Monday, 18 August 2014

Antibiotic resistance: Cameron warns of medical 'dark ages'

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Antibiotic resistance: Cameron warns of medical 'dark ages'

David Cameron: "We are in danger of going back to the dark ages of medicine"

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The world could soon be "cast back into the dark ages of medicine" unless action is taken to tackle the growing threat of resistance to antibiotics, Prime Minister David Cameron has said.
He has announced a review into why so few anti-microbial drugs have been introduced in recent years.
Economist Jim O'Neill will lead a panel including experts from science, finance, industry, and global health.
It will set out plans for encouraging the development of new antibiotics.
'Taking the lead'
The prime minister said: "If we fail to act, we are looking at an almost unthinkable scenario where antibiotics no longer work and we are cast back into the dark ages of medicine where treatable infections and injuries will kill once again."
Mr Cameron said he discussed the issue at a G7 leaders meeting in Brussels earlier this month and got specific support from US President Barack Obama and German Chancellor Angela Merkel.
It is hoped that the review panel's proposals will be discussed at next year's G7 summit, which will be hosted by Germany.
"Penicillin was a great British invention by Alexander Fleming back in 1928," Mr Cameron told the BBC. "It's good that Britain is taking the lead on this issue to solve what could otherwise be a really serious global health problem."
He said the panel would analyse three key issues: the increase in drug-resistant strains of bacteria, the "market failure" which has seen no new classes of antibiotics for more than 25 years, and the over-use of antibiotics globally.
'Time bomb'
It is estimated that drug-resistant strains of bacteria are responsible for 5,000 deaths a year in the UK and 25,000 deaths a year in Europe.
bacteriaA resistant strain of bacteria
Chief Medical Officer for England Prof Dame Sally Davies has been a key figure helping to get the issue on the government and global agenda.
Last year she described the threat of antimicrobial resistance as a "ticking time bomb" and said the dangers it posed should be ranked along with terrorism.
She spoke at a meeting of scientists at the Royal Society last month which warned that a response was needed akin to efforts to combat climate change.
Dame Sally said: "I am delighted to see the prime minister taking a global lead by commissioning this review.
"New antibiotics made by the biotech and pharmaceutical industry will be central to resolving this crisis which will impact on all areas of modern medicine."
Antibiotics dates of discovery timeline
Medical research charity the Wellcome Trust is providing £500,000 of funding for Mr O'Neill and his team, which will be based at their headquarters in central London.
Antimicrobial resistance has been a key issue for Jeremy Farrar, since he became director of the Wellcome Trust last year.
"Drug-resistant bacteria, viruses and parasites are driving a global health crisis," he said.
"It threatens not only our ability to treat deadly infections, but almost every aspect of modern medicine: from cancer treatment to Caesarean sections, therapies that save thousands of lives every day rely on antibiotics that could soon be lost."
'Market failure'
Antibiotics have been an incredible success story, but bacteria eventually develop resistance through mutation.
One example is MRSA, which has been a major threat for years in hospitals. It is resistant to all but the most powerful of antibiotics, and the main weapon against it is improved hygiene, which cuts the opportunity for infection to spread.
Without antibiotics a whole raft of surgical procedures would be imperilled, from hip replacements to cancer chemotherapy and organ transplants.
Before antibiotics, many women died after childbirth after developing a simple bacterial infection.
Mr O'Neill is a high-profile economist who is best-known for coining the terms Bric and Mint - acronyms to describe countries which are emerging and potential powerhouses of the world economy.
He is not, though an expert on antibiotics or microbes. But Mr Cameron told the BBC it was important to have an economist heading the review:
"There is a market failure; the pharmaceutical industry hasn't been developing new classes of antibiotics, so we need to create incentives."
Jeremy Farrar said: "This is not just a scientific and medical challenge, but an economic and social one too which would require analysis of regulatory systems and behavioural changes to solve them."
Mr O'Neill will begin work in September and is expected to deliver his recommendations next spring.
Last month antibiotic resistance was selected as the focus for the £10m Longitude Prize, set up to tackle a major challenge of our time.
Fergus Walsh, Medical correspondentArticle written by Fergus WalshFergus WalshMedical correspondent

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A nine-year-old boy who was born without ears has had a pair created from his ribs.

