As the nation says goodbye to Ronald Reagan today, there is much to remember about the 40th president, but surely one of the most personal and poignant memories is his last great public act — his 1994 letter to America revealing that he had been diagnosed with Alzheimer’s disease. He would live another decade with the heartbreaking ravages of the disease, slipping ever farther away from loved ones, present in body but ever more absent in all the other ways that define our humanity.

Reagan was a powerful example of the fact that Alzheimer’s disease knows no boundaries of renown or affluence, of charm or grace or wit. This relentless disease of the brain took no more notice of this victim than of any of its millions of others.

There is no cure for Alzheimer’s, which afflicts about 5 million Americans. The incidence of the disease is increasing, primarily — and ironically — as a result of markedly longer lifespans made possible by medical advances. In the past, most people died of other causes before Alzheimer’s could afflict them. Now, about half of those 85 years of age or older suffer from the disease. About one in 10 of those 65 or older have Alzheimer’s.

New national tributes to Reagan have been discussed widely in the days since his death, but it is hard to imagine one more fitting, more consistent with his unabashed love for the American people, than expanded research into potential cures for the disease that steadily robbed him of memory and made his last years a void of incomprehension.

But there are obstacles to that, not just scientific obstacles, but political ones. Much of the most promising research into Alzheimer’s involves the use of embryonic stem cells. Such research is under way in private laboratories and in other countries, but here, in the nation Ronald Reagan loved and served, the use of federal funds for stem cell research is severely restricted.

That is a policy the Bush administration should reconsider, not merely in honor of Reagan’s memory, but also — and more importantly — for the sake of the millions of Americans who suffer from the disease, of the millions more who will suffer from it in the years ahead and of their families.

Shortly before her husband’s death, Nancy Reagan called for expanded use of stem cell research. “Ronnie’s long journey has finally taken him to a distant place where I can no longer reach him,” she said. “Because of this, I’m determined to do whatever I can to save other families from this pain. I just don’t see how we can turn our backs on this.”

How can we?