Melatonin receptor gene: Alzheimer’s risk and night shift work

Shift work and 'social jet lag' are linked to an increased risk for several chronic diseases. Shift work is usually defined in studies as working a late or early shift more than two times per week, while social jet lag is the term for staying up late and then sleeping in on the weekends in contrast to a sleep schedule that is hours earlier during the work-week.

How does shift work affect health?

Let me throw a few quick studies at you about the impact of shift work / social jet lag:
  • Solid research links shift work to an increased risk of cancer, specifically breast and prostate cancer[ref][ref][ref]
  • Shift work increases the risk of being overweight[ref][ref][ref]
  • It also increases the risk that your children will be overweight[ref]
  • Shift workers are at an increased risk for diabetes[ref][ref]
  • It also increases the risk of Alzheimer's and dementia[ref]
You may be thinking...I work the night shift and am just fine with it! Like most things, it turns out that genetics plays a role in how much shift work impacts you.

Variants in the melatonin receptor gene:

While some people may get along well with shift work, others may experience more difficulties with it. A new study found one genetic variant that may shed some light on the topic (pun intended :-). Scientists recently found that a melatonin receptor variant (MTNR1A gene) was associated with an increased likelihood of fatigue and other ill effects when working the night shift. The study looked at several different groups of night shift workers including flight attendants, pilots, and nurses. It found that those who carried the MTNR1A variant and worked the night shift more than were more likely to have higher fatigue scores. A control group that didn't work the night shift had no effect from the MTNR1A variant. The researchers believe this variant causes fewer melatonin receptors in the brain.[ref]

Is Alzheimer's disease linked to melatonin?

This same variant is also linked to an increased risk of Alzheimer's disease. In a cohort of those aged 85 and older, it was found that those with the rs12506228 A-allele were at about double the risk of Alzheimer's.[ref]

Related Article: Alzheimer’s and APOE genotype

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