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Friday, 15 August 2014

Daily aspirin 'reduces cancer risk', study finds

Jack Cuzick has been reported here for his trials on aspirin.

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Taking aspirin every day could cut your risk of developing cancer, report BBC News and The Daily Telegraph among other news outlets, after the publication of a large-scale review of the evidence.
People aged between 50 and 65 who take aspirin every day for 10 years could cut their risk of bowel cancer by 30% and cancers of the throat and stomach by 25%, according to the study published in the Annals of Oncology.
Aspirin is an antiplatelet, which means it reduces the risk of clots forming in your blood. Platelets may also protect cancer cells in the body, and it has been suggested aspirin's effect on them may hinder this process. However, the exact mechanism is not well understood and more research is needed.
Taking aspirin every day comes with a serious health warning as it can cause serious side effects such as ulcers and bleeding from the stomach, particularly in elderly people.
However, the researchers argue the benefits of taking the drug need to be balanced against the harms. 
While the findings of this study show promise, it is not clear whether the methods used in compiling it were systematic, so the results may not be entirely reliable.
Anyone thinking of taking aspirin for prevention should talk to their GP first.

Who may not be able to take aspirin?

Before taking aspirin, including for pain relief, you should talk to your GP or pharmacist if:
  • you are pregnant, trying for a baby or breastfeeding
  • you have a blood disorder
  • you have ever had a stomach ulcer
  • you suffer from asthma
  • you have liver or kidney problems
  • you have high blood pressure
  • you have haemophilia or any other bleeding disorder
  • you have had an unusual or allergic-type reaction to any medicine
  • you are taking other medicines
Aspirin should also not be given to children under 16 years of age

Where did the story come from?

The study was carried out by researchers from a number of institutions across Europe and the US, including Queen Mary University of London.
It was funded by Cancer Research UK, the British Heart Foundation and the American Cancer Society. The study was published in the peer-reviewed medical journal Annals of Oncology.
Several of the study's authors are consultants to, or have other connections with, pharmaceutical companies with an interest in antiplatelet agents such as aspirin.
As might be expected with cancer-related news, the research was widely covered in the press. Most of the coverage was uncritical, although most stories warned of the side effects of taking aspirin.

What kind of research was this?

This was a review of evidence on the association between aspirin and incidence of deaths from cancer and cardiovascular disease, and potential harmful side effects.
It is not clear whether this was a systematic review, where the evidence is rigorously appraised for its quality and risk of bias. The researchers did not carry out a meta-analysis of the results of studies included, but compiled their own estimates.
The authors say regular aspirin is known to reduce the incidence of cardiovascular disease both in the general population and in high-risk groups, although it is currently only recommended for those at high risk.
However, an increasing body of evidence suggests it may also have a role in cancer prevention. Aspirin is also associated with a risk of bleeding and peptic ulcers. The researchers argue the benefits of taking the drug need to be balanced against the harms.

What did the research involve?

Researchers gathered evidence on the effects of aspirin on cancer risk and cancer deaths from systematic reviews published between 2009 and 2012, as well as from some individual studies on specific cancers. Further systematic reviews undertaken by some of the researchers were not included, but were discussed at the "evidence review meeting".
It is not clear how these studies were chosen or whether further studies on the topic were excluded and, if so, what criteria were used to decide which studies to include or exclude.
Evidence for aspirin's effect on cardiovascular disease was taken from one large meta-analysis. The authors based their calculations of the effect aspirin would have on cardiovascular disease by using UK rates from 1998 for cardiovascular-related incidents and deaths, which they adjusted to take account of downward trends in recent years in both the UK and the US.
The researchers used a detailed unpublished analysis of the harmful effects of aspirin.
They calculated the overall benefits and harms for taking aspirin for 10 years, starting at ages 50, 55, 60 and 65, separately for men and women. They made several assumptions in their analysis:
  • the cardiovascular benefit and adverse effects only occur during active treatment (the 10-year period)
  • the protection against cancer begins three years after initiating aspirin and continues for an additional five years after stopping aspirin
  • the protection against cancer mortality begins five years after starting aspirin use and lasts for an additional 10 years after treatment is stopped
  • the protective effects are seen only in colorectal, oesophageal, gastric, breast, prostate and lung cancers

What were the basic results?

