There are many causes of excessive daytime sleepiness, and Obstructive Sleep Apnoea is one of the most common. Other common causes of excessive daytime sleepiness include:

• Central Sleep Apnoea Syndromes
• Psychological disorders that affect sleep, such as depression
• Neurological disorders such as narcolepsy and cataplexy
• Insomnia and parasomnias
• Periodic limb movement disorders
• Different medications
• Social factors such as shift work

As with any other disease, confirmation is necessary before embarking on potentially lifelong treatment. Accurate diagnosis of sleep disorders is  the responsibility of an experienced physician. Nevertheless, a practitioner who is involved in the diagnosis and management of a sleep patient should understand the differential diagnosis of the most common sleep disorders.