Archive for September, 2010

Sep 07 2010

Organic Food Quality

Published by under General Science

In my perfect world major societal decisions would be based upon logic and evidence, not ideology. But humans are ideological creatures – we develop belief systems that we jealously defend, and are subject to confirmation bias so that we falsely believe the evidence supports our ideology.

For example, I have never been a fan of organic farming. I have nothing specific against it, however it seems to me that the increasing popularity of organic farming is based largely on ideology (a naturalistic fallacy) than on evidence. I have no dog in that hunt, as they say – no vested interest in organic vs conventional farming at all. I really cannot think of a reason why I would care one way or the other – I simply want what works. Whatever farming methods are the most efficient and sustainable, producing the highest quality and cost-effective food – that’s what I support.

Organic farming is an odd mix of beliefs that are historically based upon the vague notion that “natural” is better. That does not mean that some good ideas have not emerged from the culture of organic farming, and I think if it has anything to offer it is a strong advocacy of sustainable farming. But when I listen to advocates, either personally or in a public forum, they seem to focus on a few specific claims that are rather dubious. I hear a lot about the evils of “big agro” and how organic farming supports small local farmers. However, if you buy organic at your supermarket you are likely buying from a “big agro” company that likes the higher profit margins of organic produce.

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104 responses so far

Sep 03 2010

Dementia and Mental Activity

Published by under Neuroscience

With our aging population diseases and disorders that increase dramatically with age are of special concern. Among such disorders is dementia, the most common cause of which is Alzheimer’s disease. There has been a suggestion in the research that increased mental activity decreases the risk of developing dementia, or at least delays its onset. It certainly would be nice if playing sudoku could stave off dementia – that is a fairly risk-free intervention and it may actually reduce the burden of a terrible and costly disease on society. But the research, while highly suggestive of a protective effect, is not yet definitive.

A new study published in the September issue of the online version of Neurology, adds to the research and follows subjects for longer than previous studies (11 years on average). They found that mental activity does delay the onset of dementia, but when they continued to follow subjects they also found that mental activity increases the rate of progression of dementia once it starts:

On clinical evaluation, 614 people had no cognitive impairment, 395 had mild cognitive impairment, and 148 had AD. During follow-up, the annual rate of global cognitive decline in persons without cognitive impairment was reduced by 52% (estimate = 0.029, SE = 0.010, p = 0.003) for each additional point on the cognitive activity scale. In the mild cognitive impairment group, cognitive decline rate was unrelated to cognitive activity (estimate = -0.019, SE = 0.018, p = 0.300). In AD, the mean rate of decline per year increased by 42% (estimate = 0.075, SE = 0.021, p < 0.001) for each point on the cognitive activity scale.

This is a very interesting result. If true, it means that mental activity would tend to compress the duration of dementia – delaying onset but then hastening progression, so individuals would spend less time in a demented state.

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8 responses so far

Sep 02 2010

Alcohol and Survival

An interesting controversy that has simmered in the medical literature for years is the effect on health and survival of moderate alcohol consumption. Epidemiological studies consistently show that moderate drinkers live longer than abstainers, while heavy drinkers fair the worst. Before we discuss possible mechanisms for this effect, we have to consider whether or not the effect is real – and here controversy remains.

One of the reasons for the controversy is that the data supporting a protective effect of moderate alcohol is all observational, rather than experimental. It is simply not possible to do a study in which subjects are randomly assigned to either no, moderate, or heavy alcohol consumption (especially in a blinded fashion). Therefore researchers must be content with mere correlation. This is useful but very problematic evidence.

The weakness of observational evidence like this is confounding factors. Since people self-select their own alcohol consumption there may be many other lifestyle choices that go along with that and affect health and survival. There may even be genetic types that lead people to drink and also confer greater longevity. Without randomization the possible confounding factors are enormous. Continue Reading »

29 responses so far

Sep 01 2010

Appeals Court Rejects Autism-Vaccine Link

This is a quick update on the Autism Omnibus hearings – representative cases heard before a special court to decide if there is any credible evidence to conclude that autism may be a vaccine injury. After hearing exhaustive testimony by all sides, the special masters determined that the evidence does not support a link between autism and vaccines.

One of the cases heard was the Cedillo case, which was used as the test case for the theory that the MMR vaccine plus exposure to thimerosal can trigger brain damage that looks clinically like autism. In February of 2009 the court rejected the claim that Michelle Cedillo’s autism was caused by vaccines. No only was the theory of causation without scientific backing, evidence was presented to show that Michelle Cedillo demonstrated early symptoms of autism prior to ever receiving the MMR vaccine.

In fact the Cedillo case is representative of a fact that scientific research is increasingly demonstrating – that subtle signs of autism are present prior to parents noticing that there is a problem and long before formal diagnosis. The consensus of evidence is that signs of autism appear between 6-12 months of age, and maybe earlier in some cases. Meanwhile, the first MMR vaccine is given at 12 months. Since causes must precede effects, this fact alone is fatal to the MMR-autism hypothesis.

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26 responses so far

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