Background and Objectives The COVID-19 pandemic and related confinement measures have exacerbated health inequalities and posed unique challenges to cognitive aging. This study examined longitudinal changes in cognitive performance and associated factors before and after the COVID-19 pandemic, using data from the Swiss Lc65+ aging study. Research Design and Methods Analyses included participants with complete data across three assessment waves (2016-2024): 412 participants from Cohort 1 (born 1934–1938), 702 from Cohort 2 (born 1939–1943), and 826 from Cohort 3 (born 1944–1948), with women representing 58–63% of each cohort. Cognitive performance was measured using the Mini-Mental State Examination (MMSE). Generalized Estimating Equations were used to evaluate changes in cognition and associations with socioeconomic, psychological, behavioral, and nutritional indicators. Results Significant declines in MMSE scores were observed over time in Cohorts 1 and 2 (p<.001), with a smaller but significant reduction in Cohort 3. The prevalence of global cognitive efficiency deficits increased notably in Cohort 1 (16.5% to 30.6%) and to a lesser extent in Cohort 2, while remaining stable in Cohort 3. Financial assistance for health insurance was associated with cognitive outcomes in several models, although the direction of this association varied across cohorts. Increases in anxiety and apathy were also observed, particularly following the COVID-19 confinement period. Discussion and Implications Findings indicate that the COVID-19 pandemic and confinement period coincided with accelerated cognitive decline and heightened socioeconomic vulnerability among older adults, particularly in the oldest cohort. Results highlight the need for multidimensional public health strategies.