Objectives To examine the effect of cardiovascular and metabolic diseases on initial cognitive test performance and rate of change in three cognitive measures. Design Prospective cohort study. Setting General practices in six towns throughout Germany. Participants Three thousand three hundred twenty-seven participants aged 75 and older (average 79.7 ± 3.6). Measurements Data were collected during home visits every 18 months and included sociodemographic variables, depression, disease status, drug intake, and cognition. Results Although the presence of transient ischemic attack (TIA) or stroke and diabetes mellitus was related to poor initial cognitive test performance, the presence of those and other far-reaching chronic diseases or a higher disease burden were not related to the rate of change in cognition over time. Conclusion Diabetes mellitus, stroke and TIA affect cognitive test performance beyond well-known sociodemographic variables and depressive symptoms, although none of these diseases contributed to cognitive decline over time. In practical terms, prevention and diagnosis of cardiovascular and metabolic diseases may be essential to cognitively healthy aging.