To examine the effect of night shift on the ovarian function, 122 teachers, 67 office workers, 377 nurses, 133 factory workers and 67 barmaids were surveyed. The incidence of irregular menstrual cycle was 13.1% in teachers, 14.9% in office workers, 24.9% in nurses, 36.8% in factory workers and 40.3% in barmaids. The incidence was significantly higher in women working at night than women working during the day. Plasma concentrations of melatonin, LH, FSH and prolactin were determined at 2200 h and 0200 h in 5 nurses working at night and in 6 nurses resting in their quarters. Plasma concentrations of melatonin and prolactin at 0200 h were significantly lower in nurses of the working group than others of the resting group, but plasma concentrations of LH and FSH did not differ between the two groups. These results indicate that night shift suppresses the ovarian function by affecting the circadian rhythm of melatonin and prolactin.

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To determine the risk factors of the subjective symptoms experienced by chain saw workers, we surveyed 206 forestry workers using this device in their work. The strength of the relationship between their symptoms and such potential risk factors as occupational, behavioral, and physical factors was evaluated by a multiple logistic regression model. It was found that many years of chain saw operation, and numerous hours of chain saw operation per day, increased the risk of white finger, numbness of hands and arms, chilliness of hands and arms and difficulty in joint movement, indicating that these symptoms were closely related to vibration exposure. Many years of forestry work before chain saw work also increased the risk of joint pain, suggesting that bone and joint disorders are related to heavy manual work not using a chain saw. A second job involving manual labor increased the risk of weakness in the arms, stiffness of the shoulders, and lumbago. Infrequent bathing was associated with increased risk of pain in hands and arms and lumbago. Older workers had a higher prevalence of stomach discomfort. No risk factor was found to significantly increase the risk of easy fatigability, forgetfulness and sleep disorder. It was found that not only exposure to vibration but also other factors contributed to the prevalence of pain in hands and arms, joint pain, weakness in arms, stiffness of shoulder, and lumbago. Second job and infrequent bathing appeared to be related to the occurrence of certain subjective symptoms. These contributory factors should be taken into account when evaluating subjective symptoms encountered in field studies of forestry workers.

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To assess the validity of a new simplified cold water immersion test (4°C-1 min method) for peripheral circulatory function, comparison was made with the conventional method (10°C-10 min method). These two different methods of cold immersion test were applied to 23 patients with vibration disease and 24 healthy men. Observation was made on finger skin temperature by a thermistor and complaints in the hand by a 5-step self-reported scale method every minute during the test. The patterns of recovery of skin temperature after cold immersion in each group were similar in both methods. Pain in the hand in the 4°C-1 min method was less than that in the 10°C-10 min method. The recovery rate at 5 min in the patients with Raynaud's phenomenon was lower than that in those without Raynaud's phenomenon in the 4°C-1 min method (p<0.01). However, no significant differences were noted in 10°C-10 min method. The results suggest that the new method is feasible in detecting the response of vasodilation after immersion. In the recovery rate at 5 min after immersion, near values of the sensitivity and specificity were observed between 50% cut-off values in the 4°C-1 min method and 30% value in the 10°C-10 min method. Thus, the 4°C-1 min method is considered to be more useful to evaluate the physiological response after cold immersion than the 10°C-10 min method.

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The changes in mental workload and fatigue during a one-day transcribing task were examined by determining some subjective and physiological measures which reflect mental activity. With an interval of one week between the three test days, 12 male students rested and performed self-paced transcribing task with moderate and maximum effort for 8 h each.
The subjects transcribed more characters in the task with maximum effort than with moderate effort. In both the morning and afternoon, adrenaline excretion increased and heart rate decreased with the lapse of time. In linear proportion to the total working hours, occipital midline beta-2 amplitude, subjective rating of tiredness and subjective symptoms of fatigue rose, but critical flicker values fell slightly in the task with maximum effort. It was inferred from these results that with lapse of working hours intellectual activity and feeling of fatigue increase and the level of arousal slightly declines. Hence, it was considered that mental workload becomes heavier and subjective feeling of fatigue increases as the working hours become longer.

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