Comment by dspillett

> It makes me wonder if literate people can regress to illiterate,

Under normal circumstances for a healthy human, I'd say no, at least directly. Not a scientific analysis of course, but I don't feel reading ability in a language that you use regularly is going to degrade that significantly. A very similar problem might come about through a drop in attention span which is definitely an issue for many these days, but I wouldn't count this as a literacy problem: the written letters/words/sentences/… are not the issue and other things are going to be equally impacted.

For a second+ language, especially if you never got to a particularly fluent state, this is probably quite different - for anecdata I did pretty well at Spanish GCSE then never spoke a word the 32 years before starting to relearn last year. But again I would not really call this a general literacy problem.

One place where you do see literacy fall precipitously is due to mental degradation due to common complications of old age, if you have relatives with dementia you