A death is classified as premature in cases where it occurs earlier than the projected lifespan of a given age group. Therefore the earlier the death, the greater the years of life lost. The years of life lost figure is calculated by aggregating the differences between the actual and projected average lifespans of persons at the time of deaths taking into account their gender, age and other factors.
Surm loetakse enneaegseks, kui see saabub enne vanuserühma eeldatava eluea lõppu. Seega, mida nooremas eas surrakse, seda suurem on eluaastate kaotus. Näitaja arvutamiseks summeeritakse soo, vanuse ning vajadusel ka muude tunnuste lõikes isikute surma hetke vanuse ja sellele vanusele vastava eeldatava eluea erinevused.