This is not a study, it's just a test, therefore, their conclusion is invalid IMO. A study would follow a group of test subjects over the (hypothetical) 15 year interval, and so might draw some useful conclusions. The huge unanswered question here is, are the athletes they tested still active because their bodies naturally produce high(er) amounts of GH, or do their bodies produce high(er) amounts of GH because they're still active? The conclusion assumes the latter but I don't see where their test shows that to be a valid assumption. This is clearly an important question, esp. to older athletes considering supplementation.