Abstract
BACKGROUND AND OBJECTIVES: Multimorbidity (2+ chronic conditions) associated with faster cognitive decline among older adults, yet longitudinal evidence from low- and middle-income countries, including Mexico, remains limited. This study examines cohort differences in the annual rate of cognitive decline, measured by global cognitive function scores (GCFS), and tests whether the association between multimorbidity and cognitive decline differs between two cohorts aged 50-60 in 2001 and 2012. RESEARCH DESIGN AND METHODS: We assess two 10-year birth cohorts (Cohort 1: born 1941-1951, n = 5,345 Cohort 2: born 1952-1962, n = 4,378), at 3 time points (Cohort 1: 2001, 2003, and 2012; Cohort 2: 2012, 2015, 2021), at ages 50-60 at baseline. We examine cohort differences in average annual GCFS changes by fitting growth curve models incorporating random intercepts and slopes. RESULTS: Two key findings emerged. First, the earlier cohort (Cohort 1, 2001), experienced a faster average annual rate of decline in GCFS than the recent cohort (Cohort 2, 2012). Second, the link between multimorbidity and cognitive decline did not significantly differ between cohorts net of possible confounders. DISCUSSION AND IMPLICATIONS: Our findings advance our understanding of cohort differences in cognitive decline and how the influence of multimorbidity on cognitive decline has evolved in Mexico. The slower rate of decline among the recent cohort suggests potential improvements in cognitive reserve due to educational improvements. Improvements in healthcare access over the past decades may have mitigated the negative consequences of multimorbidity on cognitive decline, potentially explaining the absence of cohort differences.