A new and "non-invasive" technique to identify a person's natural sleep pattern has been developed, university researchers have said.

Researchers from the School of Medicine at Swansea University tested the method at Cheltenham Science Festival to identify their natural pattern of wake and sleep - known as the circadian rhythm.

All that is required from the subject is a quick cheek-swab. Previously, blood samples were required to obtain the ribonucleic acid (RNA) needed for this type of research, the university said.

Identifying the circadian rhythm can reveal whether someone is "an early bird" or "night owl", scientists said.

Sarah Forbes-Robertson, research fellow at the Swansea School of Medicine, said: "Previously you needed to take blood samples to obtain the RNA needed for this type of research. Our technique allows us to get a usable sample just by swabbing the inside of an individual's cheek."

A number of different genes control an individual's natural circadian rhythm. The levels of RNA produced by these different genes indicate how active they are at different times of day.

One gene known as Per2 produces the highest levels of RNA at around 4am, and is the gene associated with sleep, researchers said.

The gene examined at Cheltenham Science Festival, which produces its highest levels at 4pm, known as REV-ERB, works in opposition to Per2 and is thought by researchers at Swansea to be associated with wakefulness.

Dr Forbes-Robertson said if a person produces higher levels of REV-ERB before 4pm, they are likely to be "an early bird". If someone produces higher levels after 4pm, they are likely to be a "night owl".

Researchers at Swansea University plan to use the technique to look at various conditions such as Attention Deficit Hyperactivity Disorder (ADHD) to see if they are linked to disturbed circadian rhythms.