Posts filed under Medical news (257)

October 22, 2014

Screening the elderly

I’ve seen two proposals recently for population screening of older people. They’re probably both not good ideas, but for different reasons.

We had a Stat of the Week nomination for a proposal to screen people over 65 for depression at ordinary GP visits, to prevent suicide. The proposal was based on the fact that 70% of the suicides were in people who had visited a GP within the past month.  If the average person over 65 visits a GP less than about 8.5 times a year, this means those visiting their GP are at higher risk.  However, the risk is still very small: 225 over 5.5 years is 41/year, 70% of that is 29/year.

To identify those 29, it would be necessary to administer the screening question to a lot of people, at least hundreds of thousands. That in itself is costly; more importantly, since the questionnaire will not be perfectly accurate there will be  tens of thousands of positive results. For example, a US randomised trial of depression screening in people over 60 recruited 600 participants from 9000 people screened. In the ‘usual care’ half of the trial there were 3 completed suicides over the next two years; in those receiving more intensive and focused help with depression there were 2. The trial suggests that screening and intensive intervention does help with symptoms of major depression (probably at substantial cost), but it’s not likely to be a feasible intervention to prevent suicide.


The other proposal is from the UK, where GPs will be financially rewarded for dementia diagnoses. In contrast to depression, dementia is pretty much untreatable. There’s nothing that modifies the course of the disease, and even the symptomatic treatments are of very marginal benefit.

The rationale for the proposal is that early diagnosis gives patients and their families more time to think about options and strategies. That could be of some benefit, at least in the subset of people with dementia who are able and willing to talk about it, but similar advance planning could be done — and perhaps better — without waiting for a diagnosis.

Diagnosis isn’t like treatment. As a British GP and blogger, Martin Brunet, points out

We are used to being paid for things of course, like asthma reviews and statin prescribing, and we are well aware of the problems this causes – but at least patients can opt out if they don’t like it.

They can refuse to attend a review, decline our offer of a statin or politely take the pill packet and store it unopened in the kitchen cupboard. They cannot opt out of a diagnosis.


October 9, 2014

…and to divide the light from the darkness

Q: There’s a story that charging your phone in your bedroom make you fat.

A: Yes, there is.

Q: Why?

A: Because it looked like a good headline.

Q: No, why does it make you fat?

A: Melatonin. The theory is that any light at night time makes your body not produce enough melatonin and that this is bad.

Q: How much more did people who charged their phones in their bedroom end up weighing?

A: There weren’t any people involved.

Q: Ok, so they had mice with cellphones in their bedrooms?

A: Rats. And not cellphones.

Q: Some other light source of a similar brightness?

A: No.

Q: What, then?

A: They put melatonin in the rats’ drinking water.

Q: So that should make them lose weight. Did it?

A: Not that they reported.

Q: Can you work with me here?

A: They measured the conversion of fat under the rats’ skin from ‘white’ to ‘brown‘, which is theoretically relevant to energy use and perhaps to diabetes and heart disease. It’s interesting research. (abstract)

Q: So it could be relevant, but doesn’t the generalisation seems a bit indirect?

A: Yes, “a bit.”

Q: Do international patterns of cellphone use match patterns of obesity?

A: Not really, but maybe in East Asia they use different chargers or something.

Q: Is the LED on a charger really enough to make a difference?

A: That’s what the story lead implies, but the second paragraph talks about research involving phone screens, laptops, artificial lighting, and street lights, so I’m guessing there’s a bit of a bait and switch going on.

Q: Couldn’t it be enough? I mean, in nature, it would be completely dark at night, like they say.

A: Only up to a point. There was another relevant story today, too.


October 3, 2014

Antibiotics, kids, and obesity

Earlier this week, the Herald had a story about antibiotics and childhood obesity. No-one involved really covers themselves in glory here, but probably the reporter comes out best.

The headline (Antibiotics ‘link to child obesity’) with appropriate claim quotes, and the lead

Children who are given antibiotics in the first two years of their lives are at greater risk of becoming obese in early childhood, a study suggests.

are fine, though there’s a sub-headline “Study finds some treatments kill bacteria that affect rate at which toddlers gain fat” that manages to be wrong in every respect.

The story goes on

The United States research is based on the medical records of 65,000 children between 2001-2013.

Researchers found infants who were given broad-spectrum antibiotics at least four times in their first two years were 16 per cent more likely to be obese by the age of 5.

That is in the research paper, but it’s much less impressive in context


The circles are the observed ratios of rates of obesity, the lines give the margin of error. You can see that, compared to no exposure, one exposure seems bad, two or three not so bad, and four or more worse.  They’ve looked at a lot of comparisons that don’t show a clear pattern, and picked out the biggest number.

There are other quibbles, for example, ‘broad spectrum’ doesn’t mean what it usually means, it means ‘everything except penicillin and amoxicillin’, but the biggest problem is confounding.  There are lots of things related to obesity and to antibiotic prescription, and it wouldn’t be at all surprising for one of them to explain this relationship.

