|Title of host publication||Encyclopedia of Quality of Life and Well-Being Research|
|Editors||Alex C. Michalos|
|Place of Publication||Dordrecht|
|Publisher||Springer Science+Business Media|
|ISBN (Print)||9789400707528, 9789400707542|
|Publication status||Published - 2014|
Several definitions already exist for the “oldest old” or “fourth age,” which comprises the most elderly of the older generation. One populationbased possibility is to define the transition between the third and fourth age as the chronological age at which 50 %of the birth cohort is no longer alive, which in developed countries, takes place at around 75 years of age (Baltes & Smith, 2003). Being older than 85 years of age is also often used as a delineation.