The researchers calculated that for average-risk individuals aged 50 to 65 taking aspirin for 10 years, there would be a relative reduction of between 7% (women) and 9% (men) in the number of cancer, myocardial infarction or stroke events over a 15-year period, and an overall 4% relative reduction in all deaths over a 20-year period.
Below are their calculations of the effect of aspirin in reducing the risk of cancers and cardiovascular events, giving what the researchers say are "conservative" estimates:
  • colorectal (bowel) cancer – 30% reduction in incidence and 35% reduction in deaths
  • oesophageal cancer – 25% reduction in incidence and 45% reduction in deaths
  • gastric cancer – 25% reduction in incidence and 30% reduction in deaths
  • lung cancer – no reduction in incidence, 10% reduction in deaths
  • prostate cancer – 5% reduction in incidence, 10% reduction in deaths
  • breast cancer – 5% reduction in incidence, no reduction in deaths
  • heart attack – 18% reduction in incidence, 5% reduction in deaths
  • stroke – 5% reduction in incidence, 21% increase in deaths
Their calculations on the risk of side effects from taking aspirin are:
  • major (extracranial) bleeding – 70% increase in incidence
  • gastric bleeding – 70% increase in deaths
  • peptic ulcer – 70% increase in deaths
They also say the effects are not apparent until at least three years after starting aspirin, and some benefits may be sustained for several years after stopping.
They found no difference between low and high doses of aspirin in terms of health benefits, although there were no studies that did direct comparisons.

How did the researchers interpret the results?

The researchers say once aspirin's effect on cancer risk and mortality is taken into account, the benefits of taking aspirin outweigh the risks.
They calculate that to get any benefit, people need to start taking a daily dose of between 75mg and 325mg for a minimum of five years. Longer use is likely to have greater benefits, they say.
Further research is needed to determine the optimum dose for taking aspirin and duration of use, and to identify those at increased risk of bleeding.
In an accompanying press release, lead author Professor Jack Cuzick of Queen Mary University of London said: "It has long been known that aspirin – one of the cheapest and most common drugs on the market – can protect against certain types of cancer.
"But until our study, where we analysed all the available evidence, it was unclear whether the pros of taking aspirin outweighed the cons.
"Whilst there are some serious side effects that can't be ignored, taking aspirin daily looks to be the most important thing we can do to reduce cancer after stopping smoking and reducing obesity, and will probably be much easier to implement."


While the findings on aspirin and cancer show promise, it is not clear that the results are reliable from the methods reportedly used to compile this review.
This is because it included studies of varying design and quality, with much of the evidence coming from observational studies, which, while useful, cannot be totally relied on to test the effectiveness of healthcare interventions.
It's not clear how the studies included in the review were chosen and whether others on the same topic were excluded. It is also not clear whether or not this was a systematic review, where studies are rigorously appraised for their quality, and criteria are established for their inclusion.
Aspirin can cause major side effects such as peptic ulcers and bleeding from the stomach, particularly in older people. It's important to consult with your GP before deciding to take aspirin regularly. 

Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

Thursday, 24 July 2014

'More adults should be taking statins,' says NICE

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Reading the peer-reviewed literature on statins and other reports, I've suspected, for more than a year, that this advice (20mg/day Atorvastatin if QRISK2 10-year risk of CVD is 10% or more) would  be recommended by NICE.

