A sleep study carried out by The University of Colorado, Boulder and reported in the Current Biology journal has found that participants who were deprived of sleep and then allowed to sleep for an unlimited period, failed to make up the time lost and that the practice of sleeping in on a weekend could even have a more detrimental effect on sleep cycles.
The study looked at 36 participants over a 13 night period, with all getting 8 hours sleep for the first three nights. 28 people then had their sleep limited to just 5 hours per night, while the rest kept to their usual 8 hours of sleep. Those who had limited sleep were then split into two groups – one was able to try and catch up on sleep over the weekend, while the other group was sleep deprived for a further 2 nights before being allowed to recover.
The group who were able to recover over the weekend slept in until around midday, with women getting up earlier than men. Despite this, the total number of hours of sleep lost was not made up. It was also found that the levels of the sleep hormone melatonin in this group was negatively affected compared to those who had consistent sleep patterns.
The entire group was also encouraged to eat whatever they wished after the first three nights. For those with a consistent 8 hours of sleep, bodyweight was unchanged; however those who were restricted in sleep had put on 1.5kg on average by the end of the study. It was thought that those who were sleep deprived tended to snack more in the evenings, disrupting their metabolism.
Co-author of the study Prof. Kenneth Wright has stated that sleeping in on a weekend could be just as bad or even worse than not doing so. He suggests that benefits of a lie-in could possibly be felt if sleep was inconsistent occasionally, but a constant yo-yo of sleep over the long term is probably going to do some harm.
This view is backed up by Dr Stuart Pierson, an expert in sleep and circadian clocks from the University of Oxford. He says that the data appears to show that these sleep cycles may cause metabolic consequences. However he points out that cognitive ability can be improved by naps among those who are sleep deprived.
Others have pointed out that the study is relatively small and short term.