Professor Colin Espie, Director of the University of Glasgow Sleep Centre and co-founder of Sleepio, will be online at 3pm on Thursday 27 January to answer your questions.

Professor Espie's research interests include the pathophysiology of insomnia, primary and secondary sleep disturbance (particularly sleep and depression, and sleep and cancer), and cognitive behavioural therapy (CBT) for insomnia.

Post your questions on sleep issues below.

Don't miss the Guardian on Saturday 29 January for your free 'Good sleep handbook', and the Observer on Sunday 30 January for a free sleep relaxtion CD.