Posts filed under Medical news (341)

Today Stuff tells us that talcum powder, dogs, barbecues, fish oil, oral sex, and air travel cause cancer.  The statistic on dogs is especially bizarre

Analysis of breast cancer cases by researchers at the University of Munich showed that 79.7 per cent of all breast cancer patients had regular contact with dogs before diagnosis. Only 4.4 per cent of the patients did not have pets at any time, compared to 57.3 per cent of a healthy control group. According to researchers, that’s a 29-fold increased risk for pet owners.

Given that the lifetime risk of breast cancer is roughly 10%, a 29-fold increase seems a bit improbable. That’s more than the increase in lung cancer risk caused by smoking, for example.

It’s interesting to track this one down. An obvious place to start is the “Kill or Cure?” website that collects Daily Mail stories about cancer.  Back in 2007, the Mail reported what looks like the same story

Analysis of breast cancer cases by researchers at the University of Munich showed that patients with this type of cancer were significantly more likely to have kept a dog than a cat.

In fact, 79.7 per cent of all patients had intensive contact with dogs before they were diagnosed.

Only 4.4 per cent of the patients did not have pets at any time compared to 57.3 per cent of a healthy control group ? so there was a 29-fold increased risk for pet owners.

They didn’t link either, but the story looks like it comes from this publication (and if you can get to the full-text article you find that the numbers match).

The first thing to note is that the journal is Medical Hypotheses, notoriously “intended as a forum for unconventional ideas without the traditional filter of scientific peer review,

The second thing to note is the relative risk given in the abstract: 3.5, not 29.  The number ’29’ does appear later in the paper, but even the authors aren’t prepared to defend it much.

The third thing to notice is what comparison was actually done

 It became apparent that patients with breast carcinoma (N=69) owned significantly more often dogs but not cats compared to age matched female controls. We compared the frequencies of dog and pet ownership with data from public available statistics on women (N=1320) of the same age group in Bavaria.

That is, they asked a small number of patients with breast cancer about close contact with dogs, but used public statistics on pet ownership for the controls.  Using different methods of obtaining information in cases and controls is a notorious way to come up with spurious results.

The theory was that dogs and humans shared a virus that caused breast cancer.  There have been some reports of finding genetic material that looks like this virus in breast tumours, but other reports that did not, including an Australian research paper that looked very carefully.

Chocolate tastes nice but (sadly) is high in fat, so there’s a lot of potential appeal in news stories that say it’s really terribly healthy. Ideally these stories would come out just before Valentine’s Day, or Christmas, or perhaps Mothers’ Day, but any time of the year will do.

The Herald has a chocolate story, with the lead

Hot chocolate can help older people keep their brains healthy, research has shown.

The research compared blood flow in the brain, and performance on some cognitive function tests. The participants were assigned to drink cocoa with high or low levels of flavonols (aka flavonoids), the chemicals in chocolate that are thought to possibly have beneficial effects.  Based on the headline, you might expect that the researchers saw a difference between the two groups. Sadly, no:

Half the participants were given hot chocolate rich in antioxidant flavanol plant compounds while the other half received low-flavanol cocoa.

Flavanol content made no difference to the results, the researchers found.

That is, participants in both groups improved over the course of the study, regardless of what they drank.  Normally, this would be considered evidence against an effect of chocolate.

For comparison, there’s a more careful story at NPR news, and a less careful one at Forbes. We repeat the  StatsChat position on chocolate “Don’t eat it just for health reasons. If you don’t like it, save it for people who do.”

• Some 1920-30s cartograms (distorted maps) of the USA, at Making Maps. Here’s the one based on electricity use
  
• Another map: the USA has low income mobility (ie, children of the poor stay poor), but there is quite a lot of variation over the country. This is the version of the map from the original researchers, click for the shiny interactive New York Times version
  
• A good story about a new randomized trial of a melanoma vaccine, based on NZ research.  The story even says that the trial is measuring specific components of immune response, not (yet) actual disease.  As should always be the case, the trial is registered and there’s more detail at the registry.
• A post about wild extrapolation in estimating the value of marine reserves to (UK) anglers:
  Or you could look at the Celtic Deep rMPA, a site located some 70km offshore, where they estimate between 145,000 and 263,000 angling visits per year. That’s 400-720 visits a day, which translates to approx 40-70 typical sea angling boats, each full to the gunwales every single day of the year.

