One minute, 82-year-old Robert Henline was headed to bed after a nighttime snack of a sandwich and ice cream.

The next time his daughter and son-in-law checked on him in their Monroeville home, he was gone into the frigid January night without a goodbye.

Like the majority of the more than 5 million Americans with Alzheimer's disease or other forms of dementia, Mr. Henline is a wanderer. It's a tendency that shows up unpredictably. Equally unfathomable is where the roaming will lead. The only hope is that the wanderers are found in a matter of hours rather than days.

"The person doesn't know they're lost -- that's the hard thing about this," said Erica Hood, vice president of programs and services for the Greater Pennsylvania Chapter of the Alzheimer's Association. "They may wander into a river and drown. They don't perceive the safety issue of wandering into water or thick brush. They may not cry out for help because they don't understand the situation they're in."

Increased focus on Alzheimer's has helped spread the use of devices that identify and track people with memory impairments, and spur a number of states to enact Amber Alert-style laws to enhance public searches for those who go missing.

Even with the new interest, the special bracelets are worn by only a small fraction of afflicted individuals, and fewer than one-fifth of states have laws to aid in finding older adults.

A rash of dementia-related cases has been reported by authorities in the region in recent weeks. Among them were a man who walked away from his Homewood residence; a couple who drove off from their Fayette County home without explanation; a woman reported missing from home in Brookline; and a Westmoreland County man who became lost in the middle of the night while driving.

All those individuals were found safely within 24 hours, two of them, with mild impairments, returning home on their own. Mr. Henline himself was discovered by Monroeville public works employees just five hours after police, firefighters, neighbors and other volunteers had begun an intensive search.

He had the poor judgment, however, to step outside on one of winter's coldest nights, with temperatures in the single digits. His daughter and son-in-law have a system of door locks and alarms to make it hard for him to leave the house undetected, and one of them is always home with him. But in this case he walked out before they set the devices.

Mr. Henline ended up on a neighbor's back porch about 500 yards away from his daughter's home, with his coat draped over him like a blanket, oblivious to the risk or community alarm.

"His remark to [the searchers] was, 'Where have you been? I've been sitting here waiting for you,' " daughter Lorrie recently recalled.

He required five days of treatment in January at Forbes Regional Hospital to regain his normal body temperature and health. He went home for several months, but required amputation of two toes -- and eventually his entire left foot -- from either frostbite or from sores he sustained in the early morning of Jan. 21. He is recovering at HealthSouth Harmarville Rehabilitation Center.

It could have been worse, and it has been for some Alzheimer's patients, who represent 13 percent of the population over age 65. The disease is the seventh-leading cause of death in the United States.

The vast majority of those with Alzheimers die in nursing homes, hospitals or at home. No statistics are kept on those found dead after wandering. Anecdotally, however, it's clear such fatalities are not uncommon.

The body of a 94-year-old man with Alzheimer's from Somerset, Washington County, was found in a ravine near his home Jan. 9 after his wife reported him missing.

Last November, a 91-year-old Cambria County resident was found dead on the ground near his car in a rural part of Blair County four days after he left home.

In October 2006, hunters found the body of a Herminie, Westmoreland County, man in a farmer's field. He had been reported missing by relatives, who said he lived alone and sometimes wandered.

And in 2005, a North Braddock man's body was found at the bottom of a steep hillside, a West Deer man died on a golf course after several days of exposure to cold temperatures, and an Ohioville, Beaver County, resident was found dead in a lake more than a week after disappearing.

The Alzheimer's Association estimates that at least six of 10 people with the disease will wander at some point, though the instances may be sporadic rather than regular. It's not known what triggers the movements, but Ms. Hood said it arises more often when people are bored and lacking sufficient activities and exercise.

Dr. David Wolk, a University of Pittsburgh professor who treats Alzheimer's patients as a neurologist at UPMC, said the tendency to wander arises more frequently in the later stages of the disease and is heightened when people are in unfamiliar environments, seeking out something they recognize -- usually to no avail because of their condition.

"They have trouble knowing the relationship of different places," Dr. Wolk said. "They may feel confident going off. And then trying to figure out where they are, they get further lost. ... Even mild patients living alone might have a sense they can do things they're used to, but when they end up in a situation outside their specific routine, they can end up lost and really thrown off."

