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NHS Choices: Behind the headlines   + / -  
last updated: Mon, 27 Apr 2015 19:42:06 GMT

 Mon, 27 Apr 2015 12:00:00 GMT Having a spine similar to a chimp could lead to back pain

"People with lower back problems are more likely to have a spine similar in shape to the chimpanzee," BBC News reports. Research suggests that humans with similar shaped vertebrae to chimps are more vulnerable to developing a slipped disc.

Back pain is a common problem that affects most people at some point in their life and is one of the leading causes of what is known as a slipped disc – when one of the discs that sit between the bones of the spine (the vertebrae) is damaged and presses on the nerves.

But our knuckle-walking ape cousins don’t suffer nearly as much. One explanation is that our back problems are due to the extra stress placed on our backs from standing upright.

Scientists studying the vertebrae of chimpanzees, medieval humans and orangutans found humans with disc-related back problems had spines more similar in shape to chimpanzees.

Back problems in this study were defined as the presence of a lesion called a Schmorl's node; they are most often seen in people who have a slipped disc and can be a general sign of degeneration in the spine, though their significance is not completely understood. The participants, however, were long dead, so we don’t actually know if they had back pain.

The researchers think this knowledge could be used to identify people who are more likely to have back problems, based on the shape of their spines. This is plausible, but not yet a reality.

Where did the story come from?

The study was carried out by researchers from Universities in Canada, Scotland, Germany and Iceland. It was funded by the Social Sciences and Humanities Research Council, Canada Research Chairs Program, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, MITACS, and Simon Fraser University.

The study was published in the peer-reviewed science journal BMC Evolutionary Biology. This is an open-access journal, so the study is free to read online.

Generally, the UK media reported the story accurately, avoiding the common pitfall of saying, or implying, that humans have evolved from chimps. This is not the case. We both have a common ancestor, so are cousins, albeit cousins who shared a grandparent 5-10 million years ago.

Many articles suggested that the finding may help identify people at a higher risk of back pain, such as athletes. However, any implications from this study are not completely clear, and we don’t yet know how useful this knowledge would be in practice.

 

What kind of research was this?

This was an evolutionary study looking at the spines of human and non-human primates to see how differences might relate to back problems.

Back pain is a common problem that affects most people at some point in their life. However, our ape cousins don’t suffer nearly as much. One explanation is that our back problems are due to the extra stress placed on our backs from standing upright. Non-human apes don’t walk upright nearly as much as humans.

Our ape ancestors' vertebral shape would not have been adapted for walking upright. Because of this, the research team predicted that people whose vertebrae were at the more ancestral end of the range of shape variation can be expected to suffer disproportionately more from load-related spinal disease.

 

What did the research involve?

The last thoracic (upper back) and first lumbar (lower back) vertebrae from 71 humans, 36 chimpanzees and 15 orangutans were scanned using computers and compared in detail for subtle differences in their shape and position of bony landmarks.

The human vertebrae were from skeletons dug up from the medieval and post-medieval period, while chimpanzee and orangutan vertebrae were a mix of wild and zoo animals from US Natural History museums.

Of the human vertebrae, about half had Schmorl’s nodes, and half did not. The spine is made up of stacks of bone (vertebrae) and discs (cartilage), making the spine both strong and moveable. The nodes are small bulges of the cartilage disc into the adjacent bony vertebrae.

They are most often seen in people who have a slipped disc and may be a general sign of degeneration and inflammation in the spine.

However, the nodes' significance in slipped discs and back pain is not completely understood. For example, some people who have them have pain, while others do not. For the purposes of this research, vertebrae with the Schmorl’s nodes were referred to as “diseased” and those without referred to as “healthy”. None of the non-human ape vertebra were classed as diseased.

They fed all the information into a statistical model to predict spine health for human and non-human apes.

 

What were the basic results?

The predictive model was able to show there were differences in the vertebrae in healthy humans, chimpanzees and orangutans. Crucially, it found no difference between diseased human vertebrae and chimpanzees.

This suggested that humans with Schmorl’s nodes are closer in shape to chimpanzee vertebrae than healthy human vertebrae.

 

How did the researchers interpret the results?

