Dementia is increasing in prevalence, and to date has no cure or treatment. One element in improving this situation is using and sharing data more widely to increase the power of research. Further, moving beyond established medical data into big data offers the potential to tap into routinely collected data from both within and outside the health system. In this report, we examine four exemplar data sharing initiatives to better understand data sharing practices in dementia research and recommend the next steps required to move forward, which will require addressing structural issues including aligning incentives and mindsets toward data sharing.