| The key factors that influence fatigue include accumulated hours without sleep and changes in circadian rhythm. |
| As a consequence, most biological processes, from sleep-wake cycles in people to leaf movements in plants, follow a daily, circadian rhythm. |
| In human adults, many biological functions display a physiological circadian rhythm that oscillates in synchronism with the sleep-wake rhythm. |
| Chapter 6 deals with circadian rhythm and chronotherapy of asthma medications. |
| However, the accident took place during a time of day when a person's circadian rhythm is known to be at a low point. |
| During their first few days, newborns sleep for very short periods of 3-4 hours on average, without any circadian rhythm. |
