Sunday, May 18, 2008

Another deceitful breast cancer scare

I first reproduce a media report below -- to which I would simply have responded that we were probably looking at a social class effect on both variables -- and then I reproduce an excerpt from a much more searching look by Sandy Szwarc:

Get your daughters off the couch: New research shows exercise during the teen years - starting as young as age 12 - can help protect girls from breast cancer when they're grown. Middle-aged women have long been advised to get active to lower their risk of breast cancer after menopause.

What's new: That starting so young pays off, too. "This really points to the benefit of sustained physical activity from adolescence through the adult years, to get the maximum benefit," said Dr. Graham Colditz of Washington University School of Medicine in St. Louis, the study's lead author.

Researchers tracked nearly 65,000 nurses ages 24 to 42 who enrolled in a major health study. They answered detailed questionnaires about their physical activity dating back to age 12. Within six years of enrolling, 550 were diagnosed with breast cancer before menopause. A quarter of all breast cancer is diagnosed at these younger ages, when it's typically more aggressive. Women who were physically active as teens and young adults were 23 percent less likely to develop premenopausal breast cancer than women who grew up sedentary, researchers report Wednesday in the Journal of the National Cancer Institute. The biggest impact was regular exercise from ages 12 to 22.

"This is not the extreme athlete," Colditz cautioned. The women at lowest risk reported doing 3 hours and 15 minutes of running or other vigorous activity a week - or, for the less athletic, 13 hours a week of walking. Typically, the teens reported more strenuous exercise while during adulthood, walking was most common. Why would it help? A big point of exercise in middle age and beyond is to keep off the pounds. After menopause, fat tissue is a chief source of estrogen. In youth, however, the theory is that physical activity itself lowers estrogen levels. Studies of teen athletes show that very intense exercise can delay onset of menstrual cycles and cause irregular periods.

The moderate exercise reported in this study was nowhere near enough for those big changes. But it probably was enough to cause slight yet still helpful hormone changes, said Dr. Alpa Patel, a cancer prevention specialist at the American Cancer Society, who praised the new research. And while the study examined only premenopausal breast cancer, "it's certainly likely and possible" that the protection from youthful exercise will last long enough to affect more common postmenopausal breast cancer, too, Colditz added.

If you were a bookworm as a teen, it's not too late, Patel said. Other research on the middle-age benefits of exercise shows mom should join her daughters for that bike ride or game of tennis or at least a daily walk around the block. Many breast cancer risks a woman can't change: How early she starts menstruating, how late menopause hits, family history of the disease. Even though the exercise benefit is modest, physical activity and body weight are risk factors that women can control, Patel stressed. "I'd say you and your daughter are getting off the couch," she said. "Women who engage in physical activity not only during adolescence but during adulthood lower their risk."


Excerpt from Sandy Szwarc:

There was a press release about a new study... sent out to media before the study was published in the medical journal... more than 500 media outlets reported on the study on the same day and all saying the same thing... Stop me if you've heard this before.

This week, people around the world were told about a new study of 65,000 women said to have found another threat for girls and young women who fail to exercise regularly: a higher risk for breast cancer, "which kills 40,000 American women every year." From the press release, media reported that parents should get their daughters off the couch because women ages 12-35 who exercise regularly can cut their risk for breast cancer by 23%. This study was said to be one more reason to require girls to take PE to stay in shape, said a Mercury News editorial.

Science isn't marketed through public relations firms, nor does it try to manipulate or scare you. If the media's lockstep coverage, verbatim from a single press release, wasn't enough of a clue that this was marketing and "science by press release," then your next clue was the size of the study. No, the bigger the study doesn't necessarily mean the findings are more important. In fact, it rarely does. The bigger the number of people studied, the less likely it is to have been an actual clinical trial, the only kind of study that can test a hypothesis and credibly suggest a cause or effective intervention. That's because good clinical trials are expensive to conduct, while those done in a computer, using numbers and data rather than people and verified clinical evidence, aren't.

Since we know all studies are not created equal, let's look at this one. Was it a randomized clinical trial that followed tens of thousands of women from age 12 and found that vigorous daily exercise resulted in fewer cases of breast cancer? No. The study, published in the Journal of the National Cancer Institute, was authored by researchers at Brigham and Women's Hospital and Harvard Medical School in Boston, which houses the largest and longest-running Rorschach test of epidemiology: The Nurses Health Study. This is a huge quarry of questionnaires gathered since 1976 from more than 120,000 nurses and has been used by its researchers to pick out characteristics in unlimited combinations to find all sorts of correlations and conclude just about anything they set out to find. Well over 500 such computer studies have been published from this database and many of the correlations reported even contradict each other.....


None of the relative risks were tenable and beyond random chance or statistical error for this type of study. This study was unable to find any credible relationship between exercise and premenopausal breast cancer. All of the relative risks hugged null (RR=1)....

In a 2005 issue of the Nurses Health Study Annual Newsletter, Walter Willett, MD, MPH, the principal investigator of the Nurses Health Study II, which is the cohort used for this week’s study, had a very different report on what the Nurses Health Study data had shown: “Being physically active doesn’t seem to offer women much protection against premenopausal breast cancer — and being lean actually seems to increase risk,” he wrote. His message on the exact same data calmly defused worries that premenopausal breast cancer is a woman’s fault. We’ll give him the last word:
Despite most efforts [to identify a cause or risk factor], premenopausal breast cancer remains something of a mystery, and women understandably feel frustrated when they’ve ‘done everything right’ and still develop this disease. Clearly, the usual advice to exercise and eat well is not enough to prevent breast cancer.


Stem cell find linked to memory

AUSTRALIAN researchers have discovered stem cells in the brain that are vital for learning and memory. They have also worked out how to activate the cells so they produce new neurons, a discovery that could eventually lead to better treatments for degenerative brain conditions of ageing, such as dementia.

The director of the Queensland Brain Institute, Perry Bartlett, said neuroscientists knew there had to be stem cells somewhere in the hippocampus - the part of the brain involved in important functions such as learning and memory - because people and other animals produced large numbers of new neurons in this region throughout life.

But the stem cells had proved extremely difficult to find. Professor Bartlett now understands why. His team has discovered that mice have only eight to 10 of these cells in this region of the brain. "And in humans there is probably not a lot more. You don't need a large number," he said.

As people get older they make fewer new brain cells, which reduces their mental functioning, particularly in navigation and short-term memory. "But we think that even though there is a loss in the ability to make new nerve cells, the machinery is still there. The exciting part is that we're starting to discover ways to activate the stem cells, even in aged animals," Professor Bartlett said.

Working with live mice and their brain tissue in the lab, his team produced a threefold increase in the number of cells in the hippocampus producing new neurons. "It's a pretty massive effect," said Professor Bartlett, of the University of Queensland, whose team's findings are published in The Journal of Neuroscience.


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