Comparing expression levels of PERIOD genes PER1, PER2 and PER3 in chronic insomnia patients and medical staff working in the night shift

Sleep Med. 2020 Sep;73:101-105. doi: 10.1016/j.sleep.2020.04.027. Epub 2020 Jun 5.


Aim: This study was done to determine the changes in expression levels of PERIOD family genes in chronic insomnia patients and night shift healthcare staff with irregular sleep hours.

Method: A total of 24 chronic insomnia patients aged between 25 and 55 that were admitted to Erciyes University Medical Faculty Neurology Polyclinic, 32 medical staff aged between 23 and 42 that work in night shifts with no neurological diagnosis were included as volunteers in the experiment. Additionally, a control group consisting of 29 healthy individuals between 21 and 50 years of age who do not work in shifts was volunteered in the study. Since PERIOD family gene expressions are affected by time of day and season changes, blood samples were taken from the groups within the same week and at the same time periods. RNA isolation followed by cDNA synthesis from leukocytes was performed from blood samples that were kept in 10 cc EDTA tubes. Expression levels of the genes were then determined by quantitative PCR method and analysed.

Results: There was a significant decrease in the expression levels of PER1 and PER2 genes in chronic insomnia and night shift healthcare professional groups compared to the control group (p = 0.0001 for PER1; p = 0.0023 for PER2), but no significant change was observed in PER3 gene (p = 0.619).

Discussion: The decrease in PER1 and PER2 gene expressions in chronic insomnia and shift working healthcare personnel seems to be more of a result for short sleep periods than a cause.

Keywords: Chronic insomnia; Night shift; PER1; PER2; PER3; PERIOD genes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Circadian Rhythm
  • Gene Expression
  • Humans
  • Medical Staff
  • Middle Aged
  • Period Circadian Proteins / genetics
  • Period Circadian Proteins / metabolism
  • Sleep / genetics
  • Sleep Initiation and Maintenance Disorders* / genetics
  • Young Adult


  • PER1 protein, human
  • PER2 protein, human
  • PER3 protein, human
  • Period Circadian Proteins