Circadian rhythm sleep-wake disorders are common. Jet lag is an easily recognisable example that many people have experienced. The main cause of these conditions is a mismatch between the body’s inbuilt biological rhythm for sleepiness (“circadian rhythm” or body clock) and the day to day sleep wake needs of the individual. For example, with jet lag, after arriving in a new time zone, your body clock may still be set to a night time sleep period even though it is daytime in your destination. You will then tend to fall asleep during the day in your new destination until your body clock adapts to the new time zone.
Other examples of circadian rhythm sleep-wake disorders are:
Advanced sleep phase disorder - common in the elderly and associated with evening sleepiness and early morning insomnia
Delayed sleep phase disorder - common in adolescents and may progress to adulthood. Sufferers find it hard to fall asleep before 2-3 am. If they need to wake up at around 7-8 am to attend school, work etc they may be very tired during the day. If left alone, individuals with a delayed sleep phase disorder would habitually sleep until around midday. This condition can be very disruptive to school, work, study and family life.
Shift work sleep disorder – all shift workers have some problems adjusting to shift changes, but in some cases, their problems are severe with the body clock not adapting. These sufferers may perform poorly at work, have accidents due to sleepiness or even stop shift work because of their severe symptoms. This condition can be treated with medications if properly diagnosed.