Intense, longer-term therapy can help stroke victims regain some arm movement years after their brain injury, U.S. researchers have found.

Rehabilitation normally starts immediately after a stroke and lasts six months. Conventional thinking has been that any rehabilitation beyond that initial period has little benefit for stroke survivors, but recent studies are starting to suggest otherwise.

A three-year randomized control trial of 127 veterans in the U.S. found that stroke victims who had 12 weeks of robot-assisted therapy for their stroke-damaged arm had an improved quality of life compared with those who had no additional therapy beyond the initial rehabilitation period.

The results of the study appear in Friday's online issue of the New England Journal of Medicine.

The veterans in the study had experienced a stroke that resulted in moderate to severe disability in an arm. The strokes had occurred at least six months earlier and, on average, five years earlier.

After six months, the 49 patients who received robotic therapy designed at the Massachusetts Institute of Technology showed clinically significant upper-arm function compared with the 28 patients who did not receive specific therapy for their upper limb.

Another 50 patients did similar high-intensity exercises with a therapist rather than with the aid of the robotic device and received a similar benefit.

To measure the impact on everyday life, researchers asked patients a battery of questions, such as how well they could cut food with a fork and knife, open jars, or tie their shoelaces. Patients were also asked about activities not directly related to their arms, such as walking or climbing stairs.

"We believe that by gaining more function and better control of their affected arms, patients were able to get out and do more, translating their motor benefits into additional meaningful social activity and participation," the study's lead author, Dr. Albert Lo, assistant professor of neurology at Brown University in Providence, R.I., said in a news release.

The patients in the robot-assisted therapy group sat at a table with their stroke-affected arm attached to the device and were asked to move a cursor on a screen. The robot sensed if they had trouble performing the task and assisted their movements. George Wittenberg, a neurologist at the Providence VA Medical Center and the study's lead investigator in Baltimore, likened it to "power steering" for the patients' arms.

Stroke rehabilitation, with or without robots, seemed to help the stroke-damaged brain learn to compensate for the lost function and begin to rewire itself, the researchers said.

The researchers think that boosting arm function helped patients to be more active overall, which led to greater improvement in their health.

The study is important, especially in showing that robotic therapy is better than "standard" therapy, though no better than intensive therapy, said Dr. Howard Kirshner, a professor and vice-chair in neurology at Vanderbilt Medical Center North in Nashville, commenting on the study.

The findings also suggest it may be more practical to introduce robotic therapy, which is is mainly available at centres that do intensive therapy, he added.

"The most important take-away message for stroke survivors is that therapy, whether using new-fangled technologies, or using intensive standard therapy by trained therapists, is essential for optimal recovery of function after a stroke," Kirshner said in an email.