Posts filed under Medical news (341)

I’ve been away or busy for a couple of weeks, so here are some collected links on statistics, graphics, the media, and risk

• Wired has a list of top scientific graphics for 2012; Andrew Gelman doesn’t like some of them (more)
• Mathematics in elevator (you know, lift) scheduling, in the Wall Street Journal
• Neuroscience Fiction, in the New Yorker (what brain waves do and don’t tell us)
• Why iPad-native journalism doesn’t work
• A bloke called Tim Gowers writes about how he decided to have an operation, and about the difficulty in getting an intuitive feeling for risks.  There’s nothing particularly unusual about the story, except that it shows risk is difficult even for really smart people

The Herald (quoting the Daily Mail) asks “Is chocolate the new Viagra?“.

No, it isn’t. (more…)

Stuff has a story about an increase in sleeping-pill prescriptions in young people.

The increase in prescriptions is real. What’s more dubious is the explanation that it reflects an increase in sleeping difficulties is being caused by electronic devices, rather than trends in treatment.  It’s not that it’s implausible for gadgets to affect sleep — the mechanisms are fairly clear — it’s more that there isn’t any evidence supplied that sleeping problems are becoming hugely more common.

With the help of the Google and PubMed, I found a few papers looking at time trends in sleep. A recent US paper looked at time-use studies from 1975 to 2006, and found that

Unadjusted percentages of short sleepers ranged from 7.6% in 1975 to 9.3% in 2006.

A Finnish study  found about a 4% decrease in average sleep duration from 1972 to 2005, about half a minute per year.

Other research in both kids and adults seems to agree that sleep duration is decreasing slowly, but not by anything like enough to justify Stuff’s lead:

Your tablet computer, smartphone or other mobile device could be the reason you are not sleeping – and the ubiquitous devices are being cited as a possible cause for a 50 per cent jump in the number of young people scoffing sleeping pills.

It doesn’t make matters better that the “50 per cent jump” is really just for one region in NZ (the Waikato). Or that taking a single 165mg tablet per night is described as “scoffing sleeping pills”.

Stuff’s headline “Heart drug warning from Kiwi doctor” should perhaps have been “Heart drug reassurance from Kiwi doctor”.  It’s not a bad story, but some additional background might be helpful. Or interesting. Or something.

Beta-blockers block part of the body’s response to adrenaline, and are used for several quite different reasons.  They were one of the early treatments for high blood pressure, they are given after heart attacks, they are used to treat congestive heart failure (where the heart doesn’t pump effectively), and they are also used occasionally for their ability to block some of the physical symptoms of anxiety (and so are banned as performance-enhancing in some sports).  The ‘Kiwi doctor’, cardiologist Chris Nunn, is concerned that a study looking at beta-blocker use mostly for preventing serious heart disease might be misinterpreted by patients taking beta-blockers to treat serious heart disease.

The research study, published in the leading medical journal JAMA, was motivated by concern over the use of beta-blockers after heart attack being generalised to people who had not had a heart attack.  The abstract begins

β-Blockers remain the standard of care after a myocardial infarction (MI). However, the benefit of β-blocker use in patients with coronary artery disease (CAD) but no history of MI, those with a remote history of MI, and those with only risk factors for CAD is unclear.

The study is observational. That is, in contrast to the randomised experiments done with people who have had heart attacks or heart failure, this study didn’t assign people to beta-blockers.  The researchers just looked at who was and wasn’t taking the drugs, trying to get a fair comparison by matching users and non-users using a technique called propensity scores.   The idea behing propensity scores is that you will only get a bias from some other variable if it affects the chance of taking beta-blockers, so you can summarise all the available variables by a single score measuring their influence on the probability of taking beta-blockers.   This technique only works if you measure all the relevant variables (which you don’t) and you get exactly the right model for producing the propensity score (which, again, you don’t), so it’s less reliable than random assignments of treatment.  Even so, the study results in people who have had a heart attack were pretty consistent with the benefits seen after heart attack in randomised studies.

