Melatonin, Alzheimer's Risk, and Working the Night Shift

Key takeaways:

Altered circadian rhythm from working a late shift or even just staying up late on the weekends affects your health in multiple ways.
Studies show that shift work or social jetlag can increase cancer risk, cause weight gain, or even increase Alzheimer’s risk.
Your genetic variants in melatonin receptor genes may interact with shift work to increase your risk of negative health consequences.

How does shift work affect health?

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.

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 :-).

Ill-effects from shiftwork:
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 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]

Long-term effects:
A 2026 study involving more than 14,000 people showed that the negative effects of shift work persist even after retirement. Moreover, workers who had the MTNR1A variant (in the genotype report below) had a significantly exacerbated effect from past shift work.[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

MTNR1A Genotype Report:

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Lifehacks

How to increase melatonin at night:

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 various 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.

Melatonin supplements?
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.

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Related Articles and Topics:

Genetic Mutations that Protect Against Alzheimer’s Disease

References:

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