between sleeping and waking. The present data do not, however, rule out the existence of selfsustained circadian rhythmicity in cardiovascular variables; a design including continuous wakefulness may well have concealed endogenous low-amplitude rhythms.