More importantly, there’s no way this explains any meaningful fraction of the increase in childhood obesity.  Only about 3% of children were in the ‘4+ broad spectrum exposures’, so even if the ratio of 1.16 was true, the antibiotics would only be responsible for about half a percentage point of the obesity rate.  Even less of the the obesity increase would be explained, since antibiotics aren’t actually completely new.  Differences between countries also don’t seem to fit this as an explanation. For example, South Korea used to have a serious antibiotic overuse problem, which was reduced by new regulations in 2000. They don’t have much of a childhood obesity problem.

Still, there’s no reason the result couldn’t be true to some extent.  Antibiotics do affect gut bacteria, and gut bacteria are important in metabolising food. It might be true, but it’s definitely being oversold, and there are more urgent reasons not to over-use broad spectrum antibiotics.

The other part of the story that’s disappointing for the light it casts on science communication is some of the response

Some New Zealand experts are sceptical. Fight the Obesity Epidemic founder Dr Robyn Toomath noted that the latest study was funded by the American Beverage Foundation for a Healthy America, founded by the soft-drink industry.

“This is the industry buying crap science,” she said. “People who are poor get sick and get more antibiotics. They are more likely to be fat and a lot of other things as well.”

I’m in favour of scientists commenting on public issues, and I don’t see anything wrong with advocacy, but I think public allegations of intellectual dishonesty need a bit more detailed backup than this. You’d almost get the impression that the research hadn’t looked at number of doctors visits or any indicators of poverty.

September 26, 2014

Screening is harder than that

From the Herald

Calcium in the blood could provide an early warning of certain cancers, especially in men, research has shown.

Even slightly raised blood levels of calcium in men was associated with an increased risk of cancer diagnosis within one year.

The discovery, reported in the British Journal of Cancer, raises the prospect of a simple blood test to aid the early detection of cancer in high risk patients.

In fact, from the abstract of the research paper, 3% of people had high blood levels of calcium, and among those,  11.5% of the men developed cancer within a year. That’s really not strong enough prediction to be useful for early detection of cancer. For every thousand men tested you would find three cancer cases, and 27 false positives. What the research paper actually says under “Implications for clinical practice” is

“This study should help GPs investigate hypercalcaemia appropriately.”

That is, if a GP happens to measure blood calcium for some reason and notices that it’s abnormally high, cancer is one explanation worth checking out.

The overstatement is from a Bristol University press release, with the lead

High levels of calcium in blood, a condition known as hypercalcaemia, can be used by GPs as an early indication of certain types of cancer, according to a study by researchers from the universities of Bristol and Exeter.

and later on an explanation of why they are pushing this angle

The research is part of the Discovery Programme which aims to transform the diagnosis of cancer and prevent hundreds of unnecessary deaths each year. In partnership with NHS trusts and six Universities, a group of the UK’s leading researchers into primary care cancer diagnostics are working together in a five year programme.

While the story isn’t the Herald’s fault, using a photo of a man drinking a glass of milk is. The story isn’t about dietary calcium being bad, it’s about changes in the internal regulation of calcium levels in the blood, a completely different issue. Milk has nothing to do with it.

Paracetamol and ADHD reporting

Everyone has a story about the new Auckland findings of correlation between paracetamol use in pregnancy and ADHD in kids.

Almost uniformly they don’t make it easy to the find actual (open-access) research paper, not even naming the journal: NZ Doctor’s reprint of the press release does best, with

“The study was published [date] in Plos One online at this link;” [sic]

without a link or a date. The paper is here.

The other thing the stories don’t really make clear is that this finding is important only because it confirms the surprising finding from a big Danish study published earlier this year. The evidence from the New Zealand research wouldn’t be at all convincing on its own, but the replication of an association with paracetamol but not other commonly-used medications is potentially important.   Even the Science Media Centre didn’t really make this clear in their post, though the University of Auckland website does better.

It’s still quite possible that chance or confounding explains this association, and we don’t know if other groups tried to replicate the association and failed, but the replication is a significant step.

September 25, 2014

Asthma and job security

The Herald’s story is basically fine

People concerned that they may lose their jobs are more likely to develop asthma than those in secure employment, a new study suggests.

Those who had “high job insecurity” had a 60 per cent increased risk of developing asthma when compared to those who reported no or low fears about their employment, they found.

though it would be nice to have the absolute risks (1.3% vs 2.1% over two years) , and the story is really short on identifying information about the researchers, only giving the countries they work in (the paper is here).

The main reason to mention it is to link to the NHS “Behind the Headlines” site, which writes about stories like this one in the British Media (the Independent, in this case).

Also, the journal should be complimented for having the press release linked from the same web page as the abstract and research paper. It would be even better, as Ben Goldacre has suggested, to have authors listed for the press release, but this is at least a step in the direction of accountability.

September 22, 2014

Blame it all on mum

Says the Herald (reprinting the Daily Mail)

If you have always found doing sums a struggle, you might just be able to blame your mother.

Because research has linked a woman’s hormone levels in pregnancy with her child’s maths skills at age five.

Boys and girls whose mothers were very low in the hormone thyroxine were almost twice as likely to do badly in arithmetic tests, it found.

