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Comment by clusterhacks | Hacker News Reader

From the abstract:

  Epidemiologic data from a 20-year prospective study of a large human cohort of 
  initially cancer-free participants revealed that exercise prior to cancer 
  initiation had a modest impact on cancer incidence in low metastatic stages 
  but significantly reduced the likelihood of highly metastatic cancer.

Data was gathered from a large cohort via questionnaire. Looks like the study then used responses to classify high vs low intensity.

From the article:

  The total study population included 2,734 participants; 243 new cancer cases 
  were recorded during the 20-year follow-up period.

It reads as if the study then had to reject data from 95 of the 243 patients due to not having a SEER score.

From skimming the article, I can't find any analysis of metastatic disease incidence in the remaining patients? Am I just missing it?

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The chief result being reported here is in the mouse model, it's not 100-some people filling out a questionnaire that got them on the cover of the journal.

Is that true? The headline here comes straight from the human study. From the article:

> The human data, obtained from an epidemiological study that monitored 3,000 individuals for about 20 years, indicated 72% less metastatic cancer in participants who reported regular aerobic activity at high intensity, compared to those who did not engage in physical exercise.

That figure comes from examining 148 people in that cohort who got cancer. The authors don't state what proportion of that number is metastatic cancer. They also state:

"As our focus was on the relationship between exercise and cancer, we used a propensity score of multinomial logistic regression to control for key variables in the diet assessed using a validated questionnaire."

So the 73% figure is drawn from a small number of cases that were significantly weighted. I'd be interested to hear what people who know this field think about this result separate from the mouse/human exercise stuff.

Totally agree. I am extremely annoyed at the general article submitted versus the actual paper focus.

While I respect the need for these longterm survey data collection efforts, I am not sure I would frankly trust that survey to even accurately be able to tease out high-intensity vs low-intensity efforts from people participating in the study.

And the tie-in from the cohort survey results back into the motivation for the mouse study just isn't done at all. I mean out of their 148 patients with SEER scores, they make no mention at all at metastatic disease occurence or even attempt to tie that figure back to exercise intensity . . .

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