Cognitive decline research: Questions the CBC didn't ask

Today's CBC news report (click here) of a study of cognitive decline is pretty standard science reporting. I'm sure that other news sources provided much the same story. Anyway, it confines itself to reporting the results the researchers reported, results which were fairly stated.

However, there is other information the CBC might have provided, but didn't. First, it doesn't provide a link to the study (or hadn't when I posted a comment asking for one). I, for one, was interested in learning what "a 3.6% decline in mental reasoning" was. Does a decline of that size have a serious effect on people's functioning?

So I looked for the link and found it (here). It's an open access article that can be downloaded free in a PDF. The article doesn't provide a quick answer to the question of how serious the declines observed are, but the authors do suggest that further attention might be paid to people whose declines are greater than the mean in the study. That suggests to me the mean declines are not that serious, although I readily admit I may be reading something into the authors' suggestion that isn't there.

What I also found, though, is that the researchers did not control for health. Since older people tend to be less healthy, were these cognitive declines due to changes in brain function or to the fatigue resulting from poor health? Information about medical risk factors was collected, but the article does not report that it was incorporated in the statistical analyses.

None of this is intended to question the adequacy of the research. Being able to carry on a rigorous study of over 10,000 people for 24 years is proof enough of the researchers' competence. What this is intended to question is the value of a news report that simply reports results without examining them. I'm sure that if the researchers had been asked about the relationship of the health information they collected to cognitive decline they could have explained it fully. I'm sure if they'd been asking questions like that the journalists would have enjoyed their jobs more, too.