Resynchronization of blood pressure circadian rhythm after westward trans-7-meridian flight with and without melatonin treatment.

Blood pressure (BP) of a healthy 37-yr-old male traveling from Milan to Houston was monitored for 36 h before the flight and continued for 5 d after the arrival. The rhythmometric analysis of BP data was made to investigate the rate of adaptation to a rapid rest-activity cycle shift. Since two trips were evaluated, during the second one the subject took melatonin (3 mg) before the nocturnal rest. In the first trip the BP circadian rhythm synchronization occurred on the 5th day. In the second trip melatonin promoted an immediate but unstable adaptation to the new rest-activity cycle.