SciBlogs

Archive July 2012

Hair trumps helmet John Pickering Jul 21

Christchurch city councilor and Canterbury Health Board member Aaron Keown is on another crusade.  This time he wants the bicycle helmet law repealed because “Putting a lid on your head messes up your hair, and for a lot of people that is an issue,”  (see here ).
“Vanity, vanity, everything is vanity”
and that should be the end of it, if he wasn’t serious.  He is.  He thinks the look of a helmet and the cost is stopping Christchurch become the Amsterdam of the South Pacific.  Having lived and worked in Amsterdam, I can think of many reasons, not least being driver behavior, why we won’t emulate that city. As for being put off cycling, nothing is morre disturbing than having fat bottomed cyclist zooming past you on the cycle path in skin tight lycra.  Ban lycra I say…thousands more will dust off the old treadly and all will be well.
Having said all that, Mark #18, commenting on the Press web said states “Aaron Keown has some good science to support his case: http://www.cyclinghealth.org.nz/ But never let science and logic get in the way of so-called “common sense” – especially when “common sense” is supported by anecdotes.”   OK then, let’s see what that “good science” is.  The web page quoted has No science whatsoever on it.  It links to one and one only paper from a science journal, namely the NZ Medical Journal of February 2012 . That sounds promising, so let us look at that article. I regularly get to referee articles for inclusion in medical journals, so I shall apply the same scrutiny to this one.
Evaluation of New Zealand’s bicycle helmet law
Colin F Clarke
NZMJ 10 February 2012, Vol 125 No 1349
The first thing that strikes me is that it is an “evaluation” rather than trial or systemic review.  That is, it is some word of (expert) opinion.  Fine, journals have those kinds of articles all the time.  They are worth reading if the person writing them really has expertise (see the end of the article and judge for yourself if Colin Clarke is really expert or not). They should not be talked about, though, in the same breath as a clinical trial or systemic review or metaanalysis.
The second thing that strikes me as I read through is that is is full of numbers used to support the author’s opinions, but there are no statistics at all to back this up.  My PhD students would get a flea in the ear if they tried to present a differrence in means to me as meaningful without backing it up by the appropriate statistical test which tells me how likely the difference is to be real rather than random variation.  I would not agree to publication of any article that looks at relative risk, as Colin Clarke does without presenting 95% confidence intervals so that I could see if a relative risk of, say, 2.4 was really differnt from 1.  ie was the risk of death by cycling really 2.4 times that of walking? If the 95% confidence interval straddles zero (eg 95%CI -0.6 to 5.4) then the answer is “probably not.” Without that information,
“Meaningless, meaningless, everything is meaningless.”
Mr Clarke’s conclusions are just that. Furthermore, he makes the mistake of assuming that changes in incidences of death or injury since the advent of the helmet are because of the helmet.  He does not account for other changes including the lightness and speed of bikes, the greater density of cars on NZ roads etc etc etc.
Sorry Mark #18, this is defininetly NOT good scientific evidence.  As a scientists in a university Department of Medicine in New Zealand, I am ashamed that the NZ Medical Journal should allow such poor science to be published.
I am aware there is some research on the issue in other jurisdictions.  It is not so overwhelming as to have resulted in comissioned studies in NZ, let alone a change of law. Certainly vanity is not a reason to trump safety.  In the meantime, Cr Keown, I expect better of someone on the CDHB health board.  We have many issues on this city that are much more important. Drop this one and get on with your job

Tagged: bicycle, helmet, Risk

Fat Rulz OK! John Pickering Jul 13

Dr Cat Pause is a Fat advocate.  For her “Obese” is a negative term, but Fat is good. She hit the headlines this week as the organiser of New Zealand’s first Fat Studies conference.  Listening to her interviews (see eg TVNZ interview) and reading some media around this event I detect two strains of argument

1. Fat people are discriminated against, therefore they need legal protection and a culture change in society.

2. Being Fat is not the detriment to health that most people think it is.

Regarding point 1, the language and emotion appear similar to other arguments from groups who believe they are discriminated against.  Over the last 40 years there has been tremendous change in NZ law to ensure no New Zealander is discriminated against on the basis of sex, sexual orientation, or race.  I thought the laws were broad enough to encompass other forms of discrimination including body size.  Apparently not according to Dr Pause.  Whether there is need for change is a matter for sociologists, psychologists, lawyers, politicians and anyone else who is interested to thrash out.  In the meantime I and most people I know would be happy to declare that it is absolutely wrong to put down someone simply because of their size; as Dr Pause said “Fat people deserve the same rights and dignity as non-Fat people.

