A potentially alarming figure that emerged in the UK news last week was that “1 million” UK adults may have been wrongly diagnosed with asthma – a claim reported in various forms by BBC News, The Guardian, The Daily Telegraph, the Daily Mirror and the Mail Online. 

The headlines followed the publication of new draft guideline (PDF, 670kb) from the National Institute for Health and Care Excellence (NICE) on the diagnosis and management of asthma. Most of the media articles were true to the facts and explained that the guideline was aiming to improve asthma care by improving the accuracy of diagnosis.

So, where did the figure of 1 million come from? All the UK press rallied round a statement in the draft guideline that said: “studies of adults diagnosed with asthma suggest that up to 30% do not have clear evidence of asthma”. What followed was clearly a “back of the envelope” calculation extrapolating this to the number of people receiving treatment for asthma in the UK, which is around 4.1 million. This gave the magic figure of 1.23 million potentially misdiagnosed people.

Unfortunately, the 30% figure in the draft guideline is not referenced, so we can’t find out how accurate it is. We also don’t know whether it applies to specific asthma subgroups, such as those of a specific age, or the severity of a person's symptoms. This makes it difficult to assess whether this calculation is accurate, or even reasonable.

The charity Asthma UK responded in a blog post, saying: “While we welcome the NICE guideline in the hope that it will help people with asthma to receive more personalised care, we are concerned that today’s headlines may make people think twice about taking their asthma medicines”.

“Although it is true that some people may receive treatment for asthma when they currently don’t have symptoms, this does not necessarily mean that they don’t have asthma. So it is vital that everyone diagnosed with asthma keeps taking their medication as prescribed and attends their annual asthma review”.

You should never stop taking any prescribed medication without first consulting with your GP or the doctor in charge of your care. This includes asthma medication.

What is the basis for these current reports?

NICE recently released a draft guideline to improve asthma diagnosis and monitoring.

The draft guideline – NICE's first on asthma – is now open for consultation until March 11 2015, so people and institutions can comment on its initial recommendations. The feedback and comments will be collated and incorporated into revised recommendations. Once agreed, these will form official NICE guidelines, which are expected to guide standard healthcare practice across the UK.

The draft guideline covers the diagnosis and monitoring of asthma in adults, children and young people. It draws on the best evidence available to determine the most clinical and cost-effective way to diagnose people with asthma and determine the most effective monitoring strategy to ensure optimum asthma control.

What does it say?

The draft guideline outlines that there is currently no gold standard test available to diagnose asthma. At the moment, it is mainly based on a thorough history of symptoms taken by an experienced clinician.

However, the guideline stresses that to achieve a more accurate diagnosis, clinical tests should be used alongside symptom assessment. The process the healthcare professional should follow in the initial assessment, and the tests to use, are presented in simple flow charts.

This involves using a combination of tests, depending on the age of the person being assessed. Most commonly this will involve a test called spirometry, to test lung function. This will sometimes be repeated after a person has been given inhaled treatment to dilate the airways – known as a bronchodilator reversibility test. Other tests that may be used include measuring fractional exhaled nitric oxide, as a sign of airway inflammation, and looking at whether the airways are over-responsive to inhaled substances, such as histamine or methacholine. 

The guidance also says that around one in 10 adults with asthma develop the condition because they are exposed to certain substances, such as chemicals or dust, in their workplace. Therefore, the draft guideline now recommends that healthcare professionals ask employed people how their symptoms are affected by work, to check if they may have occupational asthma.

How does the guideline affect you?

If you have asthma, do not change your medication without first consulting a doctor. This could be dangerous, as untreated asthma can be fatal.

If you have concerns that you have been misdiagnosed or are taking medicines unnecessarily, the first thing to do is speak with your health professional.

At present, these guidelines are in a draft form, so may be revised based on feedback and comment over the next few months. In the meantime, there aren’t likely to be changes in the way asthma is diagnosed routinely across the NHS. However, if the changes proposed in this draft make it into the final version, this may lead to a change in practice – most likely, more standardisation around the diagnosis and monitoring of asthma.

