March 18, 2007
Sleep Gene Determines Performance Of Sleep Deprived
Whether you can function well lacking sleep in the middle of the night might come down to the length of your copies of the PERIOD3 gene.
People are known to differ markedly in their response to sleep deprivation, but the biological underpinnings of these differences have remained difficult to identify. Researchers have now found that a genetic difference in a so-called clock gene, PERIOD3, makes some people particularly sensitive to the effects of sleep deprivation. The findings, reported by Antoine Viola, Derk-Jan Dijk, and colleagues at the University of Surrey's Sleep Research Center, appear online this week in the journal Current Biology, published by Cell Press.
There are two variants of the PERIOD3 gene found in the human population, encoding either long or short versions of the corresponding protein. Each individual will possess two copies of the gene, either of which might be the long or short form. Previous work had indicated that the different forms of the gene appear to influence characteristic morning and evening activity levels—for example, "owl" versus "lark" tendencies.
In the new work, a multidisciplinary research team consisting of biological scientists and psychologists compared how individuals possessing only the longer gene variant and those possessing only the shorter one coped with being kept awake for two days, including the intervening night. The researchers found that although some participants struggled to stay awake, others experienced no problems with the task.
The results were most pronounced during the early hours of the morning (between 4 and 8 a.m.), during which individuals with the longer variant of the gene performed very poorly on tests for attention and working memory.
But how do the carriers of the short and long versions perform during the day when they have plenty of sleep?
Carriers of the longer version spent a larger portion of their sleep time in the deepest sleep state. My guess is that confers some sort of advantage. Any idea what that advantage might be?
An additional finding was that the effects of this gene on performance may be mediated by its effects on sleep. When the volunteers were allowed to sleep normally, those possessing only the longer form of the gene spent about 50% more of their time in slow-wave sleep, the deepest form of sleep. Slow-wave sleep is a marker of sleep need, and it is known that carrying a sleep debt makes it very difficult to stay awake and perform at night.
What I'd like to know: Do the people with the longer form of the gene form more memories when they sleep? I ask this because if there are two versions of the gene widespread then likely each version provides advantages and disadvantages. What advantage does the long version provide that compensates for its disadvantages when one stays up all night?
When offspring genetic engineering becomes possible prospective parents are going to be faced with thousands or even tens of thousands of trade-offs between different genetic variations for their offspring. Make your kid a night owl? Or make him wake up at the crack of dawn? Make your kid able to handle lots of sleep disruptions and get by on less sleep? Or perhaps make her brain age more slowly or form more memories per time asleep?
One evolutionary disadvantage of people possessing the longer form of the gene may be that those who sleep more deeply are less likely to notice their neighbor sneaking into the house to steal their cache of grain or to slit their throat.
Well - I certainly possess the "long" gene in this case - so feel free to ask away.
I feel that I have an above average memory of facts and figures - although I also have OCD which causes me to read compulsively.
My retention rate of the material I read is quite good imho.
I have found that my inability to function without sleep is - at times - an unfortunate issue but I simply learned to avoid the normal "all nighters" at college as they actually caused me to perform worse on tests - particularly those early in the day.
As for the grain scenario above - it is actually something I am concerned with from time to time - my only solution has been to use a normal household alarm system backed up with a secondary master bedroom intrusion alarm.
I also have been known to keep close combat weapons near my side of the bed knowing that my condition may leave me with little time to react.
And - despite my antisocial tendency to stay up late - I would not be inclined to trade my disposition - I rather enjoy the relative solitude of the dark evening hours.
I can relate to Lono above. I pretty sure I have two copies of the long version; I do horribly with even mild sleep deprivation (say a few days of only sleeping 6 or even 7 hours).
Also, many people consider themselves "morning" or "night" people. I am a definite "neither." I have a hard time both staying up late and getting up early...if I get up early at all, I am very tired, and become very tired again early. If I stay up late, I both feel tired when I am trying to stay up late and struggle to get up even after 8-9 hours of sleep (i.e. if I go to bed at 12 midnight, I have a hard time even getting up at 8 or 9 the next morning).
With enough sleep deprivation, I feel very tired even after massive amounts of stimulants (e.g. a strong cup of coffee, both cigarette and dip tobacco, and 200-500mg of dextromethorphan ("non-drowsy" R0b1tuss1n max cough/DM), which acts strongly at the same primary receptors as R1t@lin and cocaine (i.e. PCP2 and sigma1)).
I'm not so sure that the longer form necessarily has to confer an advantage to be maintained in the species. I'm no geneticist, but it seems that there a lot of minimally advantageous traits which are nevertheless maintained, especially in the easygoing world of today.
On another note, I would definitely say I have the short-form. Otherwise I'm operating very badly all the time.
The long form would confer advantages for strength building and wound healing while possibly having a negative impact on memory. Memory is fixed during REM sleep which is a lighter sleep cycle. Growth and healing occur mostly during the deep cycles.
Having a mix of the four genotypes would improve the genetic fitness of a paleolithic community by providing a good mix of people to act as sentries at different times of the day.
That would perhaps explain my small, scrawny frame. :p