The hormone in question is thyroxine, produced by the thyroid, and the basic issue is that iodine deficiency is getting more common again. In Australia and New Zealand, iodine has been added to bread since September 2009 to address this problem. In Australia, the fortification of bread has been fairly successful; there doesn’t seem to be data for New Zealand, but there’s no reason to expect it to be different. So the story  may not be applicable to New Zealanders.

Also, as with the cannabis paper a couple of weeks ago, the “twice as likely” is simply wrong.  Doing badly in arithmetic was defined as being in the bottom 50%, and it’s not plausible that low-thyroxine kids are twice as likely to be in the bottom half.  In fact, it’s the odds ratio for being in the lower 50% of students in maths that was 1.79.  Since the overall odds of being in the bottom half is 1:1, if you multiply by 1.79 you get 1.79:1, which is a probability of 64% of being in the bottom half.

A difference between 50% and 64% is not “almost twice as likely”, and “blame” is a completely inappropriate term — this is new research, so even if it’s true (it could be) and relevant to New Zealand (it probably isn’t) it would not be something for which ‘blame’ would be appropriate. There’s entirely too much blaming mothers already.

September 18, 2014

Bald truth

From the Herald

Men who are bald at age 45 are more likely to develop aggressive prostate cancer compared with those who keep their hair.

US researchers found those who lose hair at the front of their heads and have moderate hair-thinning on the crown were 40 per cent more likely to develop a fast-growing tumour in their prostate.

This was compared with men with no baldness.

That’s all true, but what casts doubt on this finding is that you get the same results if you compare to men with severe baldness. That is, the research found a higher rate of aggressive prostate cancer in men who had ‘moderate’ baldness on the top of head, but not in those who had milder or more severe forms, and no increase in non-aggressive prostate cancer. Here are the estimated relative increases in risk, with confidence intervals


When you consider the lack of a consistent trend, and the fact that the evidence isn’t all that strong for the moderate-baldness/aggressive-cancer combination, I don’t think this is worth getting all that excited about.

This one can mostly be blamed on the journal: the American Society of Clinical Oncology press release isn’t too bad in itself, but if you compare it to the other recent occasions when ASCO have issued a press release, it doesn’t really measure up.

September 10, 2014

Cannabis graduation exaggeration


Teenagers who use cannabis daily are seven times more likely to attempt suicide and 60 percent less likely to complete high school than those who don’t, latest research shows.

Me (via Science Media Center)

“The associations in the paper are summarised by estimated odds ratios comparing non-users to those who used cannabis daily. This can easily be misleading to non-specialists in two ways. Firstly, nearly all the statistical evidence comes from the roughly 1000 participants who used cannabis less than daily, not the roughly 50 daily users — the estimates for daily users are an extrapolation.

“Secondly, odds ratios are hard to interpret.  For example, the odds ratio of 0.37 for high-school graduation could easily be misinterpreted as a 0.37 times lower rate of graduation in very heavy cannabis users. In fact, if the overall graduation rate matched the New Zealand rate of 75%, the rate in very heavy cannabis users would be 53%, and the rate in those who used cannabis more than monthly but less than weekly would be 65%.

That is, the estimated rate of completing high school is not 60% lower, it’s about 20% lower.  This is before you worry  about the extrapolation from moderate to heavy users and the causality question. The 60% figure is unambiguously wrong. It isn’t even what the paper claims.  It’s an easy mistake to make, though the researchers should have done more to prevent it, and that’s why it was part of my comments last week.

You can read all the Science Media Centre commentary here.


[Update: The erroneous '60% less likely to complete high school' statement is in the journal press release. That's unprofessional at best.]

(I could also be picky and point out 3News have the journal wrong: The Lancet Psychiatry, which started this year, is not the same as The Lancet, founded in 1823)

August 30, 2014

Funding vs disease burden: two graphics

You have probably seen the graphic from vox.comhyU8ohq


There are several things wrong with it. From a graphics point of view it doesn’t make any of the relevant comparisons easy. The diameter of the circle is proportional to the deaths or money, exaggerating the differences. And the donation data are basically wrong — the original story tries to make it clear that these are particular events, not all donations for a disease, but it’s the graph that is quoted.

For example, the graph lists $54 million for heart disease, based on the ‘Jump Rope for Heart’ fundraiser. According to Forbes magazine’s list of top charities, the American Heart Association actually received $511 million in private donations in the year to June 2012, almost ten times as much.  Almost as much again came in grants for heart disease research from the National Institutes of Health.

There’s another graph I’ve seen on Twitter, which shows what could have been done to make the comparisons clearer:



It’s limited, because it only shows government funding, not private charity, but it shows the relationship between funding and the aggregate loss of health and life for a wide range of diseases.

There are a few outliers, and some of them are for interesting reasons. Tuberculosis is not currently a major health problem in the US, but it is in other countries, and there’s a real risk that it could spread to the US.  AIDS is highly funded partly because of successful lobbying, partly because it — like TB — is a foreign-aid issue, and partly because it has been scientifically rewarding and interesting. COPD and lung cancer are going to become much less common in the future, as the victims of the century-long smoking epidemic die off.

Depression and injuries, though?


Update: here’s how distorted the areas are: the purple number is about 4.2 times the blue number