“…Claims data, as one type of "big data," have been actively used for medical research by virtue of a large number of cases, a long period of observation, comprehensiveness, and representativeness of data, especially where a national insurance system encompasses the entire population. [1][2][3][4] In stroke research, claims data are increasingly being used for epidemiological, qualityof-care, and cost studies. [5][6][7][8][9][10][11][12][13] However, there are crucial limitations in previous claims data-based studies with respect to identification of stroke cases.…”