The goal of this observational study is to explore the optimal dose of computerized cognitive training in patients with cognitive impairment. The main questions it aims to answer are: - Is there an optimal dose of computerized cognitive training for patients with cognitive impairment? - Is the optimal dose different in patients in different age populations? Participants enrolled in the study took a reported computerized cognitive training program and the training data were analyzed for exploring the optimal dose. The researchers will compare the different dose groups to see if there is an optimal dose for the highest improvement in cognitive abilities. The researchers will additionally compare two age groups (aged younger than 60y or aged 60y and older) to see if the optimal doses in the two groups are different.