OT: Exercise May Improve Odds Against Prostate Cancer Death

[Guest guest]

Quiz: Encouraging information but can anyone spot the main problem with the

study method, copied below?

>

Hi Vivian,

I agree with your analysis 100%! - you get the PAL consumer savvy award for

Jan 2011. : )

You wrote:

" Abstract suggests this is not a controlled scientific trial.

Obvious confound between survival and ability to engage in vigorous exercise

ie those who were in best health were those most likely to be able to engage

in vigorous exercise regardless.

All this study suggests is that people who are well enough to exercise

vigorously are also more likely to survive, which should be true even in the

absence of cancer.

Doesn't tell us anything about the impact of exercise on surviving prostate

cancer unless they do a controlled trial in which they randomly assign

varying levels of exercise to folks with prostate cancer and see what

happens.

Of course you'd also have to equally distribute other crucial factors like

age, other health status, how advanced the cancer is and what cancer

treatment is provided to know the additional impact of exercise.

Vivian

> Karl

>

> ==

> To explore how exercise might further improve the odds of survival,

Kenfield

> and her colleagues tracked the physical exercise routines of just over

2,700

> men who had been diagnosed with prostate cancer after 1990. The

assessments

> took place every two years.

>

> Activities that were assessed included walking, jogging, running,

bicycling,

> swimming, rowing, stair-climbing, and playing tennis, squash, racquetball

> and/or golf. Weight-lifting and arduous outdoor work were also included in

> the analysis, and all activities were given a so-called " metabolic

> equivalent task " ranking, or MET value, according to the amount of energy

> each required relative to being sedentary.

>

> After giving non-vigorous activities a MET ranking of less than 6 and

> vigorous activities a value of 6 and up, the authors determined how many

MET

> hours per week were expended by each patient based on the nature and pace

of

> each activity they engaged in.

>

> Ultimately, 548 of the patients died during the study period, one-fifth as

a

> direct result of their prostate cancer diagnosis. But the research team

> found that the more active patients had been, the lower their risk of

dying

> from prostate cancer itself or any other cause.

>

> The more hours the patients devoted to either vigorous or non-vigorous

> exercise routines, the better they fared in terms of survival. For

example,

> men who tallied as much as nine or more MET hours per week -- equivalent

to

> jogging, biking, swimming or playing tennis for 90 minutes per week -- had

a

> 33 percent lower risk for dying from any cause and a 35 percent lower risk

> for dying from prostate cancer than men who expended less than nine MET

> hours per week.

>

> Vigorous activity, however, seemed to confer a stronger survival benefit

> than non-vigorous activity. Compared with men who participated in vigorous

> exercise (such as biking, tennis, jogging, running, and/or swimming) for

> less than one hour per week, those who engaged in three hours or more had

a

> nearly 50 percent drop in death risk due to any cause and a 61 percent

drop

> in the risk of dying specifically from prostate cancer. In fact, only

> vigorous activity was linked to a drop in prostate cancer death risk, the

> study authors noted.