Do you often struggle to make it to your 8.30 lectures because you couldn’t fall asleep until the early hours that morning? It would be difficult to find a student who answers no; we all sacrifice our morning lectures for a fun night out. Some will answer yes, not just due to nights out, but because they literally cannot fall asleep any earlier. It is not unusual to be unable to fall asleep at normal times. In fact, the national sleep foundation conducted a survey which concluded that 36% of the population experience a sleep problem.
One such sleep problem, with an estimated prevalence as high as 10% in the general population, is delayed sleep phase disorder (DSPD). It is the most commonly diagnosed circadian rhythm sleep disorder. DSPD can be characterised by a delay in sleep onset, or fragmented sleep patterns (brief period of sleep in the evening, supplemented by naps during the day). These misaligned sleeping patterns are the result of an altered circadian clock system.
36% of the population experience a sleep problem
The circadian clock system describes the internal control of an organism’s tissues and cells, resulting in a 24 hour cycle of many behavioral and psychological processes; sleep being one of these processes.
A study performed at The Rockefeller University, New York, recently identified that the altered circadian clock system, in the case of DSPD, is the result of a mutation in the CRY1 gene. CRY1 gene is core to the length of each circadian cycle. A gain of function mutation, resulting from deletion of exon 11, creates the DSPD gene variant CRY1Δ11. Expression of CRY1Δ11 leads to an altered function compared to the non-mutated CRY1 gene form. CRY1Δ11 causes the cellular circadian rhythm to be extended by 30 minutes. Although 30 minutes does not sound like a particularly large difference, this translates into a delayed sleep onset of 2-2.5 hours.
Of the 39 people in the study who have the CRY1Δ11 mutated gene variant, 38 reported either delayed sleep onset, or fragmented sleep patterns. The one outstanding participant reported a history of repeated sleep problems, but just not during the period of the study. This shows that the pattern of inheritance is autosomal dominant: you inherit two forms of each gene, one from each parent. The fact that it is autosomal dominant means that you only need to inherit CRY1Δ11 from one parent to experience DSPD. So if one of your parents suffers from DSPD, you have a 25% chance of also experiencing this yourself.
It is not all doom and gloom as there are many treatment options for those suffering from DSPD, ranging from bright light therapy to chronotherapy. Sometimes a strict sleep schedule can help; which sounds fairly easy, but means no lie-ins allowed on the weekends…