SciBlogs

Archive September 2012

Children killed by mothers – duh! John Pickering Sep 25

The media is in a tiz over a police report stating that 45% of children killed in family violence were killed by their mothers.  The Herald says “Children are far more likely to be killed by their mothers than any other category of offender,”; Newstalk ZB reports Bob McCoskrie as saying this is “startling”; Stuff ramp it up a bit and begin “Nearly 50 per cent of children who die as a result of family violence are killed by their mothers.”

Well, duh!  Don’t they know that children are far more likely to be living with their mothers than any other adult?  The “any other category of offender” the Herald talks about include Fathers, Stepfathers, Boyfriends, Grandmothers, and various others.  Given there were 33 deaths looked at this is a large number of groups to try and analyse.  For the numbers to have any meaning they need to assess the numbers using what are called “case controls.” For example, if they looked at other factors, eg socio-economic, and then assessed the make up of households in that group they may find that children in that group are living predominantly with their mothers and much less with Fathers, Stepfathers, boyfriends etc.  The numbers may only reflect who they are living with, not some kind of “evil mother” syndrome.

What use, really is such a report?  How will it help prevent further deaths?  I suspect the answers are “little” and “it won’t” but this will not prevent endless ours of hand wringing in the media.  Surely, we can do better.

Tagged: children, family violence, Mothers, Murder, Statistics

Vitamin D: “Silver bullet or fool’s gold?” John Pickering Sep 21

Vitamin D has had big raps lately.  We know that low levels of it correlate with higher levels of some diseases, but does taking a supplement help?  An article in the Herald this morning by Martin Johnson nicely outlines a study  being undertaken by Professor Robert Scragg of the University of Auckland.  His is the quote in the title.

Why is there need for an expensive trial when lots of observation studies show low levels of Vit D mean you are more likely to get Cardiovascular (and other) diseases, high levels mean you are less likely?  Isn’t it obvious that by taking supplements that health outcomes will improve?  Sadly, no it isn’t.  Correlation does not mean causation (or “Post hoc ergo propter hoc” for you latinistas out there – I learnt this from a re-run of West Wing this week).  What this means is that there is more than one reason for the correlation ie:

  1.  Illnesses are because Vit D is an essential component in the biochemical pathway’s that provide a defense against these illnesses (causation), or
  2.  Low Vit D is a consequence of something else that has gone wrong that also causes the diseases (ie Vit D is a “flag” or “marker” for something else).

If 1 is true, then raising Vit D levels may help.  If 2 is true, then raising levels probably won’t help.  For the moment assume 1 is true, then the next question is “does supplementation help?”  Again, most would think “Of course.”  However, it is possible that by bypassing the mechanism by which the body makes its own Vit D (ie beginning with exposure to the sun) the body’s response to the increased Vit D is different.  These, and others, are reasons why a Randomised Controled Trial (RCT) in which some participants get Vit D and some get Placebo (in this case sunflower lecithin) is conducted.  There is some information about the trial in the Herald article, more can be found on the Aust NZ Clinical Trials Registry here.  Briefly, participants (50 to 84 years of age) will receive 1 capsule a month for 4 years.  The incidence rate of fatal and non-fatal cardiovascular disease is the primary outcome. Secondary outcomes include the incidence of respiratory disease and fractures. They need to recruit 5100 people (so get involved!).

Why so many people?  This is because they want to avoid making two mistakes.  They want to know with high certainty that if they see a difference in the rates of cardiovascular disease between the Vit D and Placebo group, the that it is not a difference that occurred randomly (ie seeing a difference when there really is no difference).  It is most common to accept a 5% chance of seeing a difference by chance (tossing 4 heads in a row is about a 6% chance).  The second mistake is if the trial were to show no difference between the groups, but for this to be a false conclusion (ie not seeing a difference when there really is a difference).  It is common to accept about a 10% chance of this happening.  Notice, I have talked about “difference” not Vit D being “better” than placebo.  This is very important, because it is possible that Vit D is worse and scientists must take into account that possibility.  That is why scientists also start with what we call the “null hypothesis” – the presumption, in this case, that there is “no difference” in the rates of cardiovascular disease between those taking Vit D and those taking placebo.

I liked the quote of Prof Scragg in the Herald:

“GPs are very supportive of it and I know they are prescribing it extensively to patients. Hospital specialists are sceptical. Me, I’m in the middle. My heart says I want it to work. My head says I have to keep an open mind.”

I too often find myself in the “middle” – hoping with my heart that something works for the good of all, but working with my head so that we don’t end up peddling false hope or worse.

Tagged: Cardiovascular disease, fractures, health, medicine, observation studies, placebo, Randomised controlled trial, RCT, Respiratory disease, Vitamin D

One third of New Zealanders addicted to food: fact or fiction? John Pickering Sep 20

Today’s Press Headlines read “Third of Kiwis ‘need to kick food addiction’”

The quote is attributed to Professor Doug Sellman, Director of the National Addiction Centre and is a call for more funding to support this group. My first reaction was “Give someone a hammer and everything looks like a nail.” Alas, I can’t leave it with my prejudices.

What evidence is there for food addiction and for 1/3rd of NZ’ers being addicted?

I searched the medical literature (PubMed) for any work relating to New Zealand and Food Addiction. I found one article from the NZ Medical Journal co-authored by Professor Sellman: Addictive overeating: lessons learned from medical students’ perceptions of Overeaters Anonymous. (N Z Med J. 2010 Mar 19;123(1311):15-21.). The research is a synthesis of the reports of 72 5th-year medical students who as part of their training attended a meeting of Overeaters Anonymous. The “results” are a series of quotations which pick up on some themes and includes the concept of the attendees talking about the concept of addiction.

