Looking at 17 past studies, British researchers found evidence that watering plants, or sitting or strolling in a garden can help soothe some dementia patients' anxiety.
The study authors cautioned that the effects of gardens on dementia patients are a tough subject to study -- and the evidence of a benefit is limited. But experts said it's encouraging that there is ongoing research into the potential calming power of outdoor space.
As dementia progresses, it's common for people to become anxious, restless and agitated, according to the Alzheimer's Association.
Sometimes there is a medical reason -- such as chronic pain -- that the person with dementia just can't explain, said Dr. Mark Stecker, chairman of neurosciences at Winthrop-University Hospital in Mineola, N.Y.
Often, though, the problem stems from the dementia itself. Then, families and caregivers can try offering reassurance and being a calm presence, explained Stecker, who was not involved in the new study.
"Just a nice smile can help," Stecker said. "Even when we can't understand language, we know, from the time we're children, what a smile means."
It can also be helpful to offer dementia patients a "distraction," such as playing a game or taking a car ride, Stecker said. "And that's where something like a garden could fit in," he added. "It can provide a distraction."
While that makes sense, it's a difficult principle to prove in a study, Stecker noted.
In the new review, published online recently in the Journal of the American Medical Directors Association, researchers found evidence that gardens at nursing homes helped lessen some residents' agitation. But the effects of gardens are much harder to pin down than the effects of a pill, for instance. And, Stecker noted, agitation in dementia patients is challenging to measure.
So the studies that have been done so far have tended to be of "poor quality," said review author Rebecca Whear, a research fellow at the University of Exeter Medical School.
It's too soon to recommend that nursing homes and day programs for dementia patients start routinely growing gardens, according to Whear.
"This work shows that their use could be beneficial," she said, "but much more research is needed."
That's in part because there are safety issues that come up with dementia patients.
"The idea of having an outdoor space is great, but it also has to be a safe space," said Dr. Gisele Wolf-Klein, director of geriatric education at the North Shore-LIJ Health System, in New Hyde Park, N.Y.
"First, 'wander-proofing' the space is absolutely essential," said Wolf-Klein, who was not involved in the study. "You also have to be very mindful about the surface, to lessen the risk of stumbling or slipping."
And because some dementia patients are prone to putting things in their mouths, the plants in the garden have to be non-poisonous, Wolf-Klein said.
And no matter where the garden or other outdoor space is -- at a nursing home or the family home -- people with dementia need to supervised, both Wolf-Klein and Stecker stressed.
With safety measures in place, they said, gardens -- or some type of outdoor space -- could be soothing to some dementia patients. "It's not unusual to have a geriatric patient who used to garden," Wolf-Klein said. "So, being in a garden could bring them back to a comfortable time in their life."
Stecker agreed. "When the brain is impaired, we go back to our basic instincts. Many people have always enjoyed the outdoors. They may not have an explicit memory of that, but it's an implicit memory. And they find it comforting to be outside."
Stecker said he hopes more care homes consider the idea of constructing a safe outdoor space. For family caregivers, he said, it may not take a garden. Simply going out to the patio, taking a short walk, or going to the local park could work just as well, he said.
For some dementia patients, though, the outdoors may not prove helpful at all, since being outside can be more disorienting than comforting. "It's not a panacea," Wolf-Klein noted.
Stecker agreed. "It's all going to depend on the individual," he said.
The Alzheimer's Association has more on dementia and agitation symptoms.