Posts filed under Medical news (341)

There’s an interesting story in Stuff today about an increased risk of death in people who drink lots of coffee. One of the interesting things about it is that the Herald has the same story about two weeks ago. And when I say “the same story”, I mean almost word for word the same AAP story.  I wasn’t convinced then (neither was Andrew Gelman), and it hasn’t gotten any more convincing.

The other interesting thing about the story is that the research paper was published in Mayo Clinic Proceedings. “What’s interesting about Mayo Clinic Proceedings?”, you ask, having never heard of it.  That’s my point. There are some scientific journals whose press releases you’d expect the media to monitor, and you’d expect to see stories about research papers with popular appeal. Mayo Clinic Proceedings is not really one of those journals, and it isn’t clear how this research came to the attention of AAP.

If the PubMed research database is still surviving the US government shutdown, you can read a paper published 63 years ago today on lung cancer

In England and Wales the phenomenal increase in the
number of deaths attributed to cancer of the lung provides
one of the most striking changes in the pattern of
mortality recorded by the Registrar-General. For example,
in the quarter of a century between 1922 and 1947 the
annual number of deaths recorded increased from 612 to
9,287, or roughly fifteenfold. This remarkable increase is,
of course, out of all proportion to the increase of population

Some people were arguing that the increase was just due to better diagnosis of lung cancer, and even  those who believed in a real increase weren’t sure of the reason

Two main causes have from time to time been put forward:
(1) a general atmospheric pollution from the exhaust
fumes of cars, from the surface dust of tarred roads, and
from gas-works, industrial plants, and coal fires; and
(2) the smoking of tobacco.

Richard Doll and Austin Bradford Hill decided to compare histories of smoking in lung cancer patients and those in hospital for other reasons. As you know, they found that the lung cancer patients were much more likely to be heavy smokers. It’s also interesting to read what other possibilities they considered, and how they tried to rule them out.

This sort of study isn’t completely definitive, and, famously, the eminent statistician and geneticist (and heavy smoker) R. A. Fisher was never convinced. He thought that genetic factors might well be responsible. Further evidence was provided by experiments in animals (such the ‘smoking beagles‘ of Duke University) showed that smoking really could cause cancer. Also, much more recently, studies of twins and studies that actually measured genotypes showed that genetic differences weren’t a big enough contributor to lung cancer to explain the correlation.

In contrast to, say, alcohol or opium, tobacco has been a public health problem only for about a century: tobacco smoking became very widespread in men during the first world war. With a bit of effort and some luck, future generations might see it as an inexplicable historical anomaly, like a deadly version of canasta.

• Big Data and Due Process: fairly readable academic paper arguing for legal protections against harm done by automated classification (accurate or inaccurate)
• The Herald quotes Maurice Williamson on a drug seizure operation

“The harm prevented from keeping these analogues away from communities has been calculated at $32 million,” Mr Williamson said.

Back in 2008, Russell Brown explained where these numbers come from. As you might expect, there is no reasonable sense in which they are estimates of harm prevented. They don’t measure what communities should care about.

• Levels of statistical evidence are ending up in the US Supreme court. At issue is whether  a press release claiming that a treatment”Reduces Mortality by 70% in Patients with Mild to Moderate Disease” is fraud when the study wasn’t set up to look at mortality and when the reduction wasn’t statistically significant by usual standards.  Since a subsequent trial designed to look at mortality reductions convincingly failed to find them, the conclusion implied by the press release title is untrue, but the legal argument is whether, at the time, it was fraud.
• From New Scientist: is ‘personalised’ medicine actually bad for public health?

The Herald has a story about hazards of coffee. The picture caption says

Men who drink more than four cups a day are 56 per cent more likely to die.

which is obviously not true: deaths, as we’ve observed before, are fixed at one per customer.  The story says

It’s not that people are dying at a rapid rate. But men who drink more than four cups a day are 56 per cent more likely to die and women have double the chance compared with moderate drinkers, according to the The University of Queensland and the University of South Carolina study.

What the study actually reported was rates of death: over an average of 17 years, men who drink more than four cups a day died at about a 21% higher rate, with little evidence of any difference in men.  After they considered only men and women under 55 (which they don’t say was something they had planned to do), and attempted to control for a whole bunch of other factors, the rate increase went to 56% for men, but with a huge amount of uncertainty. Here are their graphs showing the estimate and uncertainty for people under 55 (top panel) and over 55 (bottom panel)

There’s no suggestion of an increase in people over 55, and a lot of uncertainty in people under 55 about how death rates differed by coffee consumption.

In this sort of situation you should ask what else is already known.  This can’t have been the first study to look at death rates for different levels of coffee consumption. Looking at the PubMed research database, one of the first hits is a recent meta-analysis that puts together all the results they could find on this topic.  They report

This meta-analysis provides quantitative evidence that coffee intake is inversely related to all cause and, probably, CVD mortality.

That is, averaging across all 23 studies, death rates were lower in people who drank more coffee, both men and women. It’s just possible that there’s an adverse effect only at very high doses, but the new study isn’t very convincing, because even at lower doses it doesn’t show the decrease in risk that the accumulated data show.

So. The new coffee study has lots of uncertainty. We don’t know how many other ways they tried to chop up the data before they split it at age 55 — because they don’t say. Neither their article nor the press release gave any real information about past research, which turns out to disagree fairly strongly.