The research team concluded: "The results support the hypothesis that intervertebral disc herniation [a "slipped disc"] preferentially affects individuals with vertebrae that are towards the ancestral end of the range of shape variation within H. sapiens [modern humans] and therefore are less well adapted for bipedalism [walking upright on two legs]. This finding not only has clinical implications, but also illustrates the benefits of bringing the tools of evolutionary biology to bear on problems in medicine and public health."

 

Conclusion

This evolutionary research used a small sample of vertebrae from humans, chimpanzees and orangutans to show that people with a disc bulge had spines more similar in shape to chimpanzees than healthy humans. The research team took this as a sign that people with vertebrae shape more similar to chimpanzees may be more likely to have disc-related back problems because they are less well adapted, evolutionary speaking, to walking upright.

The main limitation of the study is the use of Schmorl’s nodes to label spines as "diseased" vs. "healthy", and to assume the presence of the nodes was a sign of back pain. Obviously, the skeletons could not be asked whether they experienced back pain. The significance of Schmorl’s nodes is still not completely understood. Not everyone with them has back pain, so the results are less widely applicable than they may appear.

The study also used a relatively small number of vertebrae to reach its conclusions. The reliability of the findings would be improved if they were replicated using more vertebrae.

The implications of the study were summed up by lead scientist Dr Kimberly Plomp, in The Daily Telegraph, who said: "The findings have potential implications for clinical research, as they indicate why some individuals are more prone to back problems … This may help in preventative care by identifying individuals, such as athletes, who may be at risk of developing the condition."

This may be possible, but at this stage in the research, we can’t draw any firm conclusions.

The study isn’t applicable to all back pain, only those related to specific disc bulges. The findings are not relevant to the large number of people with general mechanical back pain, without specific cause, or to people with other disease or injury causes of back pain.

For advice on how to prevent and treat back pain, visit the NHS Choices Back Pain Guide.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

Lower back pain linked to chimpanzee spine shape. BBC News, April 27 2015

Back pain sufferers may have 'vertebrae like apes'. The Daily Telegraph, April 27 2015

Back pain 'linked to chimpanzee ancestors'. ITV News, April 27 2015

Links To Science

Plomp KA, Viðarsdóttir US, Weston DA, et al. The ancestral shape hypothesis: an evolutionary explanation for the occurrence of intervertebral disc herniation in humans. BMC Evolutionary Biology. Published online April 27 2015

 Mon, 27 Apr 2015 12:00:00 GMT Parents 'may pass anxiety on to their children'

The Mail Online has given stressed-out parents one more thing to worry about, saying: "Anxiety is 'catching' and can be passed on to children", adding that, "Attitudes of over-anxious parents can severely affect children's behaviour".

The study that prompted these headlines used an interesting "children of twins" study design intended to filter out the influence of genetics, which is known to have an effect on anxiety.

To do this, researchers studied patterns of anxiety in families of identical twins, who are genetically identical, and in families of non-identical twins.

They found there was some link between anxiety and neuroticism (a tendency to have negative thought patterns) in parents and their adolescent children.

There was no evidence that genetics was playing a significant role, but modest evidence that non-genetic factors were. This suggested that anxiety, far from being hardwired into DNA, might be passed on in other ways, such as through learned or mimicked behaviour.

In the Mail Online, journal editor Dr Robert Freedman said: "Parents who are anxious can now be counselled and educated on ways to minimise the impact of their anxiety on the child's development."

This suggestion seems a touch premature – as noted by the researchers, there is a chicken and egg situation here that has not been resolved. Do children worry because they sense their parents are worried, or do parents worry because they see their children are worried about something? 

Family life is not always easy, but one way to boost your physical and mental health is to make the time to do activities as a family

Where did the story come from?

The study was carried out by researchers from universities based in London, Sweden and the US. It was funded by the Leverhulme Trust, the US National Institute of Mental Health, and the National Institute for Health Research.

The study was published in The American Journal of Psychiatry, a peer-reviewed medical journal. It has been made available online on an open-access basis, so it is free to read or download as a PDF.

