Friday, July 22, 2011

Roots of the irrational in American politics: pre-dementia and religion

I've written recently about the role of religion in the reasoning of the GOP base. This is an elephant in the room; pundits will discuss the role of American's exceptional fundamentalism in the context of abortion politics, but not in the context of debt politics. The mainstream media is missing an important ingredient in our political paralysis.

There's another elephant out there, and it will grow over the next ten years. The average American voter will become increasingly demented. Demented people rarely vote of course, but most dementia is the end stage of a very long process. Before a voter is disabled, they will lose the ability to process information, recall all but the most recent events, and adjust their beliefs based on evidence. They will, in other words, become less rational.

How big a factor is this?

We can make some estimates by starting with the end-stage state of clinical demential ...

Prevalence of Dementia in the United States: The Aging, Demographics, and Memory Study

... The prevalence of dementia among individuals aged 71 and older was 13.9%, comprising about 3.4 million individuals in the USA in 2002. The corresponding values for AD were 9.7% and 2.4 million individuals. Dementia prevalence increased with age, from 5.0% of those aged 71–79 years to 37.4% of those aged 90 and older...

... The elderly population (those aged 65 years or older) in the USA is expected to double from approximately 35 million today to more than 70 million by 2030...

Of course these numbers are only a start. What we really want are numbers expressed in percentages of voters, and we want the average disease duration from judgment impairment to disability. Personally I suspect that's about 20 years, but the best data I could find was on a relatively rare and aggressive form of early dementia ...

Pre-dementia clinical stages in presenilin 1 E280A... [Lancet Neurol. 2011] - PubMed result

... Pre-dementia cognitive impairment was defined by a score 2 SD away from normal values in objective cognitive tests, and was subdivided as follows: asymptomatic pre-MCI was defined by an absence of memory complaints and no effect on activities of daily living; symptomatic pre-MCI was defined by a score on the subjective memory complaints checklist higher than the mean and no effect on activities of daily living; and MCI was defined by a score on the subjective memory complaints checklist higher than the mean, with no effect on basic activities of daily living and little or no effect on complex daily activities. De

... Median age at onset was 35 years (95% CI 30-36) for asymptomatic pre-MCI, 38 years (37-40) for symptomatic pre-MCI, 44 years (43-45) for MCI, and 49 years (49-50) for dementia. The median age at death was 59 years (95% CI 58-61). The median time of progression from asymptomatic to symptomatic pre-MCI was 4 years (95% CI 2-8), from symptomatic pre-MCI to MCI was 6 years (4-7), from MCI to dementia was 5 years (4-6), and from dementia to death was 10 years (9-12). The cognitive profile was predominantly amnestic and was associated with multiple domains. Affected domains showed variability in initial stages, with some transient recovery in symptomatic pre-MCI followed by continuous decline.

In this disorder asymptomatic pre-MCI started at age 35, and disability (dementia) at age 50. So the aggressive form has a 15 year course. I would expect less aggressive forms have a longer course, so I'll go with 20 years.

So by these very rough guesstimates about 15% of 50 year old voters will be impacted by "asymptomatic pre-MCI", an early form of cognitive disorder that will impact their judgment. That prevalence will go up with age. Since GOP voters are much older than Dem voters, this, like religious fundamentalism, will be concentrated in the GOP base and it will strongly impact GOP politics.

If you don't understand the two factors of religious fundamentalism and pre-dementia cognitive impairment you will have a hard time understanding the future of the GOP.

No comments: