OSAKA (Kyodo) The Research Institute of Human Engineering for Quality Life and Matsushita Electric Works Ltd. have jointly developed a computerized device that measures how deeply a person is sleeping by taking a pulse, the Osaka-based research institute said Monday.

The device classifies the state of a person’s sleep according to four grades — almost awake, sleep with rapid eye movement, shallow sleep and deep sleep — by measuring pulse-rate fluctuations.

The quality of sleep is then divided into nine grades, taking into account data such as the ratio of deep sleep to total sleep, the time it takes to fall asleep, and the pulse rate.

The institute and Matsushita are seeking to improve the accuracy of the device and to commercialize the product, which could free analysts and doctors from having to use a costly electroencephalogram for measuring brain waves, an institute official said.

Subjects wear a ring-shaped sensor and a bracelet transmitter that relays data to a computer.

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