Could There Be a Genetic Advantage for Some Shift Workers Over Others?

The results of important research into nurses employed at Vanderbilt University Medical Center doing shift work, was published on April 13, 2011.

Most interestingly, a number of genes appear to have an impact on the effectiveness of the sleep deprivation strategy that some nurses use when they change shifts.

The study recognized that the daily circadian rhythm, hormones and physiological processes are often misaligned during shift work leading to increased risk of a number of adverse conditions including cardiovascular disorders, metabolic disorders, gastrointestinal disorders, some types of cancer, and mental disorders.   The study assessed 388 workers on the effects of factors such as chronotype and genotype on the nurses’ adaptability to changes in shift times, etc.

Graphs have been produced showing the percentage of workers ‘not well adapted’ to changes in shift, depending on their sleep strategies when their shift times were changed.

Sleep Deprivation

I suppose it wasn’t too surprising to find that the nurses who used sleep deprivation to get themselves ready for their next shift were the least well adapted, but I wasn’t expecting the early morning larks to have a more extreme attitude to their shift times than the night owls.

The larks were found to adapt particularly well to day shifts, and particularly poorly to night shifts, but the owls didn’t adapt particularly poorly or well to either shift.


Genetics did make a difference.  The research results published on the website states that polymorphisms (more than one form, or morph) in the genes CLOCK, NPAS2, PER2 and PER3 “were significantly associated with outcomes such as alcohol/caffeine consumption and sleepiness, as well as sleep phase, inertia and duration in both single- and multi-locus models.  Many of these results were specific to shift type suggesting an interaction between genotype and environment (in this case, shift work).”

The study found that variants in one gene, PER3, appeared to have a major impact on the effectiveness of the ‘no sleep’ strategy.  The Science Daily reported that “individuals with one variant of this genotype appear to respond more poorly than average to the strategy while those with the other genotype appear to respond better than average.”

The most common approach used by about half of the workers when changing shifts was to sleep in late on the morning before their first shift.  The sleep deprivation strategy was the second most common strategy, meaning that they skipped sleep for at least 24 hours straight.  Of course this has to affect the accuracy of the work they are doing, not just their own health, but that was beyond the scope of the study.

This study has contributed valuable information to shift workers trying to minimize the effects of their constantly changing body clocks, and the effect sleep deprivation is having on their health and mental attitude.

This is the first study of its kind to identify and characterize human behavior, especially one that has an effect on human health, according to the co-author Chris Ciarleglio.

For more information on the study visit:

And a practical and valuable conclusion that came out was also to not change shifts very often if it can be avoided.  And the best adapted shift types were the “Incomplete Shifter (IS)” where the shifts did some kind of overlap in times, not jumping radically from the last.  (Refer to the graphs in the reference above.)