[Chrono-type as a factor of shiftwork tolerance in women]

Almost all physiological and psychological functions of human beings reveal circadian variations. The parameters of those rhythms differ in various subjects dependently on their individual diurnal characteristics, named here chrono-type. The difference in phase of maximal arousal is particularly apparent so that it implies the distinction between the morning and the evening types. The comparative study of both chrono-types was done with regard to the subjective health, sleep disorders and disturbances, attitudes towards shiftwork and physical fitness as measured by indirect prediction of the maximal oxygen uptake. In spite of differences in the bedtime and awaking time, representatives of morning and evening type did not differ when considering the amount of sleep. Both groups slept about one hour less than subjectively required. The analysis of sleep disorders (during days with various shifts and days off) showed that their configuration was different in compared groups. Morning types more often woke before proper time and suffered from frequent mid-sleep awakenings. They had also more difficulties in falling asleep and felt tired after awakening when working night shift. Evening types reported more often difficulties in awakening (independently on work shift) and complained low well-being or tiredness after awakening when working morning or afternoon shift and during days off. The percentage of morning types reporting various sleep disturbances of external (noise, daylight) or internal (hunger, nervousness) origin was 13 to 74. The corresponding figures for evening types were 4 to 52%. Subjective health was assessed with use of a list of 74 symptoms. It was found that morning individuals significantly more frequently reported fevers and sub-febrile states, itching in heart region, pains or tightness in heart region when nervous and musculoskeletal pains. No significant differences in gastrointestinal complaints were found. Analysis of typical circulatory, respiratory and musculoskeletal syndromes revealed the lower frequency of circulatory and musculoskeletal complaints and more respiratory symptoms in evening types. This latter could be considered as the result of prevalence of smokers in this group. The prediction of maximal oxygen uptake with use of indirect Astrand-Rhythm method showed significantly higher values in evening types. Taking into account that the result of this method is based on the heart rate response to submaximal load--it is highly probable that the difference observed is due to chrono-type related difference in phase of circadian rhythm of heart rate reaction to the load applied on the same time of the day. Both studied groups differed significantly as to the percentage of persons approving the work in shifts.(ABSTRACT TRUNCATED AT 400 WORDS)