In this study, we compare the article impact in terms of article usage between open access (OA) and non-open access (Non-OA) articles from both the temporal and spatial perspectives. Articles published in The New England Journal of Medicine (NEJM) were selected as our research objects. Daily article metric data have been tracked and collected from nejm.org and updated every day for over a year. The results of the study confirm the OA usage advantage to a certain extent. OA increases the article views, expands the geographical scope of article readers, and promotes knowledge diffusion. However, the delayed OA policy has no obvious improvement on the OA effects.