A brief look at the review literature on PubMed revealed that the concept of “food addiction” is new and by no means an established addiction. One paper, How Prevalent is “Food Addiction”?  (Front Psychiatry. 2011; 2: 61), talks about how few tools there are to assess food addiction. One tool – a questionnaire –(the Yale Food Addiction Scale) has recently undergone some validation studies. In normal weight participants food addiction, according to this scale, was diagnosed in 8.8 and 11.4%. In one study of obese participants it was 25%. Interestingly there was very little correlation between diagnosis of food addiction and Body Mass Index in these studies. A second freely available review asks the question “Does Food Addiction Really Exist?” (Obesity Facts 2012 19;5(2):165-179). The authors note that in some individuals the underproduction of the hormone, leptin, “has a pronounced effect on the reward system, thus suggesting an indirect link between overeating and ‘chemical’ addiction.” Their major conclusions are:

“Because of the current rather limited evidence of the addictive behavior of specific food ingredients or additives, we currently conclude that food addiction can best be classified as a behavioral addiction at this time. However, because there is not sufficient (i.e., reliable and valid) data on its diagnostic criteria, we would not recommend adding ‘food addiction’ as a diagnostic entity in DSM-V” (the 5th edition of the American Psychiatric Society’s Diagnostic and Statistical Manual of Mental Disorders).

“We conclude that overeating may be viewed as food addiction in a small subgroup of obese individuals”.

Disclaimer: I have no expertise in Psychiatry or eating disorders.

Claimer: I can’t find any published research to support the contention that 1/3rd of New Zealanders are addicted to food.

Tagged: diabets, Food, Food addiction, health, mental-health, Obesity

How can donor rates be increased? : guest post John Pickering Sep 17

I read the following in Kidney Health New Zealand’s annual report and with KHNZ and Paula Martin’s permission I have reproduced her great report.  I am thrilled to see such important research being undertaken and as you’ll read, Paula has great motivation.  Paula is a PhD Candidate in the Health Services Research Centre, School of Government, Victoria University, Wellington, New Zealand.

Kidney Health New Zealand Research Grant

Paula Martin

In 2006 I donated a kidney to my husband. At the time, I was just focusing on getting through the year long donor work up and supporting my husband while we coped with the impacts on our lives of him being on peritoneal dialysis. Only after the transplant did I realise just how few living donor transplants are done each year in New Zealand. In 2006, only 46 other live donors gave a kidney to someone; last year the number had climbed to 57 live donors, but the number of people needing a transplant had also increased dramatically, with around 600 on the official waiting list.

What could be done to increase the current rate of kidney donations? The low number of transplants is a concern because we know that for most people with end stage renal failure, a transplant is the best treatment. In addition, it is cheaper than keeping people on dialysis. In order to develop solutions, we needed research to tell us what the barriers to living donor kidney transplantation are in New Zealand; how similar to, or different from, barriers in other countries these are; and what people involved in the renal community here think could be done about those barriers, so that more people wanting a transplant can get one.

In 2010, I decided to do some research on this topic to fill this gap. Supported by a research grant from Kidney Health New Zealand, I’m currently undertaking a PhD in Public Policy based at the Health Services Research Centre in the School of Government, at Victoria University of Wellington. My focus is solely on living donation, not deceased. Around half of all kidney transplants now come from living donors and with the increasing demand for kidney transplants and the shortage of deceased donors, living transplantation has to be a critical part of solving the problem. The barriers to living donation and deceased donation are different so it’s important to think about them separately.

We know from overseas research that there can be many different barriers: for example, patients needing a transplant often find it difficult to approach their family and friends about whether they might consider living donation; people who want to be donors can face practical barriers such as loss of income while they take time off to recover from the surgery; and many people who would like to be donors discover that they aren’t compatible with the person they want to donate to, or that they have a medical problem of their own which makes them unsuitable. A particular problem in NZ is that Maori and Pacific people often find it harder to get a transplant than European/Pakeha. There are likely to be many different reasons for this. Cultural attitudes to organ donation may be one factor, but a bigger issue may be that it can be harder for these patients to find a donor who meets the strict medical suitability criteria because of things like the high rates of Type II diabetes in these populations.

There is no single solution to this problem – this is an extremely complex issue and we’ll need a variety of different initiatives to make a difference to it. So, I’ve been looking at our legislation and current policies as well as how renal services operate on the ground, and talking to a range of different people – patients, renal specialists, transplant coordinators, patient support groups, managers in District Health Boards and senior government officials and politicians – to find out what they think the issues are.

Finding out what the issues are from a patient perspective has been a big part of the research. With the assistance of the three renal transplant units, I carried out a postal survey last year of all the people on the kidney transplant waiting list and received nearly 200 replies. I’ve followed that up with a small number of in-depth patient interviews. The early results of this part of the research suggest that, as in other countries, patients find it very difficult to “ask” someone to be a kidney donor which often stops them talking to their family and friends about living donation. Furthermore, patients that do get offers from people to be kidney donors often find they are incompatible or the potential donor is medically unsuitable for some reason. Health professionals I’ve interviewed have provided valuable insights into what the issues are from their perspective inside the health system.

I’m aiming to finish this research in 2013. I hope it will be of use to practitioners, policy makers, patient groups and anyone else interested in making a difference to this problem.

Thanks to Kidney Health New Zealand for supporting this work with a grant towards the costs of doing research.

Tagged: Chronic Kidney Disease, Diabetes, Dialysis, health, Kidney donors, medicine, victoria university of wellington

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