Older adults who are starting to have problems with memory may benefit from small amounts of nicotine therapy, according to a US study published on Monday.

The research in Neurology, the medical journal of the American Academy of Neurology, included 74 non-smokers with an average age of 76. Half were given a daily nicotine patch for six months, the other half wore a placebo patch.

Those on nicotine therapy showed better results on cognitive tests for attention, memory, as well as how fast and consistently they could process information.

After six months on the patch, the nicotine group "regained 46 percent of normal performance for age on long-term memory, whereas the placebo group worsened by 26 percent over the same time period," said the study.

However, the study authors cautioned that older adults should not begin to smoke cigarettes to help their brain function, and said more research is needed to see if the positive effects endure over a long period of time.

Also, nicotine is not likely to help people whose memory already works well, said study author Paul Newhouse, director of the Center for Cognitive Medicine at Vanderbilt University Medical Center.

"If you're already functioning fine, but slip down the hill, nicotine will push you back up toward the top. A little bit of the drug makes poor performers better," he said.

"Too much, and it makes them worse again, so there's a range. The key issue is to find the sweet spot where it helps."

The study was funded by the National Institute on Aging, and received no money from pharmaceutical companies, Newhouse said. Nicotrol 15 mg patches were donated for the study by Pfizer.

The link between nicotine and memory was first shown in the 1980s. Nicotine stimulates receptors in the brain that are important for thinking and memory.

People with Alzheimer's disease tend to lose some of those receptors.

Jeremy Koppel, a geriatric psychiatrist at Zucker Hillside Hospital in Glen Oaks, New York, who was not involved in the study, said more research is needed to gauge the true nature of nicotine's potential benefit.

"While this small study did find that patients treated with transdermal nicotine performed better on tests of attention, and some tests of memory, there was no evidence of global improvement in the group treated with nicotine," Koppel said.

"Further, this study does not provide evidence that nicotine can reverse or slow the progression from MCI (mild cognitive impairment) to Alzheimer's disease."

Newhouse said he hopes to next examine how nicotine therapy might change the curve of cognitive decline over time.

"I don't think it's going to become a treatment for Alzheimer's disease by itself. That would be like trying to rebuild a house after a fire when the fire's still going," he said.

"You need to prevent the fire. The holy grail would be changing the deterioration curve."

People who wore the patch reported some nausea, dizziness, and mild weight loss, but did not report any withdrawal symptoms once they stopped wearing it. (AFP)