Small changes in a gene that is involved in controlling the levels of the neurotransmitter dopamine could influence how mobile elderly adults can be. A study reported in the Journal of The American Geriatric Society suggested that low levels of dopamine may be contributing to the slow, unsteady gait seen in some elderly people. Dopamine levels are also known to be low in the brain of Parkinson’s disease patients.
"Most people think about dopamine's role in mobility in the context of Parkinson's disease, but not in normal aging," said the senior study author Caterina Rosano, M.D., M.P.H., a professor of epidemiology at the University of Pittsburgh Graduate School of Public Health. "We were curious to see if a genetic predisposition to produce more or less dopamine was related to mobility in individuals who had some level of frailty, yet did not have dementia, parkinsonism, or any other neurological condition."
Dopamine can be released by cells in several places in the brain, and several genetic elements are involved in dopamine signaling, but in this work, the researchers focused on a gene called COMT. The COMT gene makes an enzyme that breaks dopamine down, which keeps dopamine levels under control.
The study analyzed differences in the COMT gene in over 500 adults over age 65 that did not have any history or indication of Parkinson’s disease. The researchers noted how frail each participant was and their gait; frailty is commonly seen in aging individuals experiencing a decline in physical and physiological function and an increased risk of poor health outcomes. They hypothesized that frail people are more susceptible to changes in dopamine levels brought on by COMT.
"We found that in older, frail adults, those who have a high-dopamine genotype are more likely to maintain a faster gait and may be more resilient to mobility disablement as they age," said Rosano. The research showed that frail individuals with a COMT genotype linked to high dopamine levels were ten percent faster when they walked than people with a COMT genotype connected to low dopamine levels.
"This ten percent difference may seem small, but it could make a big difference for a person walking across a busy street while negotiating traffic," said Rosano. "This difference is even more striking when you consider just how many complex genes influence walking."
The scientists are continuing this research; they want to measure how much dopamine is needed to provide more resilience to seniors with a slowing gait, who are losing mobility. It may one day be possible to supplement these levels to stave off the functional decline.
"There are a lot of individuals living in the community who have dopamine levels toward the lower end of normal who don't have Parkinson's disease or psychiatric conditions," said Rosano. "If we give dopamine to these people, could we make them more resilient? That's what we don't know yet."
Rosano suggested that seniors should try to stay as active as possible in ways that they enjoy.
"I love to see grandparents walking around holding hands with their grandchildren because they have to look where they are going, where the child is going, keep an eye on the surroundings and pay attention to what the grandchild is saying, all at the same time," said Rosano. "They get an amazing multi-sensory rehab, and it's fantastic."