"Doctors have been told to offer cholesterol-lowering statins to millions more people," BBC News reports.
New guidelines from the National Institute for Health and Care Excellence (NICE) recommend lowering the bar for statin use in adults at risk of heart disease. 
NICE suggests up to 8,000 lives could be saved every three years if everyone with a 10% risk of developing cardiovascular disease within the next 10 years is offered one of the widely used cholesterol-lowering medications.
Cardiovascular diseases are diseases affecting the heart and blood vessels, such as heart disease and stroke.
NICE says the evidence clearly shows statins are safe and effective and would be a good use of healthcare resources if given to these people.
The announcement has been met with a variable response, with the Daily Mail saying up to half of all adults could now be eligible for the drugs, and that, "GPs warn of chaos" at being "told to trawl medical records to find at-risk patients".
On the other side of the argument, Professor Baker, director of the Centre for Clinical Practice at NICE, says the new recommendations would not create an additional workload for GPs.
On the NICE website, he said: "Most patients will already be under surveillance by their GPs, so this won't add any additional workload. But you can do the QRISK2 risk assessment yourself. It can be done online or via an app, so it doesn't need to be done by the GP."
You can assess your own risk online using a risk assessment tool based on factors such as smoking history, body mass index (BMI) and family history of heart disease.
The NICE guidelines have now been published, which means they will come into effect in the NHS in England. However, NICE still recommends preventable lifestyle measures, such as losing weight or stopping smoking, are addressed first before starting statin treatment.
Ultimately, the decision to take a statin – even if it is recommended – will always remain a choice that sits with the patient.

Statins and reporting bias

Visit any medical news forum or comment board, such as the Mail Online's health section, and search for statins, and you will see stories of statins causing terrible side effects – for example, how statins left a person "crippled with pain and brain fog".

While the issue of side effects should never be ignored, the bad press statins get online could be an example of reporting bias in action – where there is selective reporting (or suppression) of information.

In other words, people who tolerated statins poorly are more likely to report that fact than people who have been taking them for years with no adverse effects. Similarly, most UK newspapers are unlikely to run an "I took statins, I had no side effects, and they probably prevented a heart attack" story. Good news rarely shifts newspapers or gets clicks on websites.

What are statins?

Statins are usually the first medication of choice to reduce the levels of low-density lipoprotein (LDL, or "bad")cholesterol in the blood.
Cholesterol and other fatty substances can build up and clog the arteries in the heart and elsewhere in the body, leading to cardiovascular diseases. Reducing cholesterol levels helps reduce the risk of cardiovascular events such as heart attack or stroke.
Examples of statin drugs aresimvastatin and atorvastatin, which come as tablets. The recommended treatment course is to usually take a tablet once a day for life.

What is NICE recommending?

NICE has published an update to its previous clinical guideline on the cardiovascular risk assessment and management of lipids (fats in the blood, which includes cholesterol and triglycerides) in people who either already have cardiovascular disease (such as those who've had a heart attack or stroke), or people who are at risk of developing cardiovascular disease.
The main new recommendations are that:
  • A systematic strategy should be used in general practice to identify people who are likely to be at high risk for developing cardiovascular disease (CVD).
  • People should be prioritised for a full risk assessment if their estimated 10-year risk of CVD is 10% or more (using the QRISK2 assessment tool).
  • Before starting lipid-lowering medications for the prevention of CVD, at least one blood sample should be taken to measure total cholesterol, high-density lipoprotein (HDL, or "good") cholesterol, non-HDL cholesterol, and triglyceride concentrations.
  • In people who have a 10% or greater risk of developing CVD within the next 10 years, the recommended statin to start treatment with is atorvastatin, given at a dose of 20mg daily.
  • In people who already have established CVD (people who have heart disease or have had a stroke), the recommended starting dose of atorvastatin is 80mg daily (unless there are side effects or other contraindications).
For people at risk of developing CVD within the next 10 years, the recommendations to start 20mg atorvastatin applies to adults of all ages, including people over the age of 85 years (in very elderly people, statins may reduce the risk of a non-fatal heart attack). This advice stands unless there are other health-related factors that make statin treatment inappropriate.
NICE does make several important provisions around decisions to start treatment for the prevention of CVD in people considered to be at risk.
These are outlined below.

