Circadian clock gene variants and insomnia, sleepiness, and shift work disorder

Shift workers often experience circadian misalignment and problems adjusting adequately to their work schedules, which is manifested in the high prevalence rates of shift work disorder, insomnia and sleepiness in this group of workers compared to day workers. However, there exist large inter-individual differences in tolerance to shift work. We investigated whether frequency variation in single nucleotide polymorphisms capturing genetic variation in genes involved in the regulation of circadian rhythms (clock genes) was associated with insomnia, sleepiness, and shift work disorder in a sample of Norwegian nurses employed in various work schedules. Saliva samples from 691 female nurses participating in “the Survey on Shift work, Sleep and Health” were analysed for associations between genetic variations in clock genes and the nurses’ survey responses. A total of 662 single nucleotide polymorphisms were analysed. After multiple testing correction, we did not observe any statistically significant associations between the genetic variants and insomnia, sleepiness, or shift work disorder.