The strong correlation between the two suggests there might be a link between the sort of thinking that people regularly do when not involved in purposeful mental activity and the degenerative disease that is characterized by forgetfulness and dementia, scientists who conducted the federally funded study said.

Avenue Between Brain Activity Patterns

Randy Buckner, a neuroscientist at Washington University in St. Louis, said the implications of the finding are far from clear. It is too early to suggest that daydreaming is dangerous, he said, or that avoiding such musings could make a difference to the risk of Alzheimer's disease.

Rather, he and others said, the study adds to the evidence that everyday mental and physical activities play an important role in the course of neurological disease.

"It suggests an avenue between brain activity patterns and Alzheimer's disease that we just hadn't been thinking about," Buckner, who led the study, said. "It is going to take some time to understand the relative potential of this link."

Unknown Third Factor?

Other neuroscientists agreed the work was intriguing -- and joked about its implications.

"There goes half my day," said Ronald Petersen, director of the Mayo Clinic's Alzheimer's Disease Research Center, about his own propensity for creative musing.

"It is really going out on a limb," he added of the new study. "But for the sake of generating discussion, it is interesting. It is useful to get people thinking along these lines."

Further research is under way to probe the link, said Buckner, who is affiliated with the Howard Hughes Medical Institute in Chevy Chase, Md.

While some unknown third factor may be responsible for triggering daydreaming as well as Alzheimer's, the neuroscientist said a causative link between the two would explain a mystery that has long bothered scientists: why Alzheimer's generally affects memory first.

Might Aid Creativity

"When we muse to ourselves and plan our day and think about the recent past, we tend to use memory systems," Buckner said. "Through some as yet unknown pathway or metabolism cascade, use of these systems may be what underlies Alzheimer's disease."

Although daydreaming is usually seen as intellectual downtime, Buckner said that might not be true. Such musings are far from passive, he added, and might help people be creative.