8.6 The Impact of Shift Work on Circadian Rhythms

Individuals working evening or night shifts are exposed to different amounts of light in different patterns than those who work only during daytime hours—similar to when individuals who live at extreme latitudes are exposed to sunlight for extended periods each day. Not surprisingly, shift work can lead to significant changes in circadian rhythms. In addition to those who work night shifts, many work schedules can affect circadian rhythms, such as early start times, overtime, on-call status, or inconsistent schedules. Those who work shifts that require more nighttime wakefulness and daytime rest must take extra steps to ensure quality sleep. The following tips can help:

• During night shift work, individuals can seek out exposure to bright lights and opportunities for physical activity to maintain alertness.
• Shift workers should consider limiting caffeine consumption to the first half of the shift or at least four hours before they plan to go to sleep.
• Taking a nap before the beginning of a shift can improve alertness (Schweitzer et al., 2006) and taking a nap mid-shift—when possible—can lead to increased alertness and improved reaction time during the second half of a shift (Sallinen et al., 1998). Even a 20-minute nap has been shown to improve performance and alertness during shift work (Purnell et al., 2002).
• Whenever possible, prioritize adequate amounts of quality sleep during non-working hours.
• Prevent or reduce sleep disturbances like sound and light distractions by using white noise or blackout curtains.

While not for everyone, shift work is only a problem if it’s leading to inadequate sleep or excessive fatigue during waking hours.