What's the Probability that the Next President Will Have Dementia?

With the Democratic primary all but settled, it appears we’ll be seeing a contest between the two oldest candidates for the major parties in a general election. This has stirred up some controversy. Questions have been raised, whether fair or not, about the mental faculties of both Biden and Trump. In particular, what is the probability the person we elect in 2020 will experience dementia while in office and, if so, how much do we have to worry?

As I discuss in my book, How Madness Shaped History, we’ve had at least two presidents who’ve had experience with dementia. The first was Woodrow Wilson, incapacitated in office after a stroke so bad that running the country was largely left to his wife, chief of staff, and physician.

The second was Ronald Reagan. Though diagnosed with Alzheimer’s Disease (AD) after leaving office, speculation has swirled that early AD began during his term in office. AD progresses slowly and often isn’t diagnosed until the symptoms have become noticeably impairing on a day-to-day level. Even Reagan’s children disagree whether he experienced AD while in the White House. Analyses of Reagan’s speech patterns while in office are consistent with those of individuals in the earliest stages of AD, but debate is likely to continue.

Both cases show us potential concerns. The country may end up being run by unelected individuals with personal agendas and, as in the case of the Iran-Contra Affair, an embarrassing fiasco during Reagan’s final term, the results might be disastrous.

Are Trump and Biden showing some decline from their younger years? Part of the difficulty in diagnosing comes in distinguishing dementia from normal age-related brain changes. Though many cognitive abilities remain intact with age, some do decline. Perhaps not surprisingly, these particularly cluster around novel tasks. Older adults may take longer to learn new technical things, may have more trouble forming new memories or paying attention to new tasks. Speech fluency can be reduced somewhat, and older adults’ reaction times may get longer. Individual experiences vary, of course, and none of these normal declines mean that a person can’t be a productive and happy member of society.

Dementia involves cognitive decline in excess of what is expected for normal aging. There are various forms of dementia, each with different symptoms and courses. AD, for example, is well known for the damage it does to memory systems. However, it can also influence mood and decision making and cause paranoia and eventual loss of self-care. Dementia, particularly of the AD type, can be difficult to talk about and acknowledge, as it seems to involve the gradual destruction of the self. Perhaps that’s why we seem to have such trouble talking about it.

Do Trump or Biden have dementia? The occasional mangling of words or flights of association both have demonstrated publicly aren’t enough for such a diagnosis. The good news is that rates of dementia among older adults have fallen in the US. For men in their age category, dementia rates are typically around 10% or so. Milder cognitive impairments not reaching the level of dementia may be more common, in one study closer to 20%.

Thinking in terms of probability calculators, if the probability of either man having dementia is about 10%, the probability that choosing between them will result in a presidency under the influence of dementia is about 19%. If we combine that 10% with the approximately 20% likelihood of milder cognitive impairment for an individual in their age category (thus 30% chance of some impairment overall for each man), the probability that one or both candidates has either mild impairment or dementia goes up to about 51%.

So, without knowing the medical histories of either man, we have a roughly even chance of electing someone with at least mild cognitive impairment, all else being equal.

If we do elect someone with cognitive impairment or even outright AD, how bad is that? The good news is that dementia cases appear to be associated more with loss of an executive’s supervisory authority, leading to cockamamie schemes like Iran-Contra. As compared to other forms of madness (persistence in a behavioral pattern despite obvious destructive consequences to oneself or others), dementia is not typically associated with humanitarian catastrophes. Meaning the dreaded bureaucracy will likely step in and keep things from falling apart. A small comfort perhaps against the madness of kings.