The New York Times has a detailed story about one of the triggers for the Alltrials campaign, the missing studies of Tamiflu

He was curious about one of the main studies on which Dr. Jefferson had relied in his previous analysis. Called the Kaiser study, it pooled the results of 10 clinical trials. But Dr. Hayashi noticed that the results of only two of those trials had been fully published in medical journals. Given that details of eight trials were unknown, how could the researchers be certain of their conclusion that Tamiflu reduced risk of complications from flu?

Only about half of all randomized clinical trials are published, despite regulations requiring publication, and the requirements of the Declaration of Helsinki

Authors have a duty to make publicly available the results of their research on human subjects and are accountable for the completeness and accuracy of their reports.

Since the obvious conclusion is that the unpublished studies are less favorable than the published ones, patients and the medical community cannot be sure about the benefits of even the most promising treatments.  The uncertainty always matters at least to a small group of patients, but in the case of Tamiflu it matters to the whole world. The 2009-2010 influenza pandemic was relatively minor, but still killed more than 250000 people worldwide (by most estimates, more than the Iraq war). The 1918 pandemic was at least twenty times worse. Before it happens again, we need to know which treatments work and which do not work.

Stuff has a (mostly reasonable) story on alcohol and cancer, quoting Prof Doug Sellman

“The ethanol in alcohol is a group one carcinogen, like asbestos,” 

Many of the readers of this story won’t know what a “group one carcinogen” is.  Given the context, a reader might well assume that “group one carcinogens” are those that carry the largest risks of cancer, or cause the most serious cancers. In fact, all it means is that an additional hazard of cancer, whether high or low, has been definitely established, because that’s all the IARC review process tries to do. The Preamble to the IARC Monographs that define these carcinogens says

A cancer ‘hazard’ is an agent that is capable of causing cancer under some circumstances, while a cancer ‘risk’ is an estimate of the carcinogenic effects expected from exposure to a cancer hazard. The Monographs are an exercise in evaluating cancer hazards, despite the historical presence of the word ‘risks’ in the title. The distinction between hazard and risk is important, and the Monographs identify cancer hazards even when risks are very low at current exposure levels, because new uses or unforeseen exposures could engender risks that are significantly higher.

Group 1 carcinogens tend to either be very common exposures or to cause very specific types of cancer, because those are the two scenarios that make it easy to establish definitely that there is a risk.  They include asbestos, arsenic, sunlight, birth control pills, plutonium, diesel exhaust, and wood dust.

Some group 1 carcinogens, such as tobacco and hepatitis B, are responsible for large numbers of cancer deaths worldwide. Others, such as plutonium and diethylstilbestrol, are responsible only for small numbers of deaths. Some group 1 carcinogens cause aggressive, untreatable tumours; for others, such as human papillomavirus, disease is largely preventable by screening; still others, such as sunlight, sometimes cause serious disease but mostly cause relatively minor tumours.

The phrase “group one carcinogen” is only relevant in an argument over whether the risk is zero or non-zero. Its use in other contexts suggests that someone doesn’t know what it means, or perhaps hopes that you don’t.

More on the ongoing fluoridation story:

Firstly, there is a very good statement from the PM’s chief science adviser, Peter Gluckman.  As he says, the scientific issues are entirely settled: at the concentrations used in treating water, fluoride reduces tooth decay and does not cause any harm.  At one time there was scientific uncertainty about adverse health effects; this is just not the case any more.  There is still a question of whether you want to treat the whole population in this way.  We add iodine to salt and folate to bread, but these prevent more serious illnesses than fluoridation does, and there are fewer people with an irrational fear of iodine or folate.

Second, the Herald has a Digipoll on fluoridation

The poll showed 48 per cent of New Zealanders supported the addition of fluoride – double the 25 per cent of those who opposed its use. A further 24 per cent believed the issue should be left to local councillors to decide.

Unfortunately, the poll tried to use a single question to address two unrelated issues: do you want fluoride in your water?, and should the decision be made nationally or locally?  As a consequence, it’s hard to interpret the results.  The ratio of for:against is about the same as in the Hamilton referendum that started fluoridation there in 2006, but if you assume all the people who want the issue decided locally  are really against fluoridation, the opinion would be nearly 50:50.  It obviously isn’t reasonable to assume everyone in favour of local decision-making is against fluoridation — I’m on record as a counterexample — but there’s no way to know how these folks would split.

