The unemployment rate among young people is rising.
Marriage at a young age is no longer unusual.
He founded a company at a young age.
She became president even at a young age.
若年 means a young age, the opposite end of the age spectrum from 初老, which marks the approach of old age.
juvenile diabetes
premature alopecia; early-onset hair loss
early-onset dementia; presenile dementia
early-onset Alzheimer's disease