Patient-doctor discussion

The decision whether to start a statin should be made after an informed discussion between the doctor and patient about the risks and benefits of treatment, taking into account factors such as:
  • possible benefits from lifestyle modifications (measures that could be tried first before starting a statin, such as exercising more, eating a healthier diet and stopping smoking)
  • patient preference
  • other medical illnesses
  • the problems of adding another tablet if the person is already taking a lot of daily medications
  • general frailty and life expectancy

Lifestyle changes

Before starting statin treatment, assessment should be made into other health and lifestyle factors that may need management, including:
  • smoking and alcohol consumption
  • blood pressure
  • BMI
  • diabetes
  • kidney or liver disease
The benefits of optimising all other modifiable lifestyle risk factors (for example, overweight/obesity or smoking) should be discussed, and people offered support for this if needed, such as exercise referral programmes.
Statin treatment may then be considered if lifestyle modifications don't work.

What is the rationale for lowering the threshold for the drugs?

Currently, one-third of deaths in the UK are caused by cardiovascular disease, accounting for around 180,000 deaths each year.
Cardiovascular disease is well known to have a significant burden of disability. It is believed £8 billion of healthcare resources are tied up in the disease.
Professor Mark Baker, director of the Centre for Clinical Practice at NICE, says: "Doctors have been giving statins to 'well people' since NICE first produced guidance on this in 2006. We are now recommending the threshold is reduced further.
"The overwhelming body of evidence supports their use, even in people at low risk of CVD. The effectiveness of these medicines is now well proven and their cost has fallen. The weight of evidence clearly shows statins are safe and cost effective for use in people with a 10% risk of CVD over 10 years."
Dr Anthony Wierzbicki, from Guy's and St Thomas' Hospitals, London, and chair of the Guideline Development Group, also commented on the new guidance: "We've been able to simplify the guideline so it's now much easier for patients to be assessed and for GPs and nurses to make sense of the results. There is greater clarity, a simpler framework, and a systematic way of identifying people who could benefit from treatment.
"We've got the best evidence base, huge numbers, and the biggest set of clinical trials ever done. Other areas of medicine would give their teeth for this evidence, it's that good. Statins work, they are very cheap, and are becoming considerably cheaper as they come off-patent, which, in a cost-limited health service, is a big consideration.
"That enables us to actually say that we should treat people with heart disease a lot more intensively because we know that will prevent further events. In people with diabetes or kidney disease, giving a statin will reduce heart attacks and strokes. For people at risk of heart disease, if lifestyle measures fail, we have a second option of giving them a statin if they want and require it."

Are there any risks or side effects with statins?

Statins are fairly safe drugs, though there are a range of possible side effects and groups of people who should use them with caution. This includes people with an underactive thyroid, kidney disease and liver disease. Women should also not take statins while pregnant or breastfeeding.
Possible side effects include headaches and dizziness, sleep disturbances, fatigue, tummy disturbances, altered sensation, and sensitivity reactions such as rash or itching.
Very rarely, statins have been associated with the risk of having a toxic effect on the muscles, causing muscle pain and weakness, and even a serious condition called rhabdomyolysis, where the muscle fibres start to break down.
However, the risks and benefits would be discussed and taken into account for any individual before a statin is prescribed, including their personal and family medical history.

How has the announcement been received by the media?

As the BBC News headline indicates, NICE's decision has been met with controversy. 
Professor Mark Baker, the director of the Centre for Clinical Practice at NICE is quoted as saying: "Prevention is better than cure. One of the mainstays of modern medicine is to use treatments to prevent bad things happening in the future. It's why we use vaccines and immunisation to prevent infectious disease, it's why we use drugs to lower blood pressure to prevent heart attacks, strokes, and kidney disease, and it's why we're using statins now."
Meanwhile, in opposing camps there is debate about "medicalising" a nation and encouraging people to just pop a pill rather than following a healthy lifestyle.
The British Medical Association's General Practitioner Committee is quoted as saying: "There is insufficient evidence of significant overall benefit to low-risk individuals to allow GPs to have confidence in the recommendation. The measure would distort health spending priorities and disadvantage other patients."
However, as quoted in the Daily Mail, Professor Baker responded: "It is ludicrous to suggest that we are overmedicalising the population when the whole point of using modern, safe and effective drugs in an economic way is to prevent bad things happening in the future."
Dr Chaand Nagpaul, chair of the British Medical Association's GP committee, feels NICE has not taken into account the additional pressures they'll be placing on GPs. "In making their decision, NICE has failed to take the current pressures on general practice into account, and the further impact this will have on already overstretched GPs and those patients requiring treatment for other illnesses."
Despite the extensive debate and opposition, as BBC News also highlights, the 10% threshold for statin treatment is comparable to that already used in other European countries.
As the president of the Academy of Medical Sciences, Professor Sir John Tooke, points out on the BBC News website: "Whether or not someone takes drugs to diminish their risk is a matter of personal choice, but it must be informed by accurate information on the balance of risk and benefit in their particular case. The weight of evidence suggests statins are effective, affordable and have an acceptable risk-benefit profile."