Generally, the Mail Online reported the story accurately, but hardly mentioned the study's limitations. The quote from journal editor Dr Robert Freedman saying that, "Parents who are anxious can now be counselled and educated on ways to minimise the impact of their anxiety on the child's development", seems a little premature, based on the relatively weak associations found in this research.  

What kind of research was this?

This twin study investigated the relative role of genetic factors (nature) and non-genetic factors (nurture) in the transmission of anxiety from parent to child.

Non-genetic factors might be, for example, the children observing their parents' anxious behaviours and mimicking them, or the parenting style of anxious parents.

The researchers say it is well recognised that anxiety can run in families, but the underlying processes are poorly understood. This study wanted to find out whether genetics or environment was more important in the transmission of anxiety, by observing identical twins.

This type of study is commonly used for this type of question. It does not aim to pinpoint exact genes or non-genetic factors that play a role in a trait. 

What did the research involve?

The team gathered self-reported anxiety ratings from parents and their adolescent children. They compared the results between identical twin families and non-identical twin families to see to what extent non-genetic factors were driving anxiety transmission, in contrast to genetics. 

Data came from the Twin and Offspring Study of Sweden, which has information on 387 identical (monozygotic) twin families and 489 non-identical (dizygotic) twin families. A twin family comprised a twin pair where both twins were parents, each twin's spouse, and one of each of their adolescent children.

In families where the twins were identical, the cousins would share, on average, 50% of the same DNA with their (blood) aunt or uncle. In families where the twins were not identical, the cousins would share less of their DNA, on average, with their aunt or uncle.

If cousins whose parents are identical twins are more similar to their aunt or uncle for a trait than cousins whose parents are non-identical twins, this suggests that genes are playing a role.

Only same-sex twin pairs were used. Twin offspring were selected, so cousins were the same sex as one another and did not differ in age by more than four years, so they were as similar as possible. The average age of the twin offspring was 15.7 years.

This type of study design, known as a "children of twins" study, is intended to dampen down the potential influence that family genetics could have on the outcomes being investigated.

Anxious parental personality was self-reported using a 20-item personality scale. They rated phrases such as, "I often feel uncertain when I meet people I don't know very well", and, "Sometimes my heart beats hard or irregularly for no particular reason".

Each item was ranked between 0 (not at all true) and 3 (very true), covering social and physical signs of anxiety, as well as general worry. There was a similar self-reported scale to measure neuroticism.

Offspring anxiety symptoms – social, physical and general worry – were measured in a similar way, using questions from a Child Behaviour Checklist.

Both parents and offspring rated their anxiety and neuroticism over the last six months. The researchers used computer modelling of the relationships between individuals and their traits to estimate the contribution of genetic and non-genetic factors. 

What were the basic results?

Analysis of the data suggested genetic factors were largely not driving the transmission of anxiety or neuroticism from parent to adolescent. Ratings of anxiety and neuroticism within and between twin families were only very weakly linked.

However, there was "modest evidence" that non-genetic transmission of both anxiety and neuroticism was happening. Although still a relatively weak relationship, it was statistically significant, unlike the genetic finding. 

How did the researchers interpret the results?

The research team said their results supported the theory that direct, environmentally mediated transmission of anxiety from parents to their adolescent offspring was the main driver, and not genetics.   

Conclusion

This study tentatively shows that environmental factors, as opposed to genetics, play a more important role in the transmission of anxiety from parents to their adolescent children.

However, it used self-reported anxiety ratings over a six-month period, so this tells us very little about any potential longer-term effects of anxiety transmission while growing up.

The correlations in the main results were quite weak. This means that not every adolescent with an anxious parent will "catch" or "take on" their parents' anxiety. This suggests that it's a more complex issue.

The results showed non-genetic (environmental) factors were more important than genetic, but precisely what these environmental factors were is not something this study can tell us.

The study used a clever and unique sample of twins and their families to drill down into the age-old debate about the influence of nature versus nurture. However, it doesn't prove that environmental factors are the main driver overall.

