One of the study's participants said in an interview that he felt like having played for so long was akin to "an insurance policy," Hanna-Plady said.
The researcher's more recent study showed that musicians who began playing before age 9 had better verbal working memory functions than those who started later or didn't play at all.
This finding is consistent with verbal language acquisition -- linguistics studies have shown that there is a critical period during which the brain is open to learning a language, and fluency becomes far more difficult after a certain age in childhood.
It also jives with the findings of a 1995 study that showed professional musicians who began training before age 7 had a thicker anterior corpus callosum, part of the pathway that links the right and left hemispheres of the brain.
And participants who continued to play their instruments at older ages tended to perform better on tasks of visuospatial judgment, "suggesting that there continues to be plasticity in advanced age," Hanna-Pladdy said.
"Finding a way to harness this plasticity is probably one of the biggest hopes we have for treating brain disorders or dealing with cognitive decline in advanced age," she said. "Similarly, continuing to play music in advanced age added a protective benefit to individuals with less education, which has previously been demonstrated (to be) one of the most robust ways to create cognitive reserve. Thus, musical training appears to be a viable model for cognitive stimulation, and can be conceptualized as an alternate form of education."
Should we start now?
Is it worth it then to teach an older person to play an instrument, perhaps one who already shows signs of cognitive decline? Recent research suggests it's harder, but still possible, to modify the brain in an older person. But no one has a definitive answer on whether teaching an elderly person a new instrument would lead to the same kinds of benefits that scientists have found in lifelong musicians.
"It would be pretty challenging, considering they're having a hard time remembering," Hanna-Pladdy said of dementia patients. "It may be beneficial to provide musical stimulation to individuals in the earlier phases (referred to as mild cognitive impairment) or to re-initiate musical practice in individuals who are no longer engaged."
Regardless, since people find music enjoyable, trying to learn an instrument won't hurt. But more research is needed over a long period of time to assess fully the benefits of music among elderly people, Hanna-Pladdy said.
Evidence may continue to emerge that long-term music playing has a preventive effect against dementia, but that's not to say that nonmusicians are totally out of luck, Hanna-Pladdy said.
Music is becoming a hot area of study because it's easier to quantify the number of years that people play music than, for instance, the length of time reading or playing games.
"This is just meant to be a model for cognitive stimulation, and how cognitively stimulating activities can change your brain," Hanna-Pladdy said.
So music may be good for you, but so may other pastimes.
After all, violinist Frank Iacono and his wife, Mary -- married for 66 years -- play Scrabble together every night.
For patients who already have dementia, music can be used in a different way to help the mind.
The emotional response that people get from listening to music, and the brain chemicals associated with pleasure that get released in the process, are distinct from the structural changes in the brain that playing music over time may instigate, scientists said.
Trends emerging from research show that music exposure -- whether through casual listening or more formalized music therapy -- can help reduce the incidences of behavioral issues and generally calm dementia patients, said Beth Kallmyer, vice president for constituent services at the Alzheimer's Association.
"Anecdotally what we hear is that people can be upset, even a little agitated, and when they're listening to music, even in the late stages, people can appreciate music," Kallmyer said.
Family members should help caregivers choose music that is meaningful to a person with dementia, she said. "The most important thing is keeping your interventions person-centered as much as possible."
Naomi Ziv of the Academic College of Tel Aviv Yaffo in Israel and her colleagues showed in a Journal of Music Therapy study that background music is associated with an increase in positive behaviors -- laughing, smiling, talking -- a decrease in negative ones, including aggressiveness and crying.
Music attracts attention; it also enhances focus and affects emotion, Ziv told CNN in an e-mail.
"When we hear familiar and preferred music, we mentally follow it," she said. "It seems that whereas general memory deteriorates in dementia, memory for music remains relatively intact."
Familiar or preferred music evokes memories and influences mood, which is perhaps the underlying reason for these results, Ziv said.