Despite somewhat hysterical media coverage to the contrary ("millions more to be given statins," according to the Daily Express), nobody will be forced to take statins.
If your GP does recommend statins, you should ask them to explain the benefits and risks for you personally of starting statin treatment. You may want to find out more about statins before making up your mind – the NHS Choices Health A-Z information on statins is a good place to start.
If you do experience troublesome side effects while taking statins, contact your GP or the doctor in charge of your care. It could be the case that adjusting your dosage or switching to a different type of statin could help relieve any side effects.
Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

Wednesday, 16 July 2014

Prediabetes label unhelpful, experts argue

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“Pre-diabetes label ‘worthless’, researchers claim,” reports the BBC.
The headline is based on an opinion piece published in the British Medical Journal (BMJ) by John Yudkin and Victor Montori, both of whom are professors of medicine.
They argue that diagnosing people with “prediabetes” puts people at risk of unnecessary medicalisation and creates an unsustainable burden on healthcare systems.
The piece is part of an ongoing BMJ series called “Too much medicine”, which is examining what is known as over-medicalising  treating “problems” that don’t actually require treatment.
They argue that money would be better spent changing food, education, health and economic policies.
This is an opinion piece. Although the authors support their opinions with studies, other evidence available could contradict their views.

Not that one

One of the authors, John Yudkin, should not be confused with the nutritionist and anti-sugar campaigner of the same name – not least, because the latter died in 1995.

What is meant by ‘prediabetes’?

Prediabetes is used to describe people at risk of diabetes because they have impaired glucose metabolism, but who do not meet the criteria for diabetes and often have no noticeable symptoms.
It is a term that was introduced by the American Diabetes Association (ADA), but has not been accepted by other health organisations, such as the World Health Organization (WHO).
It may be defined as:
  • impaired glucose tolerance
  • above normal glucose blood concentration after fasting
  • above normal glycated haemoglobin (a marker of average blood glucose concentration)
Supporters of the term’s usage argue that it allows doctors to identify high-risk patients, so they can be treated in order to prevent diabetes from occurring.

What objections do the authors have about the use of the term?

The authors point out that there has been little support for the ADA’s prediabetes label from other expert groups, including WHO, the International Diabetes Federation and the UK’s National Institute for Health and Care Excellence (NICE).
The authors say this is because the ADA has lowered the thresholds for impaired fasting glucose and glycated haemoglobin. Because it encompasses all three aspects of impaired glucose metabolism (impaired glucose tolerance, above normal fasting blood glucose, above normal glycated haemoglobin), the lowered thresholds have created a large, poorly characterised and heterogeneous (mixed) category of glucose intolerance.
In other words, the diagnostic criteria are now so broad (in the opinion of the authors) that it is, essentially, useless.
The authors say that using the ADA’s definition of prediabetes would result in two to three times as many people being diagnosed with impaired glucose metabolism. This would lead to 50% of Chinese adults being diagnosed with prediabetes – over half a billion people.
The authors also question the value of diagnosing people with prediabetes.
They point out that the drugs used to treat people with prediabetes in order to stop them developing diabetes are often the same as the drugs they would take if they actually developed diabetes.
The side effects of these drugs must be measured against the fact that many people with prediabetes, who remain untreated, will not go on to develop the condition.
They also discuss the merits of lifestyle interventions, such as regular exercise and improved diet.
They point out that these types of interventions are of use for all adults, so they question the wisdom of only promoting these interventions to specific groups. A better use of campaigning would be to target all adults, they say.

