(MONEY Magazine) – From outside his Victorian house in Boston, Barbara Hoyt's uncle was looking great. At 91 he could mow his own lawn and run the snowblower down his sidewalk in the winter. But inside, as Barbara discovered when she visited her uncle after his wife broke her hip, things were disturbingly different. Nine months' worth of unpaid bills were on her uncle's desk -- including a chilling notice warning the couple that their health insurance was about to be canceled. It was this peek behind their comforting facade that convinced Barbara that her aunt and uncle needed her help. Unopened bills, bounced checks and bouts of forgetfulness (did they miss your last birthday?) are among the first tip-offs that an elderly person is faltering, says Dr. Jill Rhymes, director of geriatric educational programs at the University of Chicago. A serious illness such as a stroke, ''silent'' heart attack or Alzheimer's disease can derail an older person's reason, memory or other cognitive functions. But so can something as transient and treatable as a reaction to a medication, a thyroid problem, depression, anemia, vitamin deficiency, pneumonia or even a common cold. ''Often one spouse will cover up for the other, and problems can go undetected by outsiders for years,'' says Rhymes. Sometimes changes in mental ability, energy level or mobility occur so gradually that the other spouse adapts without really acknowledging the problems. But more often the healthy spouse is too embarrassed to raise the subject with the kids. ''The children may finally realize that it's always Dad who answers the telephone now,'' says Rhymes, ''or that at family dinners Mom looks at Dad for help with a simple question.'' If you suspect your parents are losing control of their lives, you might start keeping a closer eye on some of their personal affairs. Signs of trouble include finding moldy food in the refrigerator, unfilled prescriptions tucked away in a drawer, or an overdrawn bank account. If you notice that your parent is less able to perform simple activities like walking, dressing and eating, don't assume these symptoms are a normal part of aging that can be overlooked. Notes Christine Marek, a geriatric nurse practitioner and president of Geriatric Nursing Service in Glastonbury, Conn.: ''One of my patients, in his nineties, has every disease in the book. He's had three heart attacks and suffers from respiratory problems, diminished eyesight and diabetes. But he lives alone, cares for himself, reads the paper every day and has strong opinions about current events.'' If an impairment you've noticed persists, encourage your parent to undergo a thorough medical evaluation. Today, every large U.S. city offers consulting services where your parent can be examined by a geriatrician, geriatric nurse and social worker. The evaluation usually takes several hours, and medical recommendations will be sent back to your parent's regular doctor. Elderly people who are aware of their faltering abilities may resist the idea of an evaluation for fear that the results will be used to force them into a nursing home. If that is not the case, say so to put them at ease. It is important to enlist your parents' help in trying to solve the problem, so they know you're not trying to usurp their independence and take control of their lives. ''Whenever possible, stick to the position that your parents know what's best for them,'' says New York City psychologist James Halpern. ''If you're too helpful, you'll encourage your parents to become helpless.''