Temporal Trends in the Level and Decline of Cognition and Disability in an Elderly Population: the PAQUID Study

Abstract

In line with declining trends in dementia incidence, this work thus aimed to compare the cognitive and functional evolution of two "generations" separated by 10 years and to evaluate the impact of specific risk factors on this evolution. This study was conducted on two "generations" of elderly individuals aged 78−88 years, who were included 10 years apart in the Personnes Agées QUID (PAQUID) cohort (France) (n = 612 in 1991−92 and n = 628 in 2001−02) and followed−up for 12 years, with assessments of cognition and disability. Differences between the generations in baseline levels and decline over time were estimated using a joint model to account for differential attrition. Compared with the first generation, the second generation had higher performances at baseline on four cognitive tests (from p < 0.005). Differences in global cognition, verbal fluency, and processing speed, but not in working memory were mostly explained by improvement in educational level. The second generation also exhibited less cognitive decline in verbal fluency and working memory. Regarding disability, we evidenced a lower progression over the follow−up period for the second generation compared to the first one. The cognitive state of this elderly population improved, partially due to improvements in educational level.