Does the Moon affect Joint Pain?

I have been attending to some patients referred to me for pain management. Most of the patients who visit an Anesthesiologist at the OPD clinic for pain problems usually suffer from chronic pain; from Rheumatoid arthritis to Osteoarthritis and so on. 

With the advent of various medications, nerve blocks and therapies most of the pain intensity can be fairly controlled. However, a patient suffering from a chronic condition often has a complete to near complete pain-free period interspersed between periods of exacerbations when the pain intensity is beyond control of usual routine medications and require top up therapy. 

During one of my OPD attendees was a middle aged male of 40 years who had been living with seronegative Rheumatoid Arthritis over the past 5 years. He was on DMARDs (Methotrexate 15mg weekly and Sulfasalazine 1 gm daily) along with Folic Acid supplementation with which his disease was under fair control. 

However, he visited me on one occasion with an acute exacerbation of his condition and he rated his pain as an 8 out of 10. As an initial therapy NSAID and Paracetamol were prescribed which provided him adequate relief and he was at ease. But he returned to the clinic with another exacerbation after four weeks. While taking the clinical history, he mentioned that the moon brought on his pain. On further probing he revealed that he felt as if his pain was worse on near-full moon and full moon nights. He informed us that it had been like this over the last six months with an accuracy of +/-2 to 3 days when he considered the severity of his pain with the phase of the moon (Full moon night) 

His case was intriguing and so I decided to enquire other patients who presented with chronic pain of more than a year duration if they had also had a similar predicament. Surprisingly four out of fifteen patients had observed such an event. As the weeks passed with the passage of the next full moon another three patients also reported an exacerbation of their pain. However I decided not to consider these three cases as I had a feeling that discussion about the phase of moon and pain might have biased their opinion. 

Back from the chamber I enquired some of my fellow colleagues if they had similar cases but a mixed opinion arose out of the discussion. Some of them laughed it off while some justified it with the moon’s gravity. Internet research also gave a mixed opinion. While some felt that brighter nights led to less melatonin and hence more time needed to fall asleep coupled with more instances of break in the night time sleep that led to increased intensity of pain (1) but such claims on sleep quality was refuted by others (2). Some others postulated that the moon’s enhanced gravitational pull on full moon nights which led to synovial capsule stretching that led to enhanced sensation of pain from the damaged tissues because of the pull. The justification was that gravity was an important factor affecting the closed synovial cavity (3,4). 

In a large study (PAIN OUT) involving 10 international hospitals participating in the research project, 12,224 patient data sets were assessed where hospitalized patients were asked for their pain after surgery and pain treatment side effects using numerical ratings scales from 0 to 10. Kurskal–Wallis H-tests were applied to find out if the four moon phases had any significant outcome differences. The only items that show statistically significant differences were pain interference with sleep and drowsiness. The most effected sub-groups that showed statistically significant connections to lunar phases in some variables were men and elderly people (5). 

In a study from NASA where effect of microgravity on cartilage homeostasis was studied it was found that the combined effects of radiation and microgravity simulated exposed chondrocytes to undergo morphological rearrangement of the actin cytoskeleton. Gene expression analyses confirmed that cells exposed to both radiation and simulated microgravity express more collagen I and less collagen II and aggrecan, which is characteristic for de-differentiated chondrocytes (6).

Therefore, variability of opinion and research findings on the various aspects of the subject may be narrowed down by further research on the topic.

References:

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1.	Cajochen C, Songül AE, Mirjam M, al e. Evidence that the Lunar Cycle Influences Human Sleep. Current Biology. 2013; 23(15): p. 1485–1488.
2.	Haba-Rubio J, Marques-Vidal P, Tobback N, al e. Bad sleep? Don't blame the moon! A population-based study. Sleep Med. 2015; 16(11): p. 1321-6.
3.	[Online]. Available from: https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/joints-8/synovial-joints-92/stability-and-range-of-motion-at-synovial-joints-519-323/.
4.	Mcminn. Last's Anatomy: Regional and Applied. In.: Elsevier Australia; 2003. p. 542.
5.	Komann M, Weinman C, Meissner W. Howling at the moon? The effect of lunar phases on post-surgical pain outcome. Br J Pain. 2014; 8(2): p. 72–77.
6.	[Online]. Available from: https://lsda.jsc.nasa.gov/scripts/experiment/exper.aspx?exp_index=13806.

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