Posts filed under Medical news (341)

Nicely summarised by two paragraphs from a story in the Herald

In a separate breast cancer study published online by the British Medical Journal(BMJ), researchers from Norway and the United States found that mammograms carried out once every two years may reduce death risk by about 28 per cent.

About 27 deaths from breast cancer can be avoided for every 10,000 women who did mammography screening – or about one in 368, said the team after analysing data from all women in Norway aged 50 to 79 between 1986 and 2009.

The two prevention numbers — 28% of breast cancer deaths, or one breast cancer death for every 368 women screened — are the same, but they give a very different impression. [Note that this is the age range where mammography works best]

Stuff has a story about ‘Powerhouse Fruits and Vegetables”.  They get points for linking to the source, and for pointing out that although

“The rankings provide clarity on the nutrient quality of the different foods

the rankings are quite different from other rankings that are supposed to do the same thing.

They don’t point out that it’s silly to list scores to four digit accuracy when nutrient content varies enough to make the first digit somewhat unreliable.They also don’t point out that these are nutrient scores not per serving, but per 100 Calories of the food. Google thinks watercress has about 11 Calories/100g, so that’s 900g of watercress. The data are for raw watercress — the research paper doesn’t say how much the score goes down if you stir-fry it, Chinese-style.

If you much through a couple of pounds of watercress, it’s not surprising you’d pick up a few nutrients along the way. The applicability of this fact to NZ daily life must be a bit limited, though.

If you find that changing your diet in some way makes you feel happier and healthier, that’s a good thing.  It doesn’t matter whether the same change would be useful for most people, or only useful for you. It doesn’t matter whether the change is a placebo effect. It doesn’t even matter if it’s an illusion, a combination of regression to the mean and confirmation bias. You might check with a doctor or dietician as to whether the change is dangerous, but otherwise, go for it.

If you want to campaign for the entire community to make a change in their diet, you need to have evidence that it’s better on average for the entire community. A few people’s subjective experience isn’t good enough.  Good quality observational data might be all you can manage if the benefits are subtle or take years to appear, but if you’re claiming dramatic short-term benefits you should be able to demonstrate them in a randomised controlled trial.

The reason for mentioning this is that PETA has been making friends again. They’re trying to link milk consumption to autism. They don’t even pretend to have any evidence that milk causes autism, and the evidence that milk-free diet has a beneficial effect in people with autism is very weak.  That is, there are a few studies that suggest a benefit, but the benefit is smaller in studies with more reliable designs, and absent in the best-designed studies.  The most recent review of the evidence concluded that dairy-free or gluten-free diets should only be tried for people who have some separate evidence of food intolerance.  After reading the review, I would agree.

There are respectable arguments against dairy farming, both ethical and environmental. Scaremongering about autism isn’t one of them.

Health and evidence edition

• Evidently Cochrane, a blog with non-technical explanations of Cochrane Collaboration review results
• Design process for a graphic illustrating the impact of motorbike helmet laws.  In contrast to bicycle helmet laws, laws for motorbikes do have a visible effect on death statistics
• Stuff has quite a good story on alcohol in New Zealand.
• The British Association of Dermatologists responds to ‘drinkable sunscreen’.
• 3News piece on Auckland research into extracts of the lingzhi mushroom. Nice to see local science, and the story was reasonably balanced, with Shaun Holt pointing out that this is not even approaching being anywhere near evidence that drinking the stuff would do more good than harm.

The Daily Mail (and the Telegraph) recently ran puff pieces advertising a new ‘drinkable sunscreen’

Those who make the product, which is available to buy, claim that once the elixir is ingested, molecules of the product vibrate on the skin to cancel out 97 per cent of UVA and UVB rays.

Actually, the Telegraph headline was “Could this be the first drinkable sunscreen?”, and, following Betteridge’s Law, the answer is “Fsck, no!” A blog at the Guardian has a good demolition of the stories, and the illuminating byline

Dean Burnett is acutely aware of how many ways he could be sued if he wrote his initial reactions to the articles about this sunscreen. He is on Twitter, @garwboy

British libel law has been modified after the notorious attack on Simon Singh, but it’s not surprising that no-one wants to be a test case for the new law.

After seeing the reaction, the Mail has at least modified their article to add a concluding warning

Hermoine Lawson, spokesman at the British Skin Foundation, said: ‘We would advise extreme caution of any product claiming UV protection using methods not supported by clinical research. 

