A year or so later, she witnessed her mother get frustrated and confused at the grocery store, snapping rudely at the cashier - something she wouldn't ordinarily do. The shock of seeing her erratic behavior was enough to lead Emily and her father to make a doctor's appointment for Linda.
In early 2014, at age 62, Linda was diagnosed with early-onset Alzheimer's disease.
Soon after, Emily began to notice an odd cyclical pattern to her mother's behaviour. As day turns to night, Linda becomes more disoriented, irritable and upset. "She's more likely to repeat herself, have mood swings and get frustrated," Emily said. "If she's in a new place during the late afternoon, she'll get really confused and want to go home."
A clinical phenomenon
Linda is one of millions worldwide who experience a clinical phenomenon called sundowning, typically seen in people suffering from dementia or cognitive impairment. Also known as sundown syndrome, sundowning refers to the emergence or worsening of neuropsychiatric symptoms such as agitation, aggression and disorientation in the late afternoon or early evening. Like some sort of spell has been cast, their behaviour can switch from normal to highly erratic come nightfall.
"It can be a pretty stark contrast from day to night. We have to deal with this a lot in nursing homes, and it's not uncommon for patients who have been having a good day to suddenly believe it's time to go home," said David Trinkle, associate professor of psychiatry and behavioral medicine at Virginia Tech, who has treated Alzheimer's patients for almost 30 years. "That's when you'll see patients try to leave the facility, and they will get extremely aggressive with screaming behaviour. I've had patients frequently call 911."
Studies on prevalence rates show large variability depending on the setting and population, but sundowning has been observed in 10 to 25 per cent of those with moderate to severe dementia in nursing homes and up to 66 per cent of people with Alzheimer's living at home. It also reportedly occurs in some cognitively intact elderly individuals and could be considered a sign of forthcoming dementia.
The cause of sundowning remains a mystery. Some physicians believe it has to do with lowered visibility that comes with darkness and shadows, or in some cases the shift change of hospital staff that happens around late afternoon. More recent research suggests it could be related to a disruption of the brain's internal master clock, which prompts the emergence of behaviour disturbances at sunset.
"There's not a whole lot known about what mechanisms might be involved in sundowning, and it's very poorly understood," said William "Trey" Todd, a research fellow in neurology at Harvard Medical School. "But the fact that the symptoms seem to follow a pattern, with worsening in the late afternoon or early evening, suggests that something is going on with the circadian system."
An explanation in early symptoms
Indeed, one of the earliest symptoms seen in Alzheimer's and other neurodegenerative diseases is a disruption in the normal circadian rhythms of the body. These biological changes follow a near 24-hour cycle, influencing key bodily functions such as the sleep-wake cycle, hormone release, digestion and body temperature. Keeping all these functions in sync is a master clock known as the suprachiasmatic nucleus (SCN), a collection of 20,000 nerve cells in the brain. This tiny, wing-shaped structure has the great responsibility of coordinating all the biological clocks in the body.
So how does the SCN manage to find the right time? The SCN takes in information about environmental light levels from the eye so it can synchronize itself - and the rest of the body - with the natural light/dark cycle. For instance, in response to darkness, the SCN tells the brain to release more melatonin, a hormone that prepares the body for sleep and aids drowsiness.
Recent studies have found that disturbances in the circadian system can occur years before the emergence of more classical symptoms such as memory loss and may even lead to the onset of disease. Individuals with Alzheimer's tend to have increasingly fragmented sleep. Melatonin release fails to happen at night as it should, and the natural rhythm of core body temperature is disturbed. Other studies have identified excessive daytime sleepiness and sleep behavior disorders as independent predictors of Alzheimer's, Parkinson's and cognitive impairments associated with dementia.
In a study published this year, Todd and his colleagues discovered that the circadian clock also regulates an emotion seen frequently in sundowning: aggression. In male mice, aggression followed a daily cycle driven by the SCN, as measured by how often they attacked intruder mice. After disrupting the neural pathway from the SCN to the part of the brain associated with aggression, the mice lost this natural rhythm. Instead, they would attack more frequently during times that control mice would start their resting phase.
"This may mean that the body's internal clock regulates emotional patterns, and if you disrupt the circadian pathway that would keep that within the right timing, you can have really profound changes in behavior at certain times of the day," Todd said. "We thought then that there might be some implications of our results for sundowning."
Some previous studies on humans do suggest that damage to the circadian system can influence the severity of sundown syndrome. For instance, a 2001 study on 25 inpatients with Alzheimer's disease found that patients who exhibited sundowning on a regular basis had profoundly disturbed circadian rhythms of activity and temperature - much more so than those who did not sundown. But whether individuals with dementia have damage to the SCN or its pathways that cause sundowning isn't yet known.
How can they be helped?
No cure exists for sundowning (or for Alzheimer's and other types of dementia, for that matter). But experts say there are ways that providers and caregivers can help sufferers feel more at ease when darkness sets in.
David Scales, an assistant professor at Weill Cornell Medicine who has written about his experience with sundowning patients, said the best medicine is prevention: keeping them awake and active during the day and then making sure they get a good night's sleep if possible. Creating a conducive sleep environment is important.
"Try to give them [sleep aids] that are more natural like melatonin, since sleep medications like Ambien that younger people might use can actually exacerbate delirium in elderly people," Scales said. "There have been times where I've literally given patients a Tums, a glass of milk and tucked them in real nice to help them get into that bedtime routine."
Sticking to a routine is key for many Alzheimer's patients.
When they aren't at the house, Emily and her father have a caregiver come in at the same time every day to take Linda, now 67, to the park with her dog and the nearby beach to watch the waves. Her best time is in the middle of the day, from about 11 a.m. to 2 p.m., so that is when she'll be active outside the house and also see visitors.
"It's more effective to act on the environment than to administer pills or psychoactive drugs that can further increase their confusion and other side effects," said Marco Canevelli, a neurologist at the Sapienza University of Rome. "For example, some studies support the effectiveness of bright light exposure during the day for the reduction of sundowning in patients."
For Emily, figuring out ways to alleviate her mom's sundown syndrome has been a long process of trial and error. Last fall, she came back to the house in the late afternoon after running some errands and found herself strangely locked out, despite her mother being home. It turned out that Linda had already been asleep in bed with all the doors locked, thinking it was nighttime.
Now Emily knows that the early darkness of autumn due to daylight saving time confuses her and has to be accounted for. She also sought advice for sundowning and other issues from organizations such as the Alzheimer's Foundation of America, which runs a daily toll-free hotline with licensed social workers available to answer any caregiver questions.
Despite going through earlier stages of frustration and mourning, Emily said she now feels incredibly grateful to still have a mother - one who still enjoys dancing and parties, nurtures her artistic spirit with drawing and coloring, and remains a joy and inspiration to everyone around her.
"After her diagnosis, I wasted a year of my life crying that I could never ask my mom for a piece of advice again, and that I'd never have my mom's Thanksgiving dinner again, and she'd never meet my kids - so many things that I didn't need to worry about," she said. "My real concern should be, what difference can I make in her life right now?"
