Before continuing with my favorite topic - media misinterpretation of health news - I would like to acknowledge something that came up in my class last week: the journalists writing about this stuff do not have it easy. Often they must take something exceedingly complex, decipher it, then translate it into the language of a much lower reading level - all without exceeding a certain word count. Yipes!
The purpose of these comparisons - media vs. scientific journal - is not simply to diss the media. The point is to demonstrate why health professionals should not consider the media a reliable source of health research news. Even when the information reported by the media is accurate, it is often not complete. Simple as that. Sometimes what is left out can make a big difference. I am sure I won't cover everything either - there's nothing like reading the original work!
Anyway, on with the comparison:
NY Times blurb - Exercise: In Women, Training for a Sharper Mind
Liu-Ambrose, T. et al. (2010) Resistance Training and Executive Functions, A 12-Month Randomized Controlled Trial. Archives of Internal Medicine, 170(2):170-178
This was a randomized, controlled, single-blinded, prospective study. 155 women between the ages of 65-75 were randomly assigned to one of 3 groups: resistance training once per week (RTx1), resistance training twice per week (RTx2) and a balance and toning group (BAT). This was reported accurately in the NY Times, except for missing the frequency of the BAT group (they met twice a week).
Details not included: the trial was completed form May 1, 2007 through April 30, 2008. The women were free living (i.e. not institutionalized) individuals from Vancouver, average height, weight, education level, score on visual acuity tests ( > 20/40) and score on the MiniMental State Exam ( > 24). [We debated the meaning of this last score. One classmate said that a score below 30 indicates cognitive decline - so are we to assume that the women in this study may be experiencing some (but not severe) cognitive decline? This would make sense, but is not clear - more info is needed.]
On 3 occasions, the women were put through a series of tests designed to assess executive function: beginning of the trial, midpoint (6 months) and trial completion (12 months). This included the Stroop test (assessment of selective attention and conflict resolution) as well as tests of set shifting and working memory. The tests were described in detail and are quite interesting (i wonder how i would score if someone asked me to name the color of the word "blue" printed in red ink, etc.)
The NY Times states, "improvements in the strength training group included an enhanced ability to make decisions, resolve conflicts and focus on subjects without being distracted by competing stimuli."Ok, well at least the last two were correct ("resolve conflicts" = conflict resolution; "focus on subjects without being distracted by competing stimuli" = selective attention), but the ability to make decisions was not tested. I am not sure where that came from. Also tested (but not reported in the Times) were: gait speed, muscular function and whole-brain volume.
Some other important findings not reported in the Times: after 6 months (at the midpoint evaluation), there were no differences between any of the groups. At the end of 1 year, significant between-group differences were found for selective attention, conflict resolution and muscular function only - no differences were found at any point for set shifting, working memory or gait speed. The Times reports the numbers correctly for the improved cognitive measures (improvement of 10.9% for the RTx2 group and 12.6% RTx1 group; decline of .5% for BAT group) but leaves out which functions showed no differences. Also not reported: peak muscle power increased by 13.4% in the RTx2 group but decreased by 8.4% in the RTx1 group and by 16.3% in the BAT group. I thought this was very interesting - does this indicate that weight training once a week was not enough to halt loss of muscle power? I supposed it helped slow the decline, but still...I'm not exactly sure how to interpret these results, but it seems that if you are a woman between the ages of 65-75 and you want to improve or maintain muscle strength, once a week resistance training is not enough. Also interesting: improvement in selective attention & conflict resolution was significantly associated with improvement in gait speed (but keep in mind that there were still no significant differences between the groups for gait speed).
One final (and striking) finding that took the authors by surprise: whole brain volume decreased a small but significant amount in the two RT groups! Yes, in the two groups that showed improvement in executive function. I can hear the jokes about weight-lifters already starting to fly...but keep in mind these results may not generalize to men, women outside the tested age group (65-75) or even to those in the age group outside of the Vancouver area. The authors could only speculate as to the implications of this paradoxical finding. And nope, you will not read about that in the NY Times.
Wednesday, January 27, 2010
Wednesday, January 20, 2010
Last week, I read this article in the Jan 14, 2010 NY Times: Obesity Rates Hit Plateau in U.S., Data Suggest (http://www.nytimes.com/2010/01/14/health/14obese.html) I found this hard to believe, but hey, it supposedly came straight from the CDC - hard to argue with.
We examined this further in my class tonight. I must give credit to Joyce Vergili, EdD, RD, CDE for doing the breakdown for us in class. Some of the highlights are below. I was a bit surprised at this: The NY Times usually does an OK job, but they really did misinterpret this study, which only serves to propagate confusion.
The NY Times states that, "Americans, at least as a group, may have reached their peak of obesity, according to data the Centers for Disease Control and Prevention released Wednesday." This sounds like big news! Yet, go to the CDC website, and there is nary a mention of this mysterious data. Turns out, the numbers were actually published in the Journal of the American Medical Association (JAMA) using data from the ongoing NHANES (National Health and Nutrition Examination Surveys). It was not "just released" data. It was NHANES data from 1999 - 2008. NHANES data is actually available to the public, if you care to learn how to manipulate the database.
Here is the link to the entire JAMA article, published online: http://jama.ama-assn.org/cgi/content/full/303/3/235
Anyway, where the NY Times really screws up is the following: "The numbers indicate that obesity rates have remained constant for at least five years among men and for closer to 10 years among women and children — long enough for experts to say the percentage of very overweight people has leveled off."
What the authors, Flegal et al., actually state regarding this is: "In 2007-2008, the prevalence of obesity was 32.2% among adult men and 35.5% among adult women. The increases in the prevalence of obesity previously observed do not appear to be continuing at the same rate over the past 10 years, particularly for women and possibly for men."
Let's be clear here. Did the authors say we have plateaued? No! They simply state the prevalence has changed. Has it slowed? Maybe. Seems likely. But stopped? No. Take a look back at the first sentence of the NY Times piece, when it states Americans "may have reached their peak of obesity." One classmate pointed out this sentence makes it sound as if rates are declining. I'm not exactly sure how Dr. Deitz (interviewed for the Times piece) can say we've "halted the progress of the obesity epidemic" based on these data. At the very best, it appear it might be slowing - very different than halting altogether.
The NY Times also fails to point out the weaknesses of the study, as noted by the authors (possible sampling error, reliance on BMI and that they limited statistical power: "The power of this study is limited to detect small changes in prevalence, particularly among subgroups defined by sex, age, and racial and ethnic group."
How many people reading the NY Times piece think we have now stopped obesity in its tracks?
Posted by Jacqueline J. Zimmerman at 11:46 PM