A melatonin receptor gene may influence how well a person tolerates shift work, according to a new Finnish study. The findings may help explain why some people adapt easily to shift work, while others seem to struggle with chronic exhaustion or sleep disorders.
Approximately 37 percent of shift workers do not get enough sleep due to their work schedule, according to the National Sleep Foundation. Furthermore, around 10 percent of night and rotating shift workers experience sleep disorders, such as insomnia or daytime fatigue.
The study, published in the journal Sleep, is the first to systematically examine the genetic factors underlying poor tolerance to shift work. The researchers analyzed the genomes of shift workers who were involved in the Health 2000 Survey, a nationally representative survey conducted between 2000-2011. The survey involved more than 8,000 individuals aged 30 and older residing in mainland Finland.
The research was led by Professor Tiina Paunio and involved Finnish shift workers from many different lines of work. The differences in the job-related exhaustion reported by employees were contrasted with genetic differences in their entire genome.
Covering the entire genome, the research team found that a common variation in the melatonin receptor 1A (MTNR1A) gene is linked to the job-related exhaustion commonly experienced by many shift workers.
The study also established that the risk variation of the melatonin receptor 1A (MTNR1A) gene is probably related to the methylation of DNA in the MTNR1A gene. The methylation of DNA is one of the mechanisms that helps regulate the function of the genome. This is influenced not only by variations in DNA sequence but also through environmental factors such as fluctuations in the circadian rhythm.
Since the DNA methylation results in a smaller number of melatonin receptors, it can cause weaker natural melatonin signaling, one of the regulatory mechanisms in stabilizing the circadian rhythm.
The influence of the risk variant of the MTNR1A gene may explain the degree to which light exposure at night disrupts the circadian rhythm of shift workers.
“These findings suggest that a variant near MTNR1A may be associated with job-related exhaustion in shift workers,” say the authors. “These results could indicate a link between melatonin signaling, a key circadian regulatory mechanism, and tolerance to shift work.”
The researchers still offer a word of caution, however, when interpreting the findings. “The variant we have now discovered can only explain a small part of the variation between individuals, and it cannot be used as a basis to determine a person’s tolerance to shift work,” Paunio points out.
Source: University of Helsinki