That notwithstanding, the authors suggest two main contrasting explanations for the results:

  • parental anxiety causes their children to be more anxious – this could happen through different learning and mirroring behaviours known to occur when children and adolescents grow and develop; for example, an adolescent witnessing repeated examples of parental anxiety may learn that the world is an unsafe place that should be feared
  • anxiety in the offspring influences the parenting they receive – the flipside is that a teenager showing anxious behaviour may cause their parents to worry; the research team add that this might in turn worsen the anxiety in the teenager, creating a negative feedback loop

This twin study doesn't bring us any closer to knowing which explanation might be true, or to what extent this can be impacted by changes in behaviour.

Despite these limitations, the hypothesis that children are sensitive to their parents' attitudes and mood seems plausible. So, learning more about how to manage your stress and feelings of anxiety could be good for both you and your children.

For more information and advice, visit the NHS Choices Moodzone.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

Anxiety is 'catching' and can be passed on to children, scientists warn over-protective parents. Mail Online, April 24 2015

Links To Science

Eley TC, McAdams TA, Rijsdijk FV, et al. The Intergenerational Transmission of Anxiety: A Children-of-Twins Study. The American Journal of Psychiatry. Published online April 2015

 Fri, 24 Apr 2015 12:45:00 GMT Gene editing technique could prevent inherited diseases

“Researchers in the US have raised hopes for a simple genetic therapy that could prevent devastating diseases being passed on from mothers to their children” The Guardian reports.

The diseases in question are caused by mutations in the small pieces of DNA found in the powerhouses of the cells – the mitochondria. This DNA is passed directly from mother to child.

Mitochondrial diseases can cause symptoms including muscle weakness, seizures and heart disease – and have reduced life expectancy.

One option to treat this, as we have discussed several times, is so-called “three-parent” IVF, where unhealthy mitochondria are effectively replaced by healthy mitochondria from a donor egg.

This new technique from the US may eventually offer an alternative approach.

The researchers developed a way to target and break down mutated mitochondrial DNA. They found that they could successfully use this technique in mouse eggs. Once fertilised, these eggs could go on to produce healthy and fertile mice, with little of the targeted mitochondrial DNA in their cells. The technique also seemed to work on hybrid mouse-human cells carrying human mitochondrial DNA mutations in the lab.

This new technique is of interest because if it were effective and safe in humans, it could offer a way to prevent mitochondrial diseases without the need for the donor egg. The research is at an early stage, and many questions remain that need to be answered through future studies before this technique could be considered for testing in humans.

 

Where did the story come from?

The study was carried out by researchers from the Salk Institute for Biological Studies and other research centres in the US, Japan, Spain and China.

The researchers were funded by the Leona M. and Harry B. Helmsley Charitable Trust, the US National Institutes of Health, National Basic Research Program of China, Chinese Academy of Sciences, National Natural Science Foundation of China, the JDM Fund, the Muscular Dystrophy Association, United Mitochondrial Disease Foundation, the Florida Department of Health and the G. Harold and Leila Y. Mathers Charitable Foundation.

The study was published in the peer-reviewed scientific journal Cell on an open-access basis, so the study is free to read online.

Both the Guardian and The Independent cover this research reasonably. One quote from a study author suggests that: "the technique is simple enough to be easily implemented by IVF clinics around the world", but it is important to realise that much more research is needed to make sure the technique is effective and safe before it could be tested in humans.

 

What kind of research was this?

This was laboratory and animal research aiming to develop a new way of preventing transmission of mutations in the mitochondrial DNA. This research is appropriate for the early development of new techniques, which may eventually be used to treat human disease.

While most of our DNA is found in a compartment of our cells called the nucleus, there is some DNA within the cell’s many mitochondria. These are the energy producing "powerhouses" of the cells. Mutations in this DNA can cause a range of serious diseases affecting the organs that need a lot of energy – such as the brain and muscles.

We inherit our mitochondria from our mothers. Researchers have developed techniques to avoid passing these mutations on, involving transferring the DNA from the mother’s nucleus into a donor egg. Manipulation of human embryos is tightly controlled in the UK, and after much debate, the government recently agreed to make it legal to perform these "three-parent IVF" techniques to prevent mitochondrial diseases.