It is the second claim of Dr Pause that which gives me some concern.  In a TVNZ interview she stated that science is not clear-cut about the relationship between fat and health.  When pushed on this claim she talked of studies linking weight and death: “quite often what we find is that studies will look at people who die and if anyone is fat in that sample they will say they died because of their weight.”  Frankly, I too would dismiss to the trashcan any studies that did this – that is bad science.  However, I don’t believe most studies do do this.  Rather they look at the rates of death and find that the rates are increased in the group with higher body mass.  That is, they are simply reporting an association rather than describing a cause.  Could her passion for fairness and justice be clouding her objectivity? Possibly. I see that in statements like “Fat people live in a world that openly hates them. They talk about solving the obesity epidemic.  That means getting rid of people like me.” Really?  I hope no one wants to get rid of you Dr Pause.  I expect many medical professionals are uneasy that her size may contribute negatively to her health – it is only part of her that they want to be rid of.

Could there be, though, something in the science throwing doubt on the claims that Fat is bad? The answer  is “yes, of course.”. Some call this the “Obesity Paradox.” Such is the nature of statistics and physiology that there are many exceptions to the rule that Fat is bad.  In a paper “Weight Science: Evaluating the Evidence for a Paradigm Shift (thanks David from The Atavatism blog for pointing this out) many of these exceptions are discussed.  The paper unfortunately seems to fall in the gap between being a meta-analysis and review, and perhaps fails to do justice to both genre.  Nevertheless, it raises several issues which throw doubt on the simplistic “all fat is bad” approach.  The authors claim that the, now common, belief that the current generation of children will live shorter lives than their parents because of obesity comes from an “opinion piece” in the New England Journal of Medicine which offered “no statistical evidence” to back it up (Full text here).  Good point, if true.  Looking at the NEJM article, though, statistics and a mathematical model for predicting life expectancy which takes into account obesity were used.  The conclusion was:

Our conservative estimate is that life expectancy at birth in the United States would be higher by 0.33 to 0.93 year for white males, 0.30 to 0.81 year for white females, 0.30 to 1.08 years for black males, and 0.21 to 0.73 year for black females if obesity did not exist (Figure 1). Assuming that current rates of death associated with obesity remain constant in this century, the overall negative effect of obesity on life expectancy in the United States is a reduction in life expectancy of one third to three fourths of a year.”

That there are many fat people who live long lives should not surprise us.  When people were arguing about smoking, every second smoker seemed to have an aunt who smoked a pack a day yet lived to 90.  Statistics are like that.  That fat may be protective in some circumstances should also not be surprising.  Diseases are a complex and full of surprises.  Having said that a brief look at the article in question showed me that it was disingenuous – it suggested that in a number of diseases obese people had greater longevity than thinner people.  I looked at the reference given for type II diabetes (see here) and found the abstracted stated that “Diabetic men and women of average weight had the lowest mortality. A J-shaped relative risk curve by weight category was found, with a poorer survival rate for those who were thin, overweight, or obese.”  Hmmm….not the impression given by the authors advocating a paradigm shift in thinking about obesity.  That paper is worth a read, but be cautious.

