Biological Rhythms

Diminished performance is not the only problem caused by being out of phase with one's environment. Worker and public safety also can be compromised. Researchers have found that the neural processes controlling alertness and sleep produce an increased sleep tendency and diminished capacity to function during certain early morning hours (circa 2-7 A.M.) and, to a lesser degree, during a period in the mid-afternoon (circa 2-5 P.M.), whether or not one has slept. Several studies of single-vehicle car accidents that have been judged to be fatigue-related have shown two peak times for accidents—a major one between midnight and 7 A.M., and a secondary peak between 1 and 4 P.M.

Shift work is a necessity in an industrially developed country. Manufacturing, transportation, and health care rely on shift workers to maintain operations around the clock. A shift worker can be defined as someone who works evenings, nights, rotating shifts, or extended shifts. Unlike jet lag, which is usually a temporary disruption, shift work schedules and their disruptions can last for years. Humans are diurnal creatures (active during the day), and shift workers are often out of sync with environmental and social cues. Circadian adjustment to a new shift is gradual (taking a week or more), and changing to a new shift before adjustment is complete can cause perpetual desynchronization. Research shows that shift workers suffer from sleep disruption and fatigue, domestic disturbances, and health problems such as gastrointestinal disorders and increased risk of cardiovascular disease. Task performance is also poorer at night. In order to minimize circadian disruptions, many large companies employ consulting firms to advise them on how to manage or prevent problems caused by shift work. Other than adjusting schedules, implementing educational and support programs regarding biological rhythms, sleep, and family counseling may be a good way to improve the coping ability of shift workers.

Compromised performance among health care workers can jeopardize patients' lives. The medical profession is notorious for having its doctors-in-training work very long hours. In the case of a young woman who died eight hours after being admitted to the emergency room, the intern and resident had each been on duty for 18 hours before treating her. The grand jury examining the case determined that the number of hours the residents and interns were required to work contributed to her death. Some improvements may be on the way in the medical profession as well. The Accreditation Council for Graduate Medical Education (ACGME), which sets standards for medical residency training programs, has begun within the past few years to introduce new standards for residents' work hours.