The urinary 6-sulfatoxymelatonin level after three different work schedules with 2, 4 and 7 consecutive night shifts among Danish police officers.

Night shift work suppresses excretion of melatonin, but little is known about the needed time for recovery. We aimed to compare levels of 6-sulfatoxy melatonin after three different night shift schedules, including recovery days. In a quasi-experimental, within-subject crossover study, 73 male police officers in Denmark collected morning urine after the last recovery day in three different work schedules with two, four, and seven consecutive night shifts followed by a corresponding number of days for recovery. We found no significant differences for 6-sulphatoxymelatonin concentrations in morning urine between the three different work schedules indicating similar recovery of melatonin suppression in the studied work schedules.