Wednesday, August 23, 2006

More NYT Nonsense

The New York Times health section is making it too easy today. Let's start with the final paragraph of this article to lay out the conclusion:

“They show quite convincingly, yet again, that overweight and, in particular, obesity, raise the risk of mortality,’’ Dr. Stampfer said. “It really should be the final word on this issue that’s arisen as to whether overweight is actually bad for you or not.”

Strong words, eh? Too bad he can't back them up. Here's the main claim being made regarding the modestly overweight:

The researchers said the more telling analysis arose when they focused on 186,000 healthy men and women who had never smoked. Among men and women, being overweight raised the risk of death 20 percent to 40 percent compared with normal-weight people, the researchers said.

Sounds scary. Let's examine some of the methodological issues so that we can aspire to the correct level of scared-ness. First, the population is drawn from those in the AARP. As the article acknowledges:

Because all the participants were recruited from AARP, they are not exactly representative of the population as a whole, and the participants reported their weight themselves, which contributes to some uncertainty in the results.

Kudos for the honesty.

Dr. Leitzmann said neither factor would probably skew the results considerably because “it’s a very large sample of people.”

Statistically the word skew has a specific meaning and the more correct term would be bias. Also, the good doctor is full of it. A large, non-representative sample is still non-representative. One possible advantage is that with a large enough sample you could select a random subsample that is representative of whatever population you're trying to capture (in this case the whole US). The article does not say whether they did this or not.

Secondly, the size of the sample reduces uncertainty but it does not reduce bias. In this case it means that peoples self-reported weight has been measured very accurately. It does not mean that their actual weight has been measured accurately at all.

Errors in reporting weights — people sometimes say they weigh less than they actually do — would also not produce a large effect, he added.

At least he acknowledges the potential bias, but, as I said above, it is not possible to know if the results are truely accurate or not.

Additionally, the mechanism for categorizing people as overweight is the body-mass index (BMI). The BMI was invented over 150 years ago. Its purpose is to categorize those with average body composition. Anyone with abnormal body composition, will not be categorized correctly. As an example, I am just below the overweight cut-off with my BMI, even though I am in excellent health. The disparity is due to my lifting weights and the subsequently higher muscular composition of my body.

“No single study is able to solve a controversy of this magnitude,” Dr. Leitzmann said, but he recommended that anyone overweight “should be looking to lose weight.”


I have to respect his honesty in his conclusion here. He may be reaching a bit, but he at least acknowledges that his study is not the end-all be-all of all research. Unlike Dr. Stampfer, who was not involved in the study, but throws out the concluding quote found above. This study suggests the possibility that being slighly overweight increases mortality, but it does not even come close to being the "final word" on the subject.

The study is an example of an observational study, in which a sample of existing data is analyzed for correlations. These types of studies are far inferior to randomly selecting the sample and assigning people to one category or the other. Obviously this is not possible to examine this problem; it is not realistic to randomly assign certain people to be overweight or normal weight. That means that there will be no single study, no matter how large, that will definitively answer the question.

13 comments:

travisprice4141275437 said...

hey, I just got a free $500.00 Gift Card. you can redeem yours at Abercrombie & Fitch All you have to do to get yours is Click Here to get a $500 free gift card for your backtoschool wardrobe

Anonymous said...

BUY CHEAP SUPER VIAGRA ONLINE AND SAVE 70 % OF MONEY...
BUY CHEAP CIALIS ONLINE & SAVE more then 70% of YOUR MONEY
BUY CHEAP VIAGRA ONLINE. NO PRESCRIPTION

CHASE CARDS RATES

lucy said...

The chances of contracting erectile dysfunction goes up substantially with age, increasing significantly above the age of sixty-five-which is rapidly approaching for the baby boomers. Although erectile dysfunction becomes more likely with advancing age, there is certainly no age cutoff for a sexually fulfilling life. Some men enjoy sexual activity even in their eighties and nineties. http://www.buy-viagra-with-us.com

Anonymous said...

www.bailoutprizepatrol.com

They throw money at Tim Geithner!

オテモヤン said...

オナニー
逆援助
SEX
フェラチオ
ソープ
逆援助
出張ホスト
手コキ
おっぱい
フェラチオ
中出し
セックス
デリヘル
包茎
逆援
性欲

mollyabraham said...

Generic Viagra contains Sildenafil and it is a prescription drug used to treat erectile dysfunction. Erectile dysfunction is the inability of the penis to become rigid, or stay firm long enough to complete the sexual act.

reggiewhite said...

Generic Cialis is the only drug which is not only fast acting (works in 30 minutes) but is also know to be effective for as long as 36 hours,

johnnysmith said...

Generic Cialis is slightly different from the other erectile drugs available in the market as it may work up to 36 hrs after dosing. Generic Levitra orks along with sexual stimulation to help achieve an erection when taken 30 to 60 minutes before sexual activity.

Anonymous said...

Generic Viagra is the medicine that is recommended by doctors worldwide for erectile dysfunction. It is the chemical composition of both forms of this drug and helps to cause erection on stimulation of the penis by inhibiting the enzyme phosphodiesterase type 5 which causes smooth muscle relaxation and a better erection.

how to write a bibliography said...

Nice article, i appreciate for putting this together! "This is obviously one great post. Thanks for the valuable information and insights you have so provided here. Keep it up!"
how to write annotated bibliography | dissertation | how to write an annotated bibliography

Anonymous said...

yeah~i think i agree with you~

yes~you said was right~


women Swarovski
women jewelry
jewelry
eyewear sunglasses
eyewear fashion sunglasses
Swarovski Earring
Swarovski Necklace
Swarovski Ring
Chanel sunglasses
Oakley sunglasses
Cartier sunglasses
Gucci sunglasses
Versace sunglasses
Prada sunglasses

wedding dresses said...

Article is very interesting,thanks for your sharing. I will necessarily add it in the selected works and I will visit this site.

Mens indowestern said...

Life is just like a war zone, if you want to get something, he must be very hard to get. The wisdom of the capitulation was equal to its humanity. Its moderation and justice stood in direct opposition and contrast with the domineering .