The results in people who had not had a heart attack are also consistent with randomised trials.  Since everyone in the study was seeing a doctor at least at enrollment, most of them were taking high blood pressure medication, and often of more than one kind.  One explanation of the lack of benefit from beta-blockers is just that they are less effective on average than some other high blood pressure medications in preventing heart disease and stroke. That is what was found in a combined analysis of randomised trials by a group including me, about ten years ago, and in some other similar analyses.

So.  Beta-blockers after heart attack or in heart failure are good. Beta-blockers in people with high blood pressure but not heart disease might be less effective than alternatives, but New Zealand guidelines (eg) already take all this into account, so the new study shouldn’t cause any changes in practice here.

I’ve commented a number of times about stories in the papers where researchers have, basically, dripped herbal tea on cancer cells in a Petri dish and found it killed them (the cells, not the researchers).  Screening anticancer compounds this way does work, it’s just that it doesn’t work very often, and when it does work it’s just the first step of years of likely failure.

Derek Lowe, at In The Pipeline, writes today about a research paper looking for things that might kill cancer stem cells.  These are a tiny fraction of cells in a tumour, but are thought to be responsible for a lot of the treatment resistance and relapse.  The researchers couldn’t work with actual cancer stem cells, which aren’t available in large quantities, so they used imitations produced by gene knockout. They screened 300 000 compounds from a large collection maintained by the National Institutes of Health.  About 3000 killed the imitation stem cells.  They then threw out all the compounds known to be highly toxic to normal cells, and those that repeatedly show up in screens for interesting properties.  The problem with the latter group is that either they cheat (ie, they interfere with the assays being used) or they really do so many different things that they probably won’t be practical tools.

Of the remaining 2200 compounds that killed the imitation stem cells, nearly all of them also killed the original cancer cells that didn’t have the gene knockout, so however they might work it’s probably nothing useful for cancer stem cells.  Finally, they rechecked the results with independent samples of the compounds (since if you have a collection of 300 000 compounds, no matter how careful you try to be, they aren’t all going to be what they say on the tin).

After all of this, they ended up with two compounds that appear to be selectively toxic against cancer stem cells.  These aren’t drugs, even potentially, but they should be useful for finding out more about the biological differences in cancer stem cells and that, in turn, may lead to new treatments.

According to the Herald, a West Island eye expert says that ‘up to’  5% of people who watched the solar eclipse will have permanent eye damage in the form of a blind spot or black spot in the center of their vision.  That could easily be hundred thousand people in New Zealand, which seems (a) excessive and (b) rather light on supporting data for such an important public health claim.

Auckland eye doctor Sarah Welsh is quoted as being a bit more realistic

… anyone who watched the event with the naked eye could have damaged their retina.

She had seen at least one patient today who believed they damaged their eyes yesterday….

Yet Welsh said it was “unlikely” five per cent of people suffered such burns.

“I’m not sure where he got that number from,” she said.

A brief session with the internets reveals that after a 1999 eclipse in Britain, there were 14 confirmed cases of permanent eye damage. The same eclipse was also seen in Stockolm, Sweden, where there were 15 cases recorded.  And in 1995, an eclipse in Pakistan led to 36 cases at the Abbottabad Hospital, 26 of whom recovered completely.  There will be some under-reporting in all these examples, but it’s hard to imagine that only one in a hundred or one in a thousand of the people with eye damage reports it.

So where did the 5% number come from? It probably sounded plausible.  That is, he pulled it out of his hat. Or somewhere else round and inappropriate.

The Herald’s story about perinatal mortality in the Counties Manukua DHB area is informative and statistically sensible.  They also have a story about stillbirths, with actual data and expert comments.

The Herald (from the Daily Mail, sadly) has a headline “Baby girls exposed to stress have great risk of teen anxiety”.  “How great?”, you ask. They don’t say.

We do learn:

Teenage girls are more likely to struggle with anxiety and depression if they’re exposed to stress as babies, a study has found.

