Police officers' responses to 8 and 12 hour shift schedules

The opportunity arose to conduct an extensive before and after study when a city police force changed from an 8 hour 12 day shift cycle to a 12 hour 8 day system. W170, blood pressure, sleep duration, sleep quality and subjective level of alertness measures showed improvements with the new system. Critical flicker fusion showed reliable within shifts decrements, but no between system differences. Oral temperature showed the expected circadian changes with no indication of phase shift under either system. Urinary catecholamine and grammatical reasoning measures showed no influence of shift-related factors. The overwhelming atmosphere of support for the new system coupled with the absence of any negative ergonomics evidence led to its adoption on a permanent basis.