The spouses arriving for the Wednesday afternoon caregivers’ class at the Penn Memory Center in Philadelphia had something on their minds even before Alison Lynn, the social worker leading the session, could start the conversation.

A few days before, retired Supreme Court Justice Sandra Day O’Connor had released a letter announcing that she’d been diagnosed with dementia, probably Alzheimer’s disease.

“As this condition has progressed, I am no longer able to participate in public life,” she wrote. “I want to be open about these changes, and while I am still able, share some personal thoughts.”

It meant something to Ms. Lynn’s participants that the first woman to serve on the Supreme Court would acknowledge, at 88, that she had the same relentless disease that was claiming their husbands and wives (and that killed Justice O’Connor’s husband, too, in 2009).