It's not often that you find a public health scenario based on a joke. The Will Rogers phenomenon is responsible for increasing the lifespan for patient groups - without treating a single patient.
Will Rogers was a humorist, cowboy, social commenter and, if you listen to some people, jerk. He's credited with saying things that are clever, but not nice. He said one of these things during the Great Depression, and its target was both the poor Oklahomans who fled their barren farms and the Californians that they joined. Rogers noted, "When the Okies left Oklahoma and moved to California, they raised the average intelligence in both states."
This statement has formed the basis for what's sometimes called the Will Rogers Phenomenon and sometimes the Will Rogers Paradox - although it's not truly a paradox. It happens when transferring something from one grouping to another somehow raises the average quality level for both groupings.
The most common example is moving an entry from an encyclopedia to a dictionary. Even the shortest encyclopedia entry tends to be longer than a dictionary definition. Taking one of the shortest encyclopedia entries out of the encyclopedia will raise the average length of encyclopedia entries by eliminating the short entries that drag down the average. Putting it into the dictionary, where it comparatively long, will raise the average dictionary definition.
It's more interesting to see what the Will Rogers Phenomenon does in medicine. It saves lives. Technically. It does this without treating a single patient. Let's say the criteria for a disease widens, or the ability to recognize the disease increases. Suddenly a group of people gets moved from the list of healthy humans to the list of sick humans. Because they had a disease, they were sicker than the average healthy person. Taking them out of the "healthy human" list increases the life expectancy (or overall health, or mental wellbeing) of the healthy list.
On the other hand, they are less sick than the sickest patients on the "unhealthy human" list. Their illness was so mild, or in such an early stage, that until the criteria were changed, they weren't even considered sick. When a bunch of less-sick-than-average people are put on the "unhealthy human" list, the life expectancy (etc) of that list goes up to.
No one gets treated. No one necessarily lives one second longer than they otherwise would. But by reclassification means both lists get a longer life expectancy.