Misao Okawa, who turns 116 years old on Wednesday, reckons down her longevity to two simple things: sushi and sleep.

The Japanese woman, whose life has spanned across three centuries, eats three meals a day and ensures she always gets eight hours rest a night.

Mrs. Okawa, who has a son, 94, and daughter, 92 four grandchildren and six great-grandchildren, also credits oily fish such as mackerel for her longevity and only went into a care home 18 years ago at the age of 98.

“She insists that her favourite meal is sushi, particularly mackerel on vinegar-steamed rice, and she has it at least once every month," Tomohito Okada, the head of the Kurenai retirement home where she lives, told The Telegraph.

The mother-of-three has been a widow since her husband Yukio passed away in 1931.

Mrs Okawa became the world’s oldest person following the death of 116-year-old Japanese man Jiroemon Kimura on June 12, 2013.