‘When it comes to an issue as serious as preventing skin cancer, customer testimonials cannot take the place of scientific evidence, for which this particular product cannot provide.

The Telegraph has a story about the implausibility of the claim and the lack of supporting evidence, though it carefully doesn’t mention how you might have come to hear about the claim, and there certainly isn’t an apology or a retraction.

That’s all on the other side of the world.  Here, where we have one of the highest rates of melanoma, you’d expect a bit more of a clue about sunscreen. But, no, One News has the story. They don’t have the testimonial from someone who used it on a toddler, but they do have the inventor claiming it is effective for more than 99% of people.

Although One News just describes them as a US skincare company, they have a New Zealand distributor with a New Zealand company registration and .co.nz website, and a whole bunch of ‘harmonized water’ products with superficially implausible claims, and they do include the ‘sunscreen’ and the claims:

•Neutralizes UV radiation 
•Allows for increased sun exposure (30x more than normal) 
•Enhances tanning effect from the sun 

Perhaps someone might like to ask the Advertising Standards Authority to verify that the claims are indeed valid and substantiated?

Video from the Alltrials campaign. It’s fair to point out that this is well-designed propaganda, even though it’s absolutely right about the problem

You can also read what a drug-discovery chemist says about the results of the campaign to get all the Tamiflu trials analysed.

A new study pooled data from previous studies of vaccination and autism, and as Emily Willingham writes, it gives what you’d expect.

Five cohort studies involving 1,256,407 children and five case-control studies involving 9920 children were included in this analysis.

• There was no relationship between vaccination and autism (OR: 0.99; 95% CI: 0.92 to 1.06).
• There was no relationship between vaccination and [autism spectrum disorder] (OR: 0.91; 95% CI: 0.68 to 1.20).
• There was no relationship between  [autism spectrum disorder] and MMR (OR: 0.84; 95% CI: 0.70 to 1.01).
• There was no relationship between  [autism spectrum disorder] and thimerosal (OR: 1.00; 95% CI: 0.77 to 1.31).
• There was no relationship between  [autism spectrum disorder] and mercury (Hg) (OR: 1.00; 95% CI: 0.93 to 1.07).

Findings of this meta-analysis suggest that vaccinations are not associated with the development of autism or autism spectrum disorder.

These results basically rule out any substantial effect due to vaccination. To the extent that they suggest any effect, it is protective, but that’s probably just chance.

This sort of result is pretty boring, so it’s unlikely to get anywhere near the same media coverage as the claims that there is an effect.

From Stuff: “New Zealand’s worst air is not where you think“.  That’s not actually true. New Zealand’s worst air, according to the story, is pretty much where I thought it would be, in coastal Canterbury and Otago.  However, if you search the Stuff website for the term “air pollution”, you get:

So if you expected Auckland to be the worst, you know who to blame.

This piece from the Vancouver Sun exaggerates the current level of usefulness of genetic tests, but is spot on about the problems of scale

“As a diagnostic tool, personal genomics is invaluable for selecting therapies, but this whole screening issue opens up another can of worms,” said Lynd. “With the new economies of scale … it is just as easy to look for everything as it is to look for the one thing you need to know.”

Every cancer patient sent for a full genome analysis to determine which variant of breast cancer she has, could potentially become a patient for any or all of the other diseases indicated on their genome and the subject of a whole series of expensive tests to disprove the presence of an illness.

From Matthew Hankins, via a Cochrane Collaboration blog post, the first few items on an alphabetical list of ways to describe failure to meet a statistical significance threshold

a barely detectable statistically significant difference (p=0.073)
a borderline significant trend (p=0.09)
a certain trend toward significance (p=0.08)
a clear tendency to significance (p=0.052)
a clear trend (p<0.09)
a clear, strong trend (p=0.09)
a considerable trend toward significance (p=0.069)
a decreasing trend (p=0.09)
a definite trend (p=0.08)
a distinct trend toward significance (p=0.07)
a favorable trend (p=0.09)
a favourable statistical trend (p=0.09)
a little significant (p<0.1)
a margin at the edge of significance (p=0.0608)
a marginal trend (p=0.09)
a marginal trend toward significance (p=0.052)
a marked trend (p=0.07)
a mild trend (p<0.09)
…

Often there’s no need to have a threshold and people would be better off giving an interval estimate including the statistical uncertainty.

The defining characteristic of the (relatively rare) situations where a threshold is needed is that you either pass the threshold or you don’t. A marked trend towards a suggestion of positive evidence is not meeting the threshold.