Background: Age-associated increases in medical complexity, frailty, and cognitive impairment may compromise reliable reporting of medical history. Objective: To evaluate the influence of increasing age and cognitive impairment on concordance between reported history of stroke and cerebral infarction, and reported history of diabetes and elevated hemoglobinA1c in community-dwelling older adults. Methods: The association between participant-specific factors and accurate reporting of stroke or diabetes was evaluated using multivariable logistic regression in 1,401 participants enrolled in longitudinal studies of memory and aging, including 425 participants with dementia (30.3%). Stroke and diabetes were selected as index variables as gold standard measures of both were obtained in all participants: magnetic resonance neuroimaging for cerebral infarcts and hemoglobinA1c (≥6.5%) for diabetes. Results: Concordance between reported history of stroke and imaging-confirmed cerebral infarction was low (sensitivity: 17.4%, 8/46; specificity: 97.9%, 799/816). Small infarcts were strongly associated with inaccurate reporting (OR = 265.8; 95% CI: 86.2, 819.4), suggesting that occult/silent infarcts contributed to discordant reporting. Reporting accuracy was higher concerning diabetes (sensitivity: 83.5%, 147/176; specificity: 96.2%, 1100/1143). A history of hypertension (OR = 2.3; 95% CI: 1.3, 4.2), higher hemoglobinA1c (OR = 1.9; 95% CI: 1.5, 2.4), and hemoglobinA1c compatible with impaired glucose tolerance (OR = 3.1; 95% CI 1.8, 5.3) associated with increased odds of discordant reporting. Cognitive impairment and increased age were not independently associated with reliable reporting. Conclusion: Factors beyond advancing age and cognitive impairment appear to drive discordance in reported medical history in older participants. Objective testing for cerebral infarcts or diabetes should be performed when relevant to diagnostic or therapeutic decisions in clinical and research settings.