Influence of night shift work on psychologic state and cardiovascular and neuroendocrine responses in healthy nurses

Night shift work has often been associated with increasing degree and frequ ency of various psychologic complaints. The study examined whether psycholo gic states after night work are related to adaptive alterations of the card iovascular and neuroendocrine systems. We studied 18 healthy nurses (age 29 +/-2 years) engaged in a modified rapid shift rotation system (day work, 8: 15-17:15; evening work, 16:00-22:00; night work, 21:30-8:30). Blood pressur e, heart rate, RR interval variability (LIH and HF power spectrum for sympa thetic and vagal activities), and physical activity were measured using a m ultibiomedical recorder for 24 h from the start of work during the night an d day shifts. Plasma ACTH and cortisol concentrations were measured at the end of each shift and at 8:30 AM on a day of rest. Each subject's psycholog ic state was assessed using a validated questionnaire. Among the parameters measured, scores for confusion, depression, anger-hostility, fatigue and t ension-anxiety were highest, and scores for vigor lowest, after a night shi ft, Systolic blood pressure and heart rate during work were tower during ni ght shift than during day shift (119+/-2 vs. 123+/-1 mmHg, p<0.05 and 75+/- 1 vs. 84+/-2 bpm, p<0.001, respectively). Both parameters were lower still (p<0.005 and p<0.05) when measured outside of the hospital under waking con ditions following a night shift than following a day shift, even though the levels of physical activity were similar. The HF power spectrum of RR inte rval variability was greater not only during work (24.2+/-2.1 vs. 18.5+/-1. 8 ms, p<0.005) but also during the awake period(29.1+/-2.5 vs. 24.4+/-2.6 m s, p<0.005) after the night shift compared with the day shift. Plasma ACTH and cortisol concentrations were tower after night work than in the day of rest(7.3+/-1.2 vs. 11.5+/-2.3 pg/ml, p<0.1 and 11.1+/-1.1 vs. 14.4+/-1.1 mg /dl, p<0.05), Systolic and diastolic blood pressures during night shift wor k and the subsequent awake period correlated positively with scores for vig or and negatively with scores for confusion(p<0.05). Plasma ACTH and cortis ol concentrations did not correlate with any psychologic scores. We conclud e that psychologic disturbances after night work were associated with alter ed cardiovascular and endocrine responses in healthy nurses. Some of the ps ychologic complaints may be attributable to lower waking blood pressure.