Japanese officials have confirmed that more than 230,000 people listed as alive and at least 100 years old in Japan cannot be found, including 884 who would be 150 or older.
Japan, famed for its longevity, launched a nationwide survey after a recent string of grisly discoveries -- including a mummified man in his bed and an old woman's remains in a backpack -- sparked alarm over the fate of many elderly.
The cases also triggered soul-searching over elderly people living in isolation, and public outrage at relatives of those missing who have kept their deaths secret in order to keep receiving their pension payments.
Many of those whose whereabouts were unknown may have died as long ago as World War II or in the post-war turmoil, or may have emigrated without their status being reported to local authorities, the ministry said.
The list included 77,118 people who would be 120 years or older today, and 884 who would be at least 150 years old, the ministry said.
The government has instructed regional legal offices to delete the names of people aged 120 or older if their whereabouts cannot be confirmed.
The ministry said the impact on Japan's life expectancy figures would likely be minimal since these are calculated from separate data gathered in home visits by field workers during national census campaigns.
Japan's health ministry reported in July that the average life expectancy was a world-record 86.44 years for women and 79.59 years for men.
Authorities rang the alarm bell over missing elderly when a birthday call by Tokyo officials to a man believed to be 111 years old instead led to a police search that found his three-decade-old mummified skeleton in his bed.
In another case the remains of a Tokyo woman believed to be 104 were found stuffed into her son's backpack, where they had been for more than a decade.
And earlier this month a 58-year-old woman living near Osaka admitted to keeping her father's corpse hidden at home for the past five years.