At first, Dr. Robert Zorowitz thought his 83-year-old mother was confused. She couldn’t remember passwords to accounts on her computer. She would call and say programs had stopped working. But over time, Zorowitz realized his mother—a highly intelligent woman who was comfortable with technology—was showing early signs of dementia. Increasingly, families will encounter similar concerns as older adults become reliant on computers, cellphones, and tablets: With cognitive impairment, these devices become difficult to use and, in some cases, problematic. Computer skills may deteriorate even “before [older adults] misplace keys, forget names, or display other more classic signs of early dementia,” Zorowitz wrote recently on a group email list for geriatricians. (He’s based in New York City and senior medical director for Optum Inc., a health services company.) “Deciding whether to block their access to their bank accounts, stocks, and other online resources may present the same ethical dilemmas as taking …