Differential Item Functioning Along the Old Age Continuum: Contrasting Chronological Age With Contextual Variables in the Assessment of Gains and Losses Across Advanced Old Age

Abstract

Objectives: The fourth age is considered a life stage with a high likelihood of age-related losses. However, very old age extends over decades, and little is known about how transitions that may happen during this age period (e.g., developing support needs or adopting caregiving roles) or lack thereof might change perceptions of age-related gains or losses. Many subjective age scales assume implicitly that they work across advanced old age, but data to support this assumption are scarce. This study reports findings on (1) diverging, age-specific understandings of age-related change and (2) whether very old adults' functional health, received social support, and caregiving roles, rather than chronological age, account for such differences.

Methods: Data came from the nationally representative survey "Old Age in Germany D80+" conducted in 2020/2021, comprising 10,578 individuals aged 80-106 years.

Results: At equivalent levels of perceived gains and losses, adults in the early fourth age reported more "freedom in daily life," less "dependency on others," and fewer "needs to reduce activities," whereas adults in the late fourth age reported more "appreciation of others." Chronological age, as such, was not the primary source of this response shift. Rather, functional health, social support, and caregiving responsibilities accounted for the differences in how older adults interpreted and reported specific age-related gains and losses.

Discussion: Findings underscore that across the multiple decades of the fourth age, interpretations of aging experiences vary and depend on a person's own late-life health and functioning and on that of significant others.

Keywords: Approximate measurement invariance; Developmental shift; Institutionalized population; Representative survey; Very old age.