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What Do Scientific Studies Show?

May 13, 2013

As any regular reader of news will know, popular media report “scientific results” nearly every day. They come delivered in news reports and opinion pieces, and are often used to make a variety of points concerning important matters like health, parenting, education, even spirituality and self-knowledge. How seriously should we take them?

For example, since at least 2004, we have been reading about studies showing that “vitamin D may prevent arthritis.” A 2010 Johns Hopkins Health Alert announced, “During the past decade, there’s been an explosion of research suggesting that vitamin D plays a significant role in joint health and that low levels may be a risk factor for rheumatologic conditions such as rheumatoid arthritis and osteoarthritis.” However, in February 2013, a more rigorous study called the previous studies into serious question. Similarly, despite many studies suggesting that taking niacin to increase “good cholesterol” would decrease heart attacks, a more rigorous study showed the niacin to have no effect.

Such reports have led many readers to question the reliability of science. And given the way the news is often reported, they seem to have a point. What use are scientific results if they are so frequently reversed? But the problem is typically not with the science but with the reporting.

In both the above examples, earlier studies had shown a correlation but not a causal connection. They had not shown that, for example, taking vitamin D was the only relevant difference between those whose pain decreased and those whose pain did not decrease. Perhaps, for example, those taking vitamin D also exercised more, and this was the cause of the pain decrease. Typically, the best way to establish a cause rather than a correlation is to perform a randomized controlled experiment (R.C.T.), where we know that only one possibly relevant factor distinguishes the two groups. In both the vitamin D and the niacin cases, there was an R.C.T. that showed that the earlier results had been merely correlations.

Excerpt from an article written by GARY GUTTING at NYT. Continue THERE

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