Endocrine Abstracts

Background & aim: Night shift work is associated with a disruption of circadian rhythms, where a person’s internal body clock is in conflict with the rotating shift schedule. The circadian rhythm of the human body is characterized with an alternating sleep-wake cycle. Shift work has been associated with increased risk of hypertension, cardiovascular diseases and hormonal disturbances. The Present study was aimed to investigate the effects of rotating night shift on 24 h chronomics of BP/HR and its relation with 6-sulfatoxy melatonin levels.

Material & methods: healthy nursing professionals, aged 20–40 year, performing day and night shift duties were recruited. Each study subject had a monthly scheduled of regular nine night shifts (12 h night shift, from 2000 to 0800 h) followed by remaining 17–18 day shifts (6 h day shift, from 0800 to 1400 h) with a total of 4 days off in between. Subjects were recruited from the Trauma Center, GM and Associated Hospitals, King George’s Medical University, Lucknow, UP, India. The duration and pattern of shift work were the same among all the subjects. Ambulatory BP and HR were recorded at every 30 min intervals in day time and each hour in night time synchronically with circadian pattern of 6 sulfatoxy melatonin during shift duties. 6-sulfatoxy melatonin (melatonin sulphate) was estimated by Competitive ELISA method (IBL international melatonin sulphate ELISA kit).

Results: Highly Significant difference was found in double amplitude (2DA) of blood pressure between night and day shift (P<0.001). Ecphasia (odd timing of circadian pattern of blood pressure not of heart rate) was also found in few subjects. In night shift, hyperbaric index (HBI) of mean systolic blood pressure was found to be increased at 2400–0300 h (midnight) while during day shift, peak was found at 0600–0900 h. Peak melatonin was to be found in early morning as compared to mid night in both the shift.

Conclusion: The present study concluded that the desynchronisation appeared during night shift and entrainment of circadian rhythm in the day shift.