The main implications of such a change would be that the accuracy of diagnosing new asthma cases should improve or standardise for people in the UK. The implications for people already diagnosed with asthma are less clear. It could potentially mean that cases where there was uncertainty around the diagnosis would be re-reviewed with further diagnostic tests. This could potentially lead them to be declared asthma-free, or to a change in their medications, as appropriate.

This is a good reminder to take full advantage of your asthma review, which is an appointment with your doctor or asthma nurse to talk about your asthma and discuss how you can better control your symptoms. This is something that everyone with asthma should do at least once a year or more if you have severe asthma symptoms.

NICE says it wants to hear your views. Information on how to comment on the draft guideline can be found here.

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

Links To The Headlines

Asthma diagnosis 'may be wrong' in one million UK adults. BBC News, January 28 2015

More than 1m people in UK may have been wrongly diagnosed with asthma. The Guardian, January 28 2015

More than 1m people with asthma may NOT have the condition and could be taking medication unnecessarily. Mail Online, January 28 2015

One million asthma sufferers may not have the condition, warns health watchdog. The Daily Telegraph, January 28 2015

Asthma: More than 1 MILLION people may have been wrongly diagnosed with the incurable condition. Daily Mirror, January 28 2015

More than 1m asthma sufferers may have been misdiagnosed. Daily Express, January 28 2015

"Three glasses of milk every day ‘helps prevent Alzheimer's and Parkinson's’," is the misleading headline in The Daily Telegraph. The study it reports on only found that a high-dairy diet was linked to increased levels of an antioxidant called glutathione.

It is also unclear what, if any, protective effects higher levels of glutathione would have against Alzheimer’s or Parkinson’s disease.

The study, funded by the US Dairy Research Institute, looked at brain MRI scans of 60 adults aged between 60 and 85 using a new technique that could measure levels of glutathione.

This antioxidant is said to "neutralise" potentially harmful chemicals in the brain. Lower levels are found in conditions such as Parkinson’s disease and Alzheimer’s disease, but it is not known whether this is part of the cause of the conditions or a consequence of them.

The level of glutathione was determined once, at the same time as participants were asked about their diets. This study therefore cannot tell us that a high-dairy diet caused the increased levels of glutathione. It is also unable to show what happens to glutathione levels over time or whether the higher levels are protective.

So, all in all, this study proves little. Dairy products are important for bone health and are recommended in moderation as part of a healthy diet, but we just don’t know if they are good for the brain.

Where did the story come from?

The study was carried out by researchers from the University of Kansas Medical Center. It was funded by the US Dairy Research Institute, with further funding provided by the National Institute for Health and the Hoglund Family Foundation. The funding organisations did not have a role in study design, implementation, analysis, or interpretation of data.

The study was published in the peer-reviewed American Journal of Clinical Nutrition.

The Daily Telegraph’s reporting on the story was poor and its headline was inaccurate. It says that people "who guzzled the white stuff were more likely to have healthy brains", when in fact all of the people in the study were healthy. It is also not known whether increased levels of glutathione prevent neurodegenerative disorders, so we can’t say that people with higher levels definitely have "healthier" brains.

The Mail Online’s coverage was slightly more restrained, opting to say that it "may help protect" rather than "will help protect".

What kind of research was this?

This was a cross-sectional study, which measured the level of glutathione in the brain using a new MRI scanning technique. Glutathione is an antioxidant which helps prevent damage to cells. Reduced levels of glutathione have been found in the early stages of Parkinson’s disease, though it is unclear if this might contribute to the development of Parkinson’s or is the result of Parkinson’s.

The researchers wanted to see if drinking milk was associated with higher levels of glutathione in the brain. As it was a cross-sectional study, it only measured the level of glutathione at one time point, and did not follow people up over time to find out what happened to them. This means it was not able to show whether dietary consumption might directly affect glutathione levels in the brain, or indeed whether higher levels were protective against brain diseases such as Parkinson’s disease or Alzheimer’s.

What did the research involve?