One concern with these techniques is that the child inherits mitochondrial DNA from a third person (the egg donor). The current research aimed to develop a different technique to avoid passing on mitochondrial mutations that does not involve a donor egg. It is specifically aimed at women who have a mixture of mitochondria in their cells – some carrying a disease-causing mutation and some not.

 

What did the research involve?

The researchers developed a technique to reduce the amount of mutation carrying mitochondrial DNA. This involved injecting into the cells genetic instructions for making a protein to be sent to the mitochondria and cut the mitochondrial DNA in a specific place. They first tested this technique on mouse egg cells that carried a mixture of two types of mitochondrial DNA, one of which could be cut by the protein (the "target" mitochondrial DNA) and one which could not. They then checked to see if it could reduce the amount of “target” mitochondrial DNA.

They then tested it on fertilised "mixed mitochondrial DNA" mouse egg cells to see if it had the same effect and whether it affected development of the embryo. They also implanted treated embryos into host mother mice to see if the offspring were born healthy and how much of the target mitochondrial DNA they carried.

Finally, they modified their technique slightly so they could use it against human mitochondrial DNA carrying disease-causing mutations. After testing this adapted technique in mice, they tested it on cells in the lab containing human mitochondria with mutations that caused one of two different mitochondrial diseases:

  • Leber’s hereditary optic neuropathy and dystonia (LHOND)
  • neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP)

These are both rare conditions in humans that cause symptoms affecting the muscles, movement and vision.

These hybrid cells were created by fusing mouse egg cells and human cells carrying the mitochondrial mutations.

 

What were the basic results?

The researchers found that their technique reduced the amount of the target type of mitochondrial DNA in the "mixed mitochondrial DNA" mouse egg cells. Their technique performed similarly in fertilised embryos from these eggs. These embryos appeared to develop normally in the lab when examined under a microscope. The technique did not appear to affect the DNA in the mice’s nuclei.

When the treated embryos were implanted into host mothers, the offspring born also had much less of the target type of mitochondrial DNA throughout their bodies. They appeared to be healthy and develop normally in the tests performed, and could themselves produce healthy offspring. These offspring had such low levels of the target type of mitochondrial DNA that it was barely detectable.

The researchers were able to adapt their technique to target human mitochondrial mutations. It reduced the amount of mitochondrial DNA containing the LHON or NARP mutations in hybrid egg cells in the lab.

 

How did the researchers interpret the results?

The researchers concluded that their "approaches represent a potential therapeutic avenue for preventing the transgenerational transmission of human mitochondrial diseases caused by mutations in [mitochondrial DNA]".

 

Conclusion

This early research has developed a new technique to reduce the amount of mutation-carrying DNA within mitochondria. The hope is that this technique might be used in the eggs of women carrying disease-causing mitochondrial mutations.

The government has recently given the go ahead for a technique that allows a woman who carries such a disease from passing it on to her child – making the UK the first country to do so.

This technique has raised some ethical and safety concerns, as it places the woman’s chromosomes into a donor egg with healthy mitochondria. This means that once this egg is fertilised it contains DNA from three people – the DNA in the nucleus comes from the mother and father, and the mitochondrial DNA comes from the egg donor.

This new technique is of interest because if it were effective and safe in humans, it could offer a way to prevent mitochondrial diseases without the need for the donor egg. This technique shows promise, but is still in its early stages. It has thus far only been tested in mice, and in human-mouse hybrid egg cells carrying mutated human mitochondria in the lab.

It is also specifically aimed at women who have a mixture of normal and mutated mitochondrial DNA, as it relies on the normal mitochondrial DNA being there to "take over" once the mutated DNA has been reduced. It would not work in women who have only mutated mitochondria, and there may be a certain level of normal mitochondrial DNA that needs to be present for the technique to work.

All of these issues are likely to be investigated in future studies.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

Hopes raised for new genetic therapy to prevent inherited diseases. The Guardian, April 23 2015

Scientists develop technique that could stop a genetic disease being passed on to future generations. The Independent, April 23 2015

Links To Science

Reddy P, Ocampo A, Suzuki K, et al. Selective Elimination of Mitochondrial Mutations in the Germline by Genome Editing. Cell. Published online April 23 2015


 

 
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