Some of these disorders are chronic conditions with neurological causes, while others are transient and due to environmental and social factors. Shift work, pregnancy, medication and mental health problems can all cause circadian rhythm disorders.
Irregular sleep/wake disorder (ISWD) where a person sleeps at least three times per 24-hour period. This disorder can have significant impact on work and relationships. It is often linked to brain trauma, developmental disorders such as Autism, and dementia.
Advanced sleep phase disorder where a person falls asleep very early in the evening, between 6pm and 8pm, then wakes up very early 6 – 8 hours later at 2am – 5am. This is most common in elderly people.
This disorder is less problematic than others, as it still allows for the maintenance of a regular 9 – 5 work day. Increasing light exposure in the evenings can be helpful.
Delayed sleep phase disorder (DSPD) where a person cannot fall asleep until very late at night, resulting in oversleeping or extreme fatigue in the morning. Some people are fortunate enough to outgrow this condition in adolescence, when it is more common amongst boys. For approximately 0.15% of adults, the condition is lifelong and affects men and women in equal numbers.
The most viable solution for people suffering from this condition is to stay on their body’s natural sleep/wake cycle, even if that means keeping unsociable hours. Avoiding bright lights in the evenings, including computer screens, can be helpful. The disorder can impact on employment and relationships, but so too can the mental, emotional and physical deterioration that results from chronic sleep deprivation. DSPD is often misdiagnosed as insomnia or ADHD.
Some people are more sensitive to the effects of shift work than others; those who are badly affected may need to reconsider their work schedule for the sake of their health. Supplemental melatonin can be helpful for shift work disorder. Further information is provided in the shift work section of this book.
• The term “circadian” comes from Latin, and means “around a day”
• The study of circadian rhythms is known as chronobiology
• The primary characteristic of a circadian rhythm disorder is a disruption of sleep patterns, which may be on-going or temporary
• Circadian rhythms have a genetic component, with researchers noting genes in mice, fruit flies and humans that influence circadian rhythms