The Continued Eclipse of Heterogeneity in Gerontological Research

After a long history of neglect, diversity among older people and increasing heterogeneity with age are now familiar ideas in gerontological discourse. We take up the question of whether this increased attention is translating into the domain of empirical research. We replicate Nelson and Dannefer's (1992) review of the treatment of age-based variability in gerontological research, the most recent known assessment of the issue. A sample of empirical studies was drawn from six gerontological journals to determine (a) whether measures of within-age variability were reported and/or discussed and (b) if reported, the observed age-based pattern of variability in the outcome(s). The majority of studies neither reported nor discussed age-based variability. Among those that did report, the great majority indicated either stability or increasing variability with age. Observed patterns varied by outcome type. Although a majority of analyses of psychological and social outcomes suggested that variability was stable across age, half of the analyses of biological/health outcomes indicated increasing variability. Overall, very few (3%) of studies suggested decreasing variability. Consistent with earlier reports of studies, researchers continue to focus on average differences between age groups, yet key issues in social gerontology require attention to intra-age variability.