http://www.healthnewsreview.org/2013...lways-so-well/

excerpt:
The words matter. Accuracy matters. I shouldn’t have to tell the New York Times that. But read some of the comments left online by readers of the “Some Fruits Are Better Than Others” piece. Readers are telling the Times to get with it as well. Excerpts of those comments:

Type 2 diabetes is to a large degree a disease of poor people. So any factor that is related to socioeconomic status will correlate to lower diabetes risk, because wealthier, more highly educated people tend to have a lower diabetes risk.Blueberries are probably a good surrogate for wealth/education. If you can afford $5 a pint for blueberries twice a week, you probably have a higher income and education level and less chance of coming down with diabetes.The exact same correlation would be found for French wine, truffles, and good balsamic vinegar.Likewise, you can “reduce your diabetes risk” by buying Fendi purses, Ferraris and first-class airline tickets.
Anyone who buys blueberries five times a week would probably have an intense interest in health & probably not be rounding out their diet at McDonalds the rest of the week.I doubt blueberries cause reduction in diabetes. They are just proof that having access to fresh produce you can afford, year-round, will keep you healthier. I’m not sure that’s news.
As my Statistics professor tried to drum into our heads:“Correlation is not causation!”
These comments are very helpful. It is a new journalistic phenomenon that the NYTimes comments contain as much wisdom as the original articles.
This was a poorly written article that created more questions than it answered.
I wish these articles would always put a disclaimer that studies like these do not prove causation or prevention.

"with this, therefore because of this"

Probably the most common mistake in the diagnosis and treatment of medical and psychological conditions. Actually, probably the most common mistake in general when analyzing correlated variables.

You are both correct: correlation does not imply causation.

But, it seems to me, rather unsatisfactory to leave it there.

In life we have to continually make decisions: do we do this exercise or that, do we take a particular supplement or not, do we start to take levodopa now or not. Often there is little or no data to help us make our decision. Often we are forced by circumstances to make a decision now.

In these situations we are forced to rely on experience (often barely relevant) and whatever data we may find (often poor quality).

With this in mind, let's look at the blueberry example mentioned in the article. I agree the evidence in favour of the blueberry is weak: the positive correlation is likely to be due to confounding issues. But, since the confounding argument is not certain to be correct, the evidence in favour of them is still positive.

Put another way, on the evidence presented in the article, and ignoring cost, is there a better course of action?

John

Eating my blueberries, coconut oil and oatmeal topped with kefir as I read this!

there have been some small studies showing blueberries hellp improve memory in humans so i don't think blueberries are a great example. the article is food for thought, the internet allows a lot of junk to get disseminated.

Love my berries, blue, black or red. Have to agree, berries with coconut oil and oatmeal tastes great (haven't tried the kefir)!

John, the problem is really one of the media. They love to highlight and promote research findings when they find correlated items without properly disclosing that there may in-fact be no direct or indirect causation. As a matter of fact, many of the studies clearly point out the inability to determine if there is any causation and the media just overlooks that point.
Unfortunately, you can't ignore cost and many times there may be better course of action, or inaction. Too many people act on correlated studies only to find out later that there is no actual direct casual relationship.

Making a decision on correlated variables that appear to be logical doesn't always turn out to be correct. Unfortunately, our intuition can lead us astray when it comes to distinguishing between causality and correlation. For example, there have been many studies showing that not eating breakfast is strongly correlated with poor performance in elementary school. It would be easy to conclude that eating breakfast causes students to be smarter. However, when actual controlled studies were done, eating breakfast did not cause higher grades. It turns out that not eating breakfast was also correlated with two other variables, absences and tardiness, which were the actual causes of the lower performance.

In general, we should all be wary of our own bias; we like explanations. The media often concludes a causal relationship among correlated observances when causality was not even considered by the study itself. Without clear reasons to accept causality, we should only accept correlation. Two events occurring in close proximity does not imply that one caused the other, even if it seems to makes perfect sense.

Tupelo3, I agree with every word you write bar one, the word "too" as in:
"Too many people act on correlated studies ..."

The word "too" implies a comparison with some available alternative, as in the sentence: "Too many people drowned when the ship sank because the lifeboats were locked." The problem for PwP is that there are no lifeboats that will take us to safety, though there are plenty of lifejackets that stop us from drowning for a long time.

I am reminded of a story, it may be apocryphal, about a mountaineer climbing in the Himalayas. When night arrived he found himself above 8000 metres. He reckoned that at this altitude and with such low temperatures he would probably die if he stayed here. He noticed that an icy slope led down to his camp. Unfortunately, this slope was too steep to climb down. He could slide down it, but he might hit rocks before he got to the bottom, which would surely kill him. What would you do if you were in his predicament?

The point I'm making is that in some circumstances making a decision on the basis of partial information is rational.

This is not to say that every factor correlated to Parkinson's should be explored willy nilly. At the least, there should be a high expectation that the therapy is safe and does no harm. As far as I know, this is the case with blueberries.

The challenge comes in trying to combine weak statistical data with weak causal data in an as effective a way as possible.

John