"Scientists have discovered that our spinal discs have a 24-hour body clock that can cause … pain when it gets out of sync," the Daily Mail reports; overstating research limited to mice.

While the results may have human implications at some point in the future, the study does not demonstrate the effects of "a good sleep" on back pain in mice, let alone humans.

The researchers took cells from the intervertebral discs found in the spines of mice and people, and tagged them with bioluminescent genes which "pulse" in time with the circadian rhythms that govern the body's 24-hour clock.

They say that cells within the discs had their own "clocks" which were regulated by temperature. When they designed mice without these cellular clocks, their discs became damaged much faster than those of normal mice.

Back pain is a very common condition, likely to affect as many as 8 in 10 people. Damage to intervertebral discs – the cushions of fluid and cartilage that separate the bones of the spine – is thought to be a major cause of back pain. The researchers say that these discs thin out during the day, with the weight of our bodies, then expand again at night when we rest, with fluids regenerating the tissue.

The researchers said in a press release that getting a good night's sleep "will protect our body clocks and potentially avoid disc problems later in life." However, there's nothing in their study to prove that this is the case.



Where did the story come from?

The study was carried out by researchers from the University of Manchester and was funded by grants from organisations including the Medical Research Council, Arthritis Research UK and the Wellcome Trust.

The study was published in the peer-reviewed journal Annals of Rheumatic Diseases on an open-access basis, meaning it is free to read online.

The study was accompanied by a press release that made a number of optimistic speculations, such as "Based on our findings, we hope that one day, we may be able to combine NSAIDs with clock targeting compounds to provide a more powerful solution [to back pain]."

The Mail's headline took the press release one step further, suggesting that back pain can be beaten by a good night's sleep. While sleep is undoubtedly beneficial, back or other types of pain can prevent you from sleeping well, so this may not be a helpful message for sufferers. Further into the story, the Mail reported speculation from the study authors about the implications of their research for future treatment of back pain, and the possible effects of shift work on circadian rhythms.

What kind of research was this?

This was an experimental animal study, using mice bred for the purpose in a laboratory. Cells taken from human intervertebral discs were also used for one experiment, although we don't know where they came from (ie whether they'd been removed from people suffering back pain). The researchers wanted to look at the molecular and genetic activity within cells, to understand how circadian rhythms affected intervertebral discs.

These types of studies are useful to aid understanding of the basic science behind a disease. They're not tests of treatment for disease. Also, the results of animal studies don't always translate directly into humans.

What did the research involve?

Researchers carried out a number of experiments using cells taken from the intervertebral discs of mice and people. The experiments were designed to show whether cells had their own 24-hour clocks and how they were affected by external factors such as age, temperature and inflammatory chemicals.

In a separate experiment, live mice were bred without 24-hour clocks in their intervertebral disc cells, and were monitored for disc degeneration, compared to normal mice of the same age.

Researchers made the cells luminescent so they could track the activity within them, in line with daily rhythms. They stored the cells in containers where the temperature changed slightly at different times, to monitor their response to temperature.

They used two types of chemicals associated with inflammation – interleukin B and Tumor Necrosis Factor – to assess how these affected the 24 hour clocks. They compared the clocks' activity in cells from older and younger mice.

In the second experiment, they looked at the condition of discs of mice without 24-hour clocks in their disc cells after six months and 12 months, compared to normal mice.

What were the basic results?

The researchers say they showed that both mice and human disc cells had their own internal 24-hour clocks, demonstrated by their regular emission of pulses of light.

The cells became desynchronised when subjected to temperature changes at different times, suggesting that body temperature may be what "sets" the cells' clocks. Cells from older mice had a weaker 24-hour pattern than those from younger mice, reflecting the way that body clocks are known to weaken with age. The cells' body clocks were disrupted by interleukin B, suggesting that long-term inflammation could also cause body clock problems.

The discs of engineered mice without body clocks in these cells degenerated much faster than those of normal mice. Images of the discs after 12 months showed they were much thinner, had bony growths into the cartilage and signs of fibrosis in the tissue around the edges.

How did the researchers interpret the results?

In their paper, the researchers were fairly cautious, saying their results "support the notion that disruptions to circadian rhythms during ageing or in shift workers may be a contributing factor for the increased susceptibility to degenerative IVD (intervertebral disc) diseases and low back pain".

However, they went further in their press release, advising people to avoid night working and work regular hours. Of course, not everyone has the luxury of choosing what hours they work.

Conclusion

Back pain is a major problem for many people. Keeping active and taking painkillers when required can help, but some people find it significantly disrupts their lives. Knowing more about the causes of back pain may help doctors to find new ways to combat it, or even prevent it.

Experiments using cells and laboratory animals can help scientists to understand what affects the course of a disease at a cellular level. This may be of use in future to develop treatments. But until that work has been done, this study doesn't tell us what will actually help back pain sufferers.

We already know that shift work is linked to many chronic diseases, and that back pain seems more common among people who work night shifts. This research may help explain whether shift work contributes to back pain, but it doesn't prove that it's the cause. It's not necessarily helpful to tell people to avoid shift work to protect their spine – for some people, there is no alternative.

Getting a good night's sleep is good for health, whether it affects back pain or not. If you are having trouble sleeping, take a look at our information on how to sleep well.

Analysis by Bazian

Edited by NHS Website