The Herald story goes on to quote an antifluoride lobbyist

Ms Byrne said the group had science to back its claims that fluoride was toxic and harmful when added to water and without applying it directly to teeth offered none of the benefits health authorities claimed.

However, that is hotly disputed within the science community.

It’s not disputed within the scientific community, it’s disputed by the scientific community. The science, as Sir Peter observes, is settled.

From the World Conference of Science Journalists, via @roobina (Ruth Francis), ten tweets on reporting clinical trials

1. Was this #trial registered before it began? If not then check for rigged design, or hidden negative results on similar trials.
   
2. Is primary outcome reported in paper the same as primary outcome spec in protocol? If no report maybe deeply flawed.
3. Look for other trials by co or group, or on treatment, on registries to see if it represents cherry picked finding
4. ALWAYS mention who funded the trial. Do any of ethics committee people have some interest with the funding company
5. Will country where work is done benefit? Will drug be available at lower cost? Is disorder or disease a problem there
6. How many patients were on the trial, and how many were in each arm?
7. What was being compared (drug vs placebo? Drug vs standard care? Drug with no control arm?
8. Be precise about people/patient who benefited – advanced disease, a particular form of a disease?
9. Report natural frequencies: “13 people per 10000 experienced x”, rather than “1.3% of people experienced x”
10. NO relative risks. Paint findings clearly: improved survival by 3%: BAD. Ppl lived 2 months longer on average: GOOD

Who says you can’t say anything useful in 140 characters?

Allan Hansen sends in this infographic from Greatist, showing the benefits of quitting smoking

He points out the non-linear time scale — equally spaced intervals range from 20 minutes to five years.  It’s also a bit strange that time progresses in the opposite direction to the burning of the cigarette — perhaps it should have been flipped left to right.

Other versions of this information are common, and they nearly all have the same nonlinear time scale

One notable exception is from Blisstree, where the evenly-spaced text is linked to accurately-scaled times by lines.  This graphic also avoids the direction-of-burning problem, using comments from former smokers as the background.

We keep going on here about the importance of publishing clinical trials.  Today (in Britain), the BBC program Panorama is showing a documentary about a doctor who has been running clinical trials of the same basic treatment regimen for twenty years, without publishing any results. And it’s not that these are trials that take a long time to run — the participants have advanced cancer. If the treatment was effective, it would have been easy to gather and publish convincing evidence by now, many times over.

These haven’t been especially good clinical trials by usual standards — not randomized, not controlled — and they have been anomalous in other ways as well. For example, patients participating in the trial are charged large sums of money for the treatment being tested (not just for other care), which is very unusual.  Unusual, but not illegal.  Without published evidence that the treatment works, it couldn’t be sold outside trials, but it’s still entirely legal to charge money for the treatment in research. It’s a bit like whaling.

According to the BBC, Dr Burzynski says it’s not his decision to keep the results secret

He said the medical authorities in the US would not let him release this information: “Clinical trials, phase two clinical trials, were completed just a few months ago. I cannot release this information to you at this moment.”

If true, that would be very unusual. I don’t know of any occasion when the FDA has restricted scientific publication of trial results, and it’s entirely routine to publish results for treatments that have not been approved or even where other research is still ongoing. The BBC also checked with the FDA:

But the FDA told us this was not true and he was allowed to share the results of his trials.

This is all a long way away from New Zealand, and we can’t even watch the documentary, so why am I mentioning it? Last year, the parents of an NZ kid were trying to raise money to send him to the Burzynski clinic, with the help of the Herald.   You can’t fault the parents for trying to buy hope at any cost, but you sure can fault the people selling it.

Wikipedia has pretty good coverage  if you want more detail.

The Herald, writing about Hamilton’s pending removal of fluoridation from their water supply

A Hamilton City Council tribunal examining the topic has re-ignited intense public debate on the issue, with 89 per cent of the 1,557 submissions made to it in favour of stopping fluoridation. In 2006, 70 per cent of residents who voted in a referendum backed fluoride.

This actually isn’t evidence or even a suggestion of a change in opinion. All we can tell from the numbers is that 1386 people now want fluoride removed.  Public submissions are useful qualitatively, not quantitatively.

It may be true that the people of Hamilton don’t want fluoride in their water, in which case I think they are unwise, but it’s their problem. Confusing self-selected numbers with referendum votes  isn’t going to help determine what they want, [and neither is the exclusion from voting of three of twelve council members on the grounds that they also sit on the DHB and so have thought about the issues before]