Joe Lieberman proposes increasing the age of eligibility for Medicare from 65 to 67. This is rationing, pure and simple; costs will be saved simply by reducing access to care. However, as a method of rationing, there is a certain appeal to this proposal, because the youngest Medicare recipients are presumably the ones who need it least.
Nevertheless, this is a bad idea, for the following reason. Limiting access to Medicare will make it harder to prevent chronic illness, and if we can't prevent chronic illness, it will be hard to control health care costs.
Medicare costs are driven by a small group of very ill patients. Three-quarters of Medicare dollars are spent on patients with five or more chronic illnesses. Having multiple illnesses, unsurprisingly, makes it harder to treat any single illness, which is one reason why these patients are so expensive. Chronic illnesses are usually acquired gradually across a considerable period of time. Moreover, the patients with five illnesses at some earlier point had only four, those with four previously had only three, and so on. So in the long run, the core of health cost control ought to be the prevention of chronic illness, and early treatment of chronic illnesses so that they do not become severe.
This means that people who have diabetes, pulmonary disorders, depression, arthritis -- the list goes on and on -- should be diagnosed, given evidence-based treatments, and taught how to manage their illness when they acquire them, not when they turn 67. Or 65, for that matter, but the longer you wait, the worse things get.
Raising the age of Medicare will make it harder for 65 and 66 year olds to access care, and they have to access care to get these services. Keep in mind that if Lieberman's plan doesn't reduce access to care, it doesn't reduce health care costs. All that it does is shift health care costs from Medicare to some other payer.
See also criticisms of Lieberman's plan from Austin Frakt, Igor Volsky, and Ezra Klein. For more of my thoughts on prevention and health care cost, see here, here, here, and remember: In the long run, we are (almost all) chronically ill.