The number of Koreans aged 100 or more has almost doubled since 2005 under the country’s improved medical services, Statistics Korea said Tuesday.

The number of centenarians numbered 1,836 in November, posting a 9.1 percent increase from 961 in 2005, the state agency reported in its census report compiled every five years.

The number of females in the group, 1,580, exceeded their male counterparts, 256. But the number of male centenarians grew 146.2 percent over the past five years. The data comes as the country struggles to find long-term solutions to balance the economy with super-fast aging and low birth rate. The Organization for Economic Cooperation and Development on Tuesday advised the Korean government to raise its minimum pension-recipient age from the current 60 to 65 ― a measure which will increase tax revenue for welfare expenditure.

A subsidiary think tank of the Seoul Metropolitan Government in April said that senior welfare in 2030 would cost 1.4 trillion won (1.3 billion), about 2.3 times the current spending.

The statistics agency report said more than seven out of 10 are suffering from an illness, with 33.9 percent of the group suffering from dementia.

A total of 54.4 percent of healthy ones cited a well-regulated diet as the main reason for their longevity and 31 percent a low-stress lifestyle.

By Cynthia J. Kim (cynthiak@heraldcorp.com)