Differential diagnosis of delayed sleep phase disorder

Elise

Delayed sleep phase disorder (DSPD) can have major impact on a person’s health and wellbeing. The disorder is characterised by delayed sleep timing, relative to desired sleep timing – for example, that which would be optimal for work or school. Finding the right treatment may take time and has been made even more complex by the recent characterisation of two distinct groups within the DSPD population – one with a circadian delay, and one with typical circadian timing.

These different physiological causes between patients with DSPD mean that almost half of these patients do not actually have a circadian basis to their sleep problems (despite being diagnosed with a ‘circadian rhythm sleep disorder’), and are therefore being misclassified – and mistreated.

MICCN set out to find a way to differentiate DSPD patient groups so that a proper, timely diagnoses can be made, and the right treatment found.

“We investigated the use of the pupillary light reflex as a method of differentiating the circadian and non-circadian type DSPD patients” PhD student Ms Elise McGlashan said.

Three groups of young adults with either circadian DSPD, non-circadian DSPD or no sleep disorder diagnosis completed the study.

Investigating the pupillary light reflex in these groups gave an indication of how much light is being transmitted from the eye to the body clock in the brain. A faster pupillary light reflex may indicate ‘hypersensitivity to light’, which can lead to delayed circadian timing.

“Circadian DSPD patients showed a significantly faster pupillary light reflex than both non-circadian DSPD patients and healthy controls,“ Ms McGlashan said. “The strongest predictor could differentiate between circadian and non-circadian DSPD patients with 87% accuracy. These results support the potential for the pupillary light reflex to clinically differentiate between DSPD patients with normal vs. delayed circadian timing relative to desired bedtime, without the need for costly and time-consuming circadian assessments.”

Associate Professor Sean W. Cain, in whose lab the work was done, said, “This marks an early advance in personalised “Circadian Medicine” where patients can be appropriately streamed for tailored treatment of diseases for which circadian dysfunction is a core feature.”

Read the full paper, “The pupillary light reflex distinguishes between circadian and non-circadian delayed sleep phase disorder (DSPD) phenotypes in young adults”, here.

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