What dangers or risks do they claim could occur by using the term?

The authors suggest that a label of prediabetes, while not causing any physical symptoms, could still cause:
  • problems with self-image
  • anxiety about future complications
  • challenges with insurance and employment
  • a need for medical care and treatment
  • increased healthcare costs
  • medication side effects, if prediabetes is treated with drugs
In their opinion, the diagnosis would cause more problems than it solves.

What do the researchers suggest instead?

The researchers say that the risk factors for developing a whole host of chronic diseases overlap, and that money would be better spent changing food, education, health and economic policies.

What should I do if I have been told I have prediabetes or that I am at high risk of developing diabetes?

If you have been told you have prediabetes, or that you have a high risk of developing diabetes, you can reduce your risk of developing the illness by:
Read more advice about lowering your diabetes risk.
Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

Links to the headlines

Links to the science

Yudkin JS, Montori VM. The epidemic of pre-diabetes: the medicine and the politics. BMJ. Published online July 15 2014

Wednesday, 11 June 2014

Cannabis can damage lives, researchers argue

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Monday June 9 2014
“Smoking marijuana as a teenager lowers IQ for life, scientists warn,” the Mail Online reports. The headline is prompted by a critical review looking at the evidence about the potential harms associated with cannabis use.
This latest review was written by researchers from the US National Institute on Drug Abuse and provides an overview of the potential harms associated with cannabis use, ranging from increased risk of car accidents to an adverse effect on “life achievement”.
The Mail’s coverage of the story was an accurate representation of the research, although it took the review findings at face value and did not mention any of its limitations. The most important of which is that it does not appear to be a systematic review, where all available evidence on a particular topic is assessed.
It is unclear whether this study was prone to “cherry picking” – where evidence that supports the researchers’ arguments is included while evidence that opposes it is ignored. This has the potential to bias the findings and conclusions.
The timing of the study is also interesting. After the quasi-legalisation of cannabis in the states of Colorado and Washington there have been increasing calls to roll-out similar laws across America.
Many of the review's conclusions were tentative or indicated more research was needed. Based on this review alone, research into the effects of cannabis use in humans has not yet yielded any firm conclusions and often paints an unclear or inconsistent picture.

Is cannabis safe?

No. Cannabis has been linked to both mental health conditions such asschizophrenia and physical conditions such as chronic bronchitis and lung cancer

Read more on the potential harms of cannabis.

Pro-legalisation advocates argue that it is a much safer drug than cigarettes and alcohol in terms of damage to the person and wider society through crime and disorder. And while that may appear to be the case, we have far less evidence on the effects of cannabis than we do on the effects of alcohol and tobacco.

What is the basis for these current news reports about cannabis?

The authors state cannabis (marijuana) is the most commonly used illicit drug in the US with around 12% of people over the age of 12 reporting use in the past year, with particularly high rates among young people.
The regular use of cannabis in adolescence was of particular concern to the review group because of a higher chance of potential harm in younger groups.
The review highlighted a popular belief of cannabis as a harmless vice. Given the loosening of laws and regulation on recreational use in in some US states (Colorado and Washington), some may see this as giving legitimacy to this idea. And in response to the increase in the legalisation of cannabis for medical and recreational use in the US, patients may be more likely to ask their doctors about its potential benefits and risks to health.
The authors indicated many scientific studies report harmful effects associated with cannabis but others do not, which has led to heated debate about whether cannabis is harmful.
The review aimed to assess the current state of the science on the adverse health effects of recreational cannabis use, focusing on those areas for which the evidence is strongest.

What did the report find?

The review was broad, covering addiction, neurodevelopment, mental illness, risk of cancer and life chances.

Risk of addiction

The authors indicated that, “despite some contentious discussions regarding the addictiveness of marijuana, the evidence clearly indicates that long-term marijuana use can lead to addiction”. Around 9% of those who experiment with cannabis become addicted, and this figure rises to 50% of those who smoke it every day, the review said.

