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.
Melatonin Receptors and Shift Work:
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.
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]
This same variant is also linked to an increased the 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]
MTNR1A Genetic Variant
- A/A: likely fewer melatonin receptors in the brain, a greater impact from working the night shift, increased risk of Alzheimer’s. [ref] [ref]
- A/C: somewhat fewer melatonin receptors, somewhat impacted from light at night, increased risk of Alzheimer’s
- C/C: normal MTNR1A variant
Members: Your genotype for rs12506228 is —.
The researchers think that the reason that the variant increases the risk for Alzheimer’s and the fatigue from shift work is due to a decrease in the number of melatonin receptors in the brain. Specifically, a decreased number of melatonin receptors in the suprachiasmatic nucleus may be causing increased sensitivity to light at night.[ref]
Blocking blue light at night:
Light at night is listed by the World Health Organization as a probable carcinogen, and even dim light at night is tied to a variety of diseases.
Blue-light blocking glasses are a great option for increasing your natural melatonin at night. Blocking out the blue wavelengths for a couple of hours before bed has been shown in several studies to increase melatonin levels within a week.
Blackout curtains are wonderful for blocking out dim light from streetlights and neighborhood light pollution. Also be sure to eliminate any sources of light (led indicator lights, night lights, etc) in your bedroom so that you can sleep in the dark.
Researchers have been looking at the connection between melatonin and Alzheimer’s with animal studies and trials of melatonin for preventing Alzheimer’s. The research is exciting and something to keep an eye on.
More to read:
- New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation
- Melatonin Attenuates Memory Impairment, Amyloid-β Accumulation, and Neurodegeneration in a Rat Model of Sporadic Alzheimer’s Disease.
- Melatonin Treatment Enhances Aβ Lymphatic Clearance in a Transgenic Mouse Model of Amyloidosis.
Please note: I realized after reading back through this article that it makes shift work seem very negative. I just wanted to comment that I’m totally grateful for all of our policemen, first responders, hospital workers, military personnel, etc. who are working the night shift, keeping us safe. Hopefully, this article will give a few ideas on how to mitigate the effects of long-term shift work.