WMG / Old

"Old" isn't loosely based on its own source material; it's a Stealth Sequel.

While not specifically spelt out, one could make it fit with the canon of the original graphic novel if you try hard enough; the pharmaceutical company stated that this group was trial 73 of their experiments... it's not impossible to say the group featured in the original graphic novel was from an earlier experiment. Not only that, but its likely that the journal Trent and Maddox find from a "science fiction writer" happens to belong to Henry Lascaride, a character who fits the profession. MOST of the rules of the aging processes happen to match up, with a few differences that could be explained away by the company adding various substances unknowingly to both groups before they arrived on the beach so they could observe different results.

Old is set in the Supernatural universe.

Aside any scientific explanation, like in "The Happening", about the events of the beach, this movie is easy to set in the Supernatural Universe. A beach that shortens the lives of its visitors, could have many explanations that the Winchesters would speculate:

1) A ghost is possessing the beach, probably one of a vain person, who following the cheating of his spouse for a younger lover, killed himself by throwing himself into the sea. His spirit returns and starts sucking the age out of the visitors as revenge.

2) A deity is doing this (or a tulpa): imagine that that area was once a sacred path of a fertility god/goddess, who would give fertility to his followers expected human sacrifices... only not dead ones. It would have just sucked their youth and life essence until they died of old age.

3) The obvious course... a witch did it... this is the modus operandi of several Vain Sorceresses that need to retain their youth. And to joke a little, in other words: "It was Agatha All Along".

The beach is sentient.

As noted on the Headscratchers page, the menstrual cycle makes no sense: if it moves as quickly as aging, girls would have periods every ~2 minutes, but if it works normally Kara's baby couldn't have been conceived so quickly. In this scenario, the cycle works normally, but the beach "knows" when conception is possible and therefore moves things along.

• For that same reason, bodies are aging faster but hair, fingernails, and metabolism is not moving at the same pace. The Beach is selectively accelerating processes that are much more existentially horrifying rather than annoying.

The police officer was working undercover

That many missing people at the same resort? The cop is unsurprised when the notebook corroborates the missing people from the past.

The Pharmacuetical company is a branch of the Umbrella Corporation.

Let's be frank. There is literally no real way that a pharmaceutical company (even one as advanced as this one) would be able to make those kinds of meds without a shit-ton of money and help.

There would be a Standalone sequel titled "Young"

Featuring Scatterbrained Seniors in a luxurious retirement home, they discover the Fountain of Youth in a private spa room, find themselves locked inside until they regress into infants, and that their caretakers are actually Human Traffickers illegally selling the de-aged baby seniors to adoption centers, while ridding of any investigators through Death by De-aging.