Unexplained findings should drive us to gain a better understanding of the disease processes and ultimately help us to deliver better health care.  I am less convinced that they should be used as a rallying cry by advocates for being Fat and Healthy.  Health is a relative term and there is no doubt that some Fat people are healthier than some non-fat people, but this does not mean they are as healthy as they can be.  Dr Pause calls for “not using weight as a proxy when talking about health.”  When faced with an individual I would expect a doctor to look at my health first, and my risk factors second.  Someone’s weight (very low or very high) may well be a risk factor for a disease…talking about it is not using it as a proxy.  Referring to statistics that test if weight is a contributing factor to a disease or poor outcome is no more using fat as a proxy as using ethnicity or sex or a comorbidity as a proxy.  They are simply risk factors which may be contributing to a disease process in an individual – they are flags for a doctor to carry out tests to eliminate or confirm the presence of certain diseases…without them the health system would either do nothing or crumble under the weight of “testing everyone for everything.”

In my own field of Acute Kidney Injury two recent epidemiological studies have shown that obesity is a risk factor for they disease after accounting for other factors (1,2). What is surprising, though, is in one study (note to reader…always take the epidemiology of just one study with a dose of caution) looking at patients with Acute Respiratory Distress Syndrome (ARDS) the body mass index was associated with decreased mortality.  However, AKI remained associated with increased mortality even after adjusting for body mass index.  I hope this kind of science will lead to further discovery of what may be protective measures in obese people with ARDS and be able to artificially apply those measures to all people.  This seems a better approach than taking one study like this and only one outcome from it (albeit an important one) and using it to say “Fat is OK.”

Dr Pause and her colleagues are advocating for a health centric rather than obese centric approach.  Seems sensible to me.  I would imagine that is exactly why most medical professionals do when they point out that some of someone’s health problems are due to their weight. What is becoming apparent, and may require changes in medical practice, is that the process of losing weight may be detrimental to health.  This is based on the theory that toxins stored in fat tissue are released when someone looses weight.  The rate of weight loss may be relevant here and whether is is kept off (a rare occurance apparently).  As it is the kidneys deal with toxins I’d like to see if dieting is a risk factor for Chronic Kidney Disease (obesity is).  Certainly, looking at the effects of dieting on health is a worthwhile research topic.  However, this begs the question – why store those toxins in the first place!  In the process of getting fat what damage has been done though the ingestion of large volumes of sugars? Is feeding our children poor nutrition resulting in some of them getting fat acceptable under any circumstance?  I think not.

Dr Pause appears to me to be in danger of cheery picking the science to support her social and political campaign.  Her statement that the “science is on her side” raised my “warning” antennae. It is the language of “me” verse “them” which I find distinctly unhelpful knowing that there are many scientists who will say “no it’s not.”  That some are prepared to challenge conventional wisdom in medicine is a good thing.  That they are prepared to use science to do so is even better.  However, it is beholden on all scientists to maintain objectivity .  This is not always easy and no doubt much harder when one feels discriminated against.

Tagged: Acute Kidney Injury, Fat, health, Obesity

Kidney Attack John Pickering Jul 09

It has the same incidence as heart attack, 3,000,000 will die of it this year, yet no one has heard of it.  What is it?  Hopefully, the post title gave you a clue.  Kidney Attack is the latest in a long list of names for the disease I study (I’ve been calling it Acute Kidney Injury in this blog). This last week I was in Sydney where I conducted a seminar for Nephrologists and Intensivists – I’d recently been reading an article (referenced in the image below) and decided that the history of the nomenclature was a good place to start my presentation.  This resulted in the info graphic below which I have also posted on my specialist AKI blog over at www.gkaonlineacademy.com/blog, however for fun I thought I’d post here as well.  What struck me when putting this together is that it took about 1800 years from Galen’s first written description in the second century until the first consensus definition was arrived at in 2004.  Since then there have been two more definitions (iterations of the first) and more to come. Two reasons for this: first is that the recognition that even a mild form of AKI increases the risk of premature death, and second that proteomics and genomics have identified a plethora of new new biomarkers of structural injury to the kidney.  It is my job to help figure out what to do with them.

Kidney Attack- the evolution of a name

Kidney Attack- the evolution of a name

Tagged: Acute Kidney Injury, health, Kidney Attack, minfos

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