TOKYO >> A group of Japanese researchers is developing a device in which a smartphone notifies epilepsy patients ahead of seizures via a sensor built into an undershirt. It would detect warning signs through fluctuations of the heart rhythm.

The group — comprising researchers from Tokyo Medical and Dental University, Nagoya University and Kumamoto University — expects the device could prevent users from suffering serious injuries or being involved in accidents that result from a loss of consciousness.

It plans to conduct clinical tests on epilepsy patients as early as this year.

Epilepsy seizures are the result of excessive electrical discharges from a group of brain cells. About 1 million people in Japan are believed to have epilepsy, and roughly 70 percent of patients are able to prevent seizures with medication. But the remaining 30 percent have intractable epilepsy, in which their seizures are difficult to control with drugs.

Currently, treatment for intractable epilepsy involves surgically removing the area of the brain that causes seizures. Another treatment sends electrical impulses to a nerve in the neck. However, the treatments come with the risk of memory loss or a permanently hoarse voice.

Researchers focused on the increase in heart rate that occurs prior to seizures. They developed a sensor — smaller than a human hand and housed on an undershirt users wear — that detects abnormalities in heart rate wave patterns, which become evident several minutes prior to a seizure. The group also developed a smartphone app that receives information from the sensor and alerts users with warning signals.

The group tested the system on seven patients and detected seizures with 86 percent accuracy.

Kensuke Kawai, a Jichi Medical University professor who specializes in neurosurgery, said there are a few issues to address before the system can be put to use, such as recognizing differences in the signs of seizures and improving its accuracy.

As for the upsides, “this system imposes less burden to the patients’ body and has little side effects,” said Miho Miyajima, an assistant professor at Tokyo Medical and Dental University and a member of the study group. “It can mitigate the mental burden of patients who go through their everyday lives in fear of seizures.”