If you go to look at either the abstract, or the more comprehensible explanation in Nature News, you find that this isn’t quite right

Overselling the significance of medical research is a familiar problem in the media, with scientists and journalists both being culpable.  There’s a dramatic example going on at the moment, where Pluristem Therapeutics, who made available their in-development treatment on compassionate grounds to three patients, issued press releases with titles such as “Compassionate Use of Pluristem’s PLX Cells Saves the Life of a Child After Bone Marrow Transplantation Failure.” The child died six months later.  One of the other two patients has also died.

Bloomberg News is the main source for this story, and they focused on the impact on share prices and whether the reporting might have violated stock-market regulations, which an expert quoted in the story says is a grey area, and the company denies:

The Haifa, Israel-based company doesn’t follow patients after they are released from the hospital and wasn’t obligated to report the girl’s death, he said.

“What counts legally is whether there is an improvement in the physical condition,” Aberman said in a telephone interview with Bloomberg News. “When we saw significant improvement in the blood count, we declared a successful treatment.”

Even assuming that excitement with the progress of their new treatment was the only factor in the press releases, the whole miracle-cure thing is irresponsible.  Leigh Turner, a bioethicist from Minnesota, (in a blog interview) said it well:

There are some valuable lessons here both for reporters as well as for consumers of news coverage of stem cell research and other areas of science that are routinely overhyped. Whose interests are served when press releases are issued? Is there something significant about timing of press releases? Are independent voices included in news coverage or do all quoted individuals have vested interests in promoting positive account of study results? Why is a press release being issued if results are based upon a single research participant or merely a few research subjects? And finally, what financial interests are swirling beneath the language of “miracles”, “cures”, and “lifesaving” interventions? These are questions reporters should ask and they are also questions those of us who read and otherwise consume the news should consider whenever we are confronted with dramatic claims floated on anecdotes, testimonials, and research “findings” based on meaningless sample sizes.

Pluristem’s work, with placental stem cells, is promising, and they have actual clinical trials starting and planned. That’s how we will be able to tell whether the treatments help patients, and that is what might be worth reporting. (via)

Two stories in the Herald today have the related theme of health problems where we know the answer in theory, just not how to get it done in practice.

Prof. Norman Sharpe, from the Heart Foundation, describes NZ’s record on rheumatic fever as ‘shameful’.  I’d put it differently. NZ’s record on child poverty is shameful. The record on rheumatic fever is embarrassing.  Rheumatic fever is an anachronism. You couldn’t even put it in a soap opera nowadays.  It’s the sort of obscure historical disease that appears in ‘House‘.

Economic inequality is a major reason why the underlying infections spread widely in some subsets of Kiwi kids, but that isn’t the whole story.  The US and the UK have child poverty, but they don’t have rheumatic fever.  Rheumatic fever is an autoimmune reaction to untreated streptococcal throat infections.  Unlike many infectious diseases where antibiotic resistance is a problem, these streptococci are uniformly susceptible to ordinary penicillin. The cost to Pharmac of a 10-day course of penicillin is about $5,  but we obviously haven’t managed to set up an infrastructure that will reliably get the treatment to the kids who need it.

The other story had the slightly-misleading lead

Letting children out to play on their own could do a lot more to combat obesity, rather than structured exercise, a study shows.

The study actually looked about attitudes to ‘active play’ and ‘physical exercise’ in kids and families in a South Auckland school. The researchers found that ‘physical exercise’ was regarded as healthy, but active play was regarded as fun.  They suggest that encouraging kids to play outside in an unorganised way would be a more effective way of getting them to exercise.  We don’t know if this will actually work, but it is targetting the right part of the problem.  We know that exercise improves health, we just don’t know what to do to get people to exercise.

[Update: On Twitter, @dr2go says NZ isn’t an outlier.  That’s true for NZ as a whole, and the rates in Pakeha are similar to those in US whites.  I don’t think it’s true for Maori or Pacific children,  where the rates are higher even than US minority groups had in the 1960s (reference), and there’s been a big decline since then]