More than 1 out of 3 people suffering from depression last year were aged 65 or over, data showed Friday.

According to the data by the Health Insurance Review and Assessment Service, 680,000 people received treatment for depression in 2015, and out of the number, 224,000, or 33 percent, were senior citizens.

The number of the country's senior citizens receiving treatment for the disease increased by an average of 6.8 percent on-year in the past five years, the data showed.

Noticeably, the number jumped 13 percent in 2015 from a year earlier, the data showed, underscoring that the country's population is aging at a fast pace.

Medical experts, however, said depression among the elderly population is often misdiagnosed as dementia.

"There is still some prejudice among people in our society about mental disease, such as depression," said Lee Dong-woo of Inje University, urging more patients to actively seek treatment.

The number of senior citizens aged 65 or over rose to an all-time high of 6.57 million, or 13.2 percent of the country's population of 49.7 million, last year. (Yonhap)