若じゃく年ねん性せい認にん知ち症しょうじゃくねんせいにんちしょうMeanings1nounearly-onset dementia; presenile dementiamedicine›Medical term for dementia occurring before old age, typically under 65. Also referred to as 若年認知症.See also: 若年認知症若じゃく年ねん性せい