The researchers recruited 60 healthy older adults, assessed their dairy intake and measured their level of glutathione in the brain using an MRI scan. They then analysed whether increased consumption of milk was associated with higher levels of glutathione.

The participants were adults aged between 60 and 85, who were healthy and did not have a history of:

• neurologic (brain and nervous system) disorders
• head injury
• claustrophobia (which would make them unsuitable for MRI scanning, as getting a scan involves lying in a small metal tube)
• diabetes
• unstable medical conditions
• lactose or gluten intolerance
• taking glutathione or N-acetylcysteine supplements

The participants completed three 24-hour food frequency questionnaires by telephone with a dietician, and a seven-day diet record was filled in before the MRI scan. From these assessments, the researchers categorised the participants into the following three groups, according to their daily consumption of dairy products:

• low dairy intake, less than one serving per day
• moderate dairy intake, one to two servings per day
• "recommended" dairy intake, three or more servings per day (this was based on US recommendations)

They also had other measurements taken, including body mass index (BMI), waist circumference and body composition of fat and muscle. Finally, they had a brain MRI scan using a new process (known as chemical shift imaging) that had been developed by the researchers to measure the level of glutathione.

The results were then analysed to see if increased dairy consumption was associated with higher levels of glutathione.

What were the basic results?

The participants’ characteristics were similar across the three groups in terms of age, BMI, educational level and quality of their diet.

Glutathione levels in the front and sides (parietal region) of the brain were higher in people who consumed more dairy products, milk and calcium.

The study did not assess whether this difference would affect a person’s health in any way, or how levels fluctuate over time.

How did the researchers interpret the results?

The researchers concluded that "glutathione concentrations were significantly related to adults’ reported consumption of dairy foods and calcium". They say that further research is required to see if increased levels of glutathione prove to be effective in "strengthening cerebral antioxidant defenses [sic] and, thereby, improving brain health in the aging population".

Conclusion

This small study found people with higher dairy, milk and calcium consumption had higher levels of glutathione in the frontal and parietal regions of the brain. Glutathione is an antioxidant that helps to "neutralise" potentially harmful chemicals in the brain.

Research into glutathione and its role in neurodegenerative diseases is in the early stages. It is known that the levels reduce with age and in certain conditions such as Alzheimer’s disease and Parkinson’s disease, but it is not known whether this is part of what leads to the disease or a consequence of the disease. This study does not show whether increasing the level of glutathione would protect against these types of conditions.

This study was cross-sectional, so measured the level of glutathione at one time point in older adults who were healthy. It therefore does not answer the question of whether people with more glutathione in their brains are less likely to develop neurodegenerative disorders.

In addition, previous research has found that in Parkinson’s disease, glutathione levels are only reduced in an area of the brain called the substantia nigra, which is located in the middle of the brain. This study did not look at levels in this part of the brain.

This was a relatively small study, which found a relatively wide range of glutathione levels ranged in different areas of the brain. A much larger study would be required to understand what the normal range is in the population, and how this differs in various disease states. The study is also reliant on self-reporting of dietary intake which can be inaccurate. There is also little information about other factors which could influence the results such as socioeconomic status, ethnicity, family history of Alzheimer’s disease or Parkinson’s disease, other conditions or medication use.

In conclusion, this study has found that increased reported consumption of dairy and milk products was associated with increased levels of the antioxidant glutathione in the brain, but it cannot prove that this was due to the diet or that this will prevent brain disease.

Larger studies into the role of both dairy products and glutathione on neurodegenerative diseases would be useful.

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

Links To The Headlines

Three glasses of milk every day 'helps prevent Alzheimer's and Parkinson's'. The Daily Telegraph, March 25 2015

Three glasses of milk a day 'to beat dementia': People who drink large amounts of the white stuff have higher levels of antioxidant that helps protects brain cells. Mail Online, March 26 2015

Links To Science

Choi I, Lee P, Denney DR, et al. Dairy intake is associated with brain glutathione concentration in older adults. The American Journal of Clinical Nutrition. Published online December 10 2014