Once the sun goes down, the hallucinations, nightmares, confusion and paranoia begin for many people suffering from dementia.
This collection of symptoms is known as sundowning or sundowner's syndrome.
Each case of sundowner's varies from person to person, but symptoms can include becoming suspicious, demanding, upset and disoriented in the evening hours. Pacing or wandering the house while others are asleep is also common.
The condition is most common among those older than 85, according to Ann Laurence, director of education and training programs at Texas Tech's Garrison Institute on Aging.
Sundowner's syndrome is common in Alzheimer's patients, roughly 20 percent of whom experience confusion and anxiety at night, according to Laurence.
The exact cause of sundowner's is unknown, but most experts believe it to be caused by a combination of factors.
Some experts believe visual deterioration is one reason people suffering from dementia can become frightened in low-light situations. Brain function is also blamed for some of the confusion.
"As the neurons in the brain deteriorate, it affects your ability to perceive things they way they really are," Laurence said.
Fatigue is also likely to blame, at least in part, according to the Alzheimer's Foundation of America. A disturbance in the body's internal clock, or circadian rhythms, can basically switch a person's days and nights.
Sundowner's can make taking care of a loved one almost unbearable.
"It's the most common reason people are institutionalized because it wears the caregivers out," Laurence said. "They're not getting any rest."
Staying up with someone all night is exhausting, but medical experts warn against using sleep medications for people with sundowner's.
Studies have shown that non-drug therapies have better results than sleeping pills, Laurence said.
The most important thing a person can do to reduce the intensity of sundowner's is to get the individual on a proper schedule.
"It's very important to have a regular routine in the daytime," Laurence said.
Plan activities early in the day, and avoid naps in the afternoon, she said.
"Don't let the bed be a place where they can lounge around all day," Laurence said. "The bed is for sleeping."
Certain things should be avoided, like caffeine, which can keep people awake at night. Television should also be turned off in the evening hours to help calm the person down.
Light music, reading or looking at pictures can help calm a person down in the hours before bedtime, Laurence recommends.
Lending a hand
Sometimes, having someone they know nearby can settle a sundowner sufferer down.
"If they wake up at night and see a familiar face, it can help settle them down," said Tracy Baugh, owner of Lubbock's Home Instead Senior Care.
Jo Coffey, a caregiver with Home Instead Senior Care, said she sees a lot of sundowner's in her older clients.
"They change when the sun goes down," Coffey said. "They get very anxious at night."
One way Coffey calms her agitated clients is by listening to them - even if what they're saying isn't always based on reality.
"Their perception is their reality," Coffey said.
In one case, an 85-year-old woman in Coffey's care suddenly began searching her bed for her babies - who have long since grown and had children of their own.
Instead of telling the woman that her children were gone, Coffey returned the next day with a doll for the woman - a technique that she uses with many of her clients.
"They're comforted by being able to hold and cuddle a baby," Coffey said.