From Pharmac’s annual report for 2012 (via @sudhvir), a graph comparing actual government expenditure on subsidised drugs (red) with what would be projected under pre-Pharmac subsidy policies (blue)

This table from the report shows some of how this was done. It shows the twenty drugs on which the most money was spent

Many of these are new (any drug whose name ends in ‘b’ is likely to be new), but they are mostly drugs that are genuinely better, at least for a subset of patients, than the alternatives.  The top of the list, atorvastatin, lowers cholesterol more effectively than the cheaper simvastatin. It’s the best selling drug of all time, but in New Zealand is used only in a relatively small set of  people whose cholesterol doesn’t go down enough on simvastatin. Adalimumab was a breakthrough in serious rheumatoid arthritis, and trastuzumab is the revolutionary breast cancer treatment sold as Herceptin.

Further down the list, candesartan is a blood pressure drug that can be used in people who have side-effects with some other blood pressure drugs. In Australia, candesartan and its relatives are used very widely; here they are used only when other drugs are insufficient or not tolerated.

Pharmac isn’t perfect, and I think it’s underfunded, but it does a very good job of getting most of the benefit of modern pharmaceutical medicine at a very low price.

According to the Herald, the ACC wants us to be careful about weddings — about getting injured at them, that is.

Weddings are supposed to be the happiest day of your life – try telling that to the hundreds of people who make ACC claims for injuries at ceremonies.

From tripping on the bride’s dress to swallowing the ring, nuptials can be surprisingly hazardous.

New figures show at least 600 people made claims to the ACC between 2010 and 2012.

So, how does the 600 claims over three years compare to what you’d expect from an average day?

The ACC accepted 1.7 million new claims last year, which gives about 0.4 claims per person per year, or about 0.001 per person per day.

There were about 20 000 marriages in New Zealand last year, so about 60 000 over 2010-2012, giving about 0.01 ACC claims per marriage.  The 600 reported claims would then be about what you’d expect if there were 10 person-days of exposure per marriage.

My experience is that wedding celebrations typically involve more than ten people, and, with setup and rehearsals, often more than one day.  It looks as though weddings, like Christmas, are actually safer than ordinary days.

An interesting piece in Slate on longevity (via @juhasaarinen).  Unlike the typical story using life expectancy, it’s by someone who seems to understand what it means. There’s also an interactive graph of how causes of death have changed over time, which is notable for having the best use of a creative y-axis scale I’ve seen in a long time.

If you look at ‘influenza and pneumonia’, there is a general decrease with a dramatic spike in 1919. It’s so dramatic that it pops out of the top of the lower panel and spikes into the upper panel. This is the famous Spanish Flu pandemic — the same  rate in today’s New Zealand would mean over 25000 deaths.  Fortunately the three flu pandemics we’ve had since then have all been much less nasty.

It’s also worth noting that nearly all the decline in infections as a major cause of death happened before antibiotics became widely available in the mid-1940s. That’s the reason I’m not really convinced that antibiotic resistances is going to kill us all, though it’s certainly worth avoiding.

The Herald had a story on Tuesday about a UN survey of men in nine areas in Asia/Oceania asking about rape and violence against women.  The story is pretty good, and actually has links to the articles in the medical journal Lancet.

Because of the wide publicity and the large scale of the survey I think it’s worth nailing down some of the details to make it harder to dismiss.  (more…)

The Herald, like many other news sources worldwide, has picked up on a paper in the Proceedings of the National Academy of Sciences. Like the other glamorous top science journals, PNAS publishes some top-level science, and also some that is perhaps not quite up to the standard.

The story says that men with smaller testicles make better fathers, based on a fairly weak correlation in a relatively small sample of new fathers. As Dr Isis points out, this sample only included 9 dads who did more childcare than the mothers.

If you look at the paper (which you can’t, unless you have a subscription), you find that there was a moderately strong relationship between testosterone levels in the blood and the ‘parenting quality’ questionnaire. When the researchers compared men with similar levels of testosterone and similar working hours, there was no correlation between testicle size and parenting, but if testosterone and hours at work were ignored there was fairly weak evidence of a correlation between testicle size and parenting.  (The researchers presented their evidence using p-values, with p=0.08 , not up to usual standards. I think it would be unconvincing with other ways of measuring evidence as well)

The Discussion section of the paper starts out

which is, apparently unintentionally,  a pretty damning criticism.

Oh, the post title? Anyone old and British should be able to explain it

From the Journal of Nutritional Science

Young adult males (n 35) were supplemented with either half or two kiwifruit/d for 6 weeks. Profile of Mood States questionnaires were completed at baseline and following the intervention. No effect on overall mood was observed in the half a kiwifruit/d group; however, a 35 % (P = 0·06) trend towards a decrease in total mood disturbance and a 32 % (P = 0·063) trend towards a decrease in depression were observed in the two kiwifruit/d group. Subgroup analysis indicated that participants with higher baseline mood disturbance exhibited a significant 38 % (P = 0·029) decrease in total mood disturbance, as well as a 38 % (P = 0·048) decrease in fatigue, 31 % (P = 0·024) increase in vigour and a 34 % (P = 0·075) trend towards a decrease in depression, following supplementation with two kiwifruit/d. There was no effect of two kiwifruit/d on the mood scores of participants with lower baseline mood disturbance

From the Otago press release

Eating two kiwifruit a day can improve a person’s mood and give them extra energy, new research from the University of Otago, Christchurch (UOC) shows.

Over a six-week period, normally-healthy young men either ate two kiwifruit a day or half a kiwifruit daily as part of a research study into the potential mood-enhancing effects of the fruit.

Researchers found those eating two kiwifruit daily experienced significantly less fatigue and depression than the other group. They also felt they had more energy. These changes appeared to be related to the optimising of vitamin C intake with the two kiwifruit dose

From the Herald

Eating two kiwifruit a day can improve mood and energy levels, a new University of Otago study shows.

Those eating two kiwifruit were found to experience significantly less fatigue and depression than the others. They also felt they had more energy.

I’m not criticizing the research, which was a perfectly reasonable designed experiment, but if the findings are newsworthy, they are also worth presenting accurately.