Your articles referred mostly to people with illness or sleeping desorder.it's well known that sleeping circle is part of the human growing process ,which is not the case anymore as you age.this is why we don't need 8-9 hours of sleep anylonger.
It has been proven that the physical need for sleep does not decrease once we reach adulthood. While there is a decrease in the amount of sleep among seniors, it is due to physical factors, not a decreasing need for sleep. You have taken a true statement (that seniors sleep less than their younger counterparts) and inaccurately jumped to the conclusion that seniors need less sleep while ignoring the medical factors that degrade seniors' sleep patterns.
Again, you are correct that we require additional sleep prior to adulthood (and pregnant women), but once we reach adulthood, the need for sleep remains static for the rest of our lives. It is the ability to get the proper quantity of sleep that becomes impaired as we age.
To paraphrase Wolfgang Pauli, you're not even wrong. http://en.wikipedia.org/wiki/Not_even_wrong