Diseases of heads of state can affect national policy. Yet, cases of cover-up are numerous and involve not only dictatorships but also open and democratic societies. No system of full disclosure is currently in place to ensure that the public has access to all the information needed to establish whether a candidate to the presidency or an elected leader can discharge the powers and duties of the office. Hence, this essay reviews how the illnesses of democratically elected heads of state have changed history; addresses how to ensure greater transparency, so that leaders will not only be unable to conceal incapacitating disabilities, but also be removed from office once impaired; and lastly discusses how illness does not necessarily imply incapacitation, even though separating the two might often be difficult. These are issues of great relevance to national politics and medical ethics. They are particularly important as the 2020 presidential election is underway, and four out of the five leading candidates are well into their 70s.