Effect on brain development and IQ

The negative effects of cannabis use on the brain were said to be particularly prominent if use starts in adolescence or young adulthood. The review flagged up one study that found an association between frequent use of cannabis from adolescence into adulthood with significant declines in IQ.

Role as a gateway drug

There is a theory that using cannabis in early adulthood could encourage the use of other addictive drugs such as nicotine or alcohol. The review found animal studies that were consistent with this theory. However, they also acknowledged they didn’t know whether people with more addictive tendencies are more likely to try cannabis, alcohol and nicotine, or whether cannabis use itself directly increased the chances of them trying these things.

Mental illness

Regular cannabis use was reported to be associated with an increased risk of anxiety and depression, but causality has not been established.
It has also been linked to psychosis (including those associated with schizophrenia), especially among people with a pre-existing genetic vulnerability, and worsens illness in people with schizophrenia.
The authors say it is difficult to establish causality in these types of studies, because factors other than cannabis use may be directly associated with the risk of mental illness. Other factors could also predispose a person to both cannabis use and mental illness. This makes it difficult to confidently attribute the increased risk of mental illness to cannabis use.

Effect on school performance and lifetime achievement

The review indicated that cannabis use impairs critical cognitive functions, both during acute intoxication and for days after use. For this reason, students who smoke cannabis could be functioning at a cognitive level that is below their natural capability for considerable periods of time. However, the results from studies included in the review were inconsistent.
Some studies suggested the long term negative effects of cannabis use on learning may be reversible, whereas others indicated memory and attention got significantly worse the more years someone had been using cannabis regularly.
Some studies suggested early cannabis use is associated with impaired school performance and an increased risk of dropping out of school, but there were other factors that could explain this link. For example, shared environmental factors like growing up in a neighbourhood where drug use is high and academic achievement low.

Risk of motor-vehicle accidents

There were studies indicating that both immediate exposure and long-term exposure to cannabis impair driving ability. According to a meta-analysis, the overall risk of involvement in an accident increases by a factor of about two when a person drives soon after using cannabis. The risk associated with the use of alcohol in combination with cannabis was reported to be greater than that associated with the use of either drug alone.

Risk of lung cancer

The effects of long-term cannabis smoking on the risk of lung cancer are unclear and often complicated by the fact many cannabis smokers also smoke tobacco – which is known to cause cancer. Separating the health effects of the two types of smoking remains a challenge. The researchers warned that the strength of cannabis in circulation is increasing and so any potential risks may also be increasing.

Can we believe the review’s findings?

The review’s main weakness is that it didn’t describe how it searched and reviewed the evidence on this subject and whether this was systematic. This means that key evidence may have been missed, leading the authors to potentially draw biased conclusions. It is not possible to say that the results were biased; only that without the methods, there remains a risk that they are.
A second limitation is that the evidence behind the review’s conclusions was drawn largely from early animal studies, or from observational studies that couldn’t establish cause and effect. This means we can’t really make clear cut, definitive statements about the health effects of cannabis use as the evidence, at least the evidence identified in this review, was not strong in most areas. The long term effects of cannabis use, for example, remain in the authors’ words “poorly understood”.
The review generally highlighted a scarcity or lack of knowledge on the beneficial or harmful effects of cannabis. This may be a true reflection of the evidence base, or may be in part because the review has not included all the relevant evidence.
One of the biggest challenges in studying the effects of cannabis is that due to its legal status in much of the world, researchers could not legally use cannabis in the “gold standard” of studies – a randomised controlled trial. There could also be ethical problems in randomly assigning people to use cannabis who don’t already, given its potentially damaging effects.
As more and more parts of the world are now legalising (or at least partially decriminalising) cannabis, research of this type could potentially be carried out and may allow us to learn more about the benefits and risks of this widely used drug.
Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

Links to the headlines

Links to the science

Volkow ND, Baler RD, Compton WM, Weiss SRB. Adverse Health Effects of Marijuana Use. The New England Journal of Medicine. Published online June 5 2014