['The identification of early markers of dementia is of increasing clinical importance. Recently, impaired mitochondrial function has emerged as a potential marker for age-related diseases and the maintenance of mtDNA copy number is essential for the preservation of mitochondrial function. We investigated the association between mtDNA copy number and cognitive function in elderly women.', 'A total of 107 apparently healthy elderly women were included. Cognitive abilities were assessed using the Mini-Mental State Examination (MMSE). We measured mtDNA copy number in peripheral leukocytes using real-time polymerase chain reaction (PCR) methods. Additionally, cardiometabolic risk factors and physical function were measured.', 'MMSE scores were negatively correlated with the homeostasis model of insulin resistance (HOMA-IR) scores and positively correlated with gait speed as well as mtDNA copy number. After adjusting for age and level of education, the mean values of MMSE scores gradually increased with mtDNA copy number when divided into quartiles. Using step-wise multiple regression analysis, gait speed, mtDNA copy number, and age were determined to be the strongest predictors of MMSE score.'] Is mitochondrial DNA copy number in peripheral blood associated with cognitive function in apparently healthy elderly women?