Last updated April 8, 2019 at 10:04 am
Heart disease is one of the most common causes of death in people with anorexia. One Aussie researcher is examining the nervous system to work out why.
A two-year research project at Swinburne is investigating the physiology of anorexia nervosa with the aim of reducing the alarmingly high number of heart disease deaths caused by the condition.
As many as 30,000 people in Australia suffer from anorexia nervosa, and about 6% of these die as a consequence of the disease, the highest mortality rate of any psychiatric disorder. Globally, suicide accounts for up to 20% of anorexia deaths, considered the leading cause of mortality. As a result, treatment is often primarily psychologically based. But an additional 5% of deaths are due to sudden cardiovascular complications, while a further unknown number die later of cardiovascular disease.
Anorexia is characterised by excessive dieting, purging and, often, over-exercising. “Of course, this starvation places a lot of stress on the body,” explains Associate Professor Elisabeth Lambert, who is heading up the study through Swinburne’s Iverson Health Innovation Research Institute. “Ultimately, the disease can affect every organ system and so potentially can result in many very serious medical complications.” These can have immediate impacts on the heart, but also long-term cumulative effects on cardiac health that compound with time.
Lambert hopes to catch those most at risk of this by identifying a particular set of predictive markers. “We want to see if there are disturbances in the function of the nerves of the autonomic nervous system and if this is the cause of the dysfunction of the heart and metabolic abnormalities associated with anorexia.”
Lambert’s professional expertise is in the areas of neurophysiology and cardiology. She joined Swinburne in 2017 after almost 20 years with the Melbourne-based Baker Heart and Diabetes Institute, with whom she still has strong links. She brings to Swinburne highly specialised experience in a technique known as microneurography.
The slightly invasive technique requires an electrode to be inserted directly into the peroneal nerve behind the knee in test subjects. This allows researchers to measure electrical impulses in the nerves of the autonomic nervous system (ANS), which regulates body functions that we’re not conscious of controlling, such as the maintenance of our blood pressure or breathing rate. It is also the only direct way to measure the activity of the sympathetic nervous system (SNS) – the part of the ANS that controls many of our body’s base functions and activates the neuronal and hormonal stress reaction to risk known as the ‘fight-or-flight’ response.
Microneurography readings, says Lambert, offer a way of examining the body’s activity at rest and in response to physiological stressors on the heart, such as hypertension, obesity and, of course, anorexia. That in turn, she says, offers the opportunity to identify the mechanisms responsible for aberrant nerve behaviour and can direct therapy in order to reverse or prevent associated problems.
There are only three groups in Australia proficient in microneurography, and Lambert’s capabilities in the area, built up during two decades, are considered to be world-leading. She’s not only able to work out the rate at which nerves fire in response to certain stressors, but also identify tell-tale firing patterns in obese and lean people.
Lambert learned to spot these markers while exploring how SNS regulation can underpin the development and maintenance of cardiovascular disease risk in obese individuals. This work had shown an elevated level of activity of nerves in the SNS of overweight, but otherwise healthy, young adults. This in turn was associated with subtle damage to the kidneys and heart.
Anorexia metabolic changes resemble being overweight
The link for Lambert is that people with anorexia develop metabolic abnormalities that resemble that of overweight people. This includes the way lipids show up in blood tests, she says. At first, it may sound counterintuitive to think there are similarities between the impact of overeating and undereating. “But the thing is that eating too much or not eating too much may put pressure on the body and impact similarly on, for instance, kidney or heart function,” says Lambert.
“Now we want to investigate individuals with anorexia because we think that they may present with similar problems associated with sympathetic nervous activation.”
Lambert even thinks she may be able to tinker with nerve activity directly through the use of drugs, exercise and diet. “Our current investigations explore several ways of altering SNS activity in obese individuals,” she says. “The aim is to reveal whether these approaches could be beneficial in reversing or slowing down the progression of cardiometabolic disease.”
Like most Swinburne projects, Lambert’s project is highly collaborative with specialist clinical groups outside the university. She is working to recruit test subjects with the Melbourne Clinic’s Eating Disorder Unit and psychiatric department of St Vincent’s Hospital, Melbourne.
“We will look at patients who used to have anorexia, who are currently well but went through that strain and stress [of the disease] and we will try to see if we can pick up some abnormalities in the heart and so on.” The study will also be recruiting people presently in an acute stage of anorexia to see if they can map differences at that point as well.
Hub of anorexia and body image research
Lambert’s work in anorexia builds on a broader program investigating the disorder within Swinburne’s Centre for Mental Health, which is headed by neuropsychologist Professor Susan Rossell.
“The centre has a large anorexia and body image program, and this particular [microneurography] project adds a new dimension to it,” explains Professor Gavin Lambert, Director of Swinburne’s Iverson Health Innovation Research Institute.
Bringing microneurography into the centre’s capabilities also potentially adds a powerful dimension to other areas at Swinburne. “It’s relevant for high blood pressure, heart failure, diabetes,” he says. “It could be relevant for people with panic disorder and people with depression.”
By combining this capability with Swinburne’s already formidable multimillion dollar Neuroimaging Facility and expertise within the Centre for Mental Health, it should be possible to determine the brain regions that are actually governing the firing rate of particular nerves. That means being able to determine the pathways in the brain involved in generating sympathetic nerve activity. And that, of course, could set researchers on the path to finding treatments for the physical impacts of not just anorexia, but many other disorders involving the sympathetic nervous system.
Help is available for eating disorders. Contact the Eating Disorders Helpline on 1300 550 236.