The mental impairments of Alzheimer's patients aren't necessarily matched by physical ailments, which means that instead of staying in the neighborhood, as Mr. Henline did, people sometimes walk for miles without stopping.

Others with access to a car will drive hundreds of miles, capable of operating the controls but no longer aware enough to use signs, maps or a friendly gas station operator to figure out where they are.

Ms. Hood said the risk for such people escalates after 24 hours, often because they're on medications for other conditions, which a caregiver would make sure they took if they were at home.

Unlike some other states, Pennsylvania has not passed laws establishing procedures for law enforcement agencies to share information with the public and one another when older adults are reported missing.

Colorado passed the first such measure in 2004, after two deaths of people with dementia. It tied its system -- called Silver Alert -- into its existing Amber Alert mechanism, with emergency broadcasts like those used in every state to help locate missing children.

At least eight other states have a version of a senior alert, with Ohio becoming the most recent through legislation enacted in March. Sometimes, the systems are less widespread than Amber Alerts, primarily encouraging law enforcement agencies to share information and protecting media outlets from responsibility if the information they broadcast is false.

State Rep. James Casorio, D-North Huntingdon, has introduced such a measure in Pennsylvania, but it has yet to be acted upon. One purpose of the bill, he said, is to get the word out within a few hours of a disappearance.

"Generally when a person is found alive, it's usually within a half a mile to a mile-and-a-half. Local media and police could alert local residents of communities to be on the lookout, because maybe they know Mr. or Mrs. Jones," Mr. Casorio said.

Local police officials, who receive far more missing-persons reports for juveniles than for elderly citizens, already alert the media when they think it's helpful. They say it's a myth that they wait 24 hours to take any missing persons case seriously.

"It all depends on the circumstances," said Trooper James Custer, of the state police in Uniontown. He recently investigated the case of Francis and Anna Shimko, a husband and wife both with dementia, who were missing for a night and day May 3 and 4 after leaving North Union and driving into West Virginia. They ended up about 50 miles from home, in Hundred, but Trooper Custer said there was no indication what route they took or where they thought they were going.

The Shimkos' vehicle was eventually spotted by the father of a Pennsylvania state trooper who was familiar with the report. Authorities met them, and they returned home safely, but their son says they are no longer permitted to drive.

Three days after the Shimkos were found, the bodies of an Ohio couple with dementia were found hundreds of yards from their car in southwestern West Virginia, in woods near Dunlow.

Willard and Patty Frye had been missing for nearly two months. Something possessed them to turn off a main road onto a side road, and then down a dirt gas-well road that ended near nothing. They set out on foot and died, looking for no one knows what.

In Pittsburgh last month, 80-year-old Jerome Hawkins wandered from home for the third time since moving here from Indianapolis in August to be cared for by his sister, Pearlean Coleman.

He was diagnosed with Alzheimer's about five years ago, but causes no problems for her and her husband on the Hill District's Sweeney Way except when he eludes the eyes of a large extended family that helps watch over him. He left a family gathering on April 30 through the garage, undetected.

The family notified police and combed the Hill District and North Side, since he had taken long walks to cross bridges over the Allegheny River twice last year before they became more careful about locking doors and gates. But this time, he strolled in his slippers to the South Side, where a security guard who had heard a report about him saw Mr. Hawkins on East Carson Street after 2 a.m. and notified police. He was taken to a hospital, cold but without injuries.

"The South Side, I just can't imagine that," Mrs. Coleman said. "He thinks he's going to someplace in Indianapolis. He said in the hospital, 'I was almost home.' He sees things completely different. Apparently, he doesn't know how to turn around, and if he gets lost he just keeps going."

In hopes of speeding any future searches, she is ordering an Operation Take Me Home plastic wristband bearing a radio transmitter that can be used to help locate him. Mr. Henline's daughter already obtained one for him, since she intends to bring him home from the rehabilitation center. It's one step they hope can avoid calamity.

"You hear these stories about those folks drowning or freezing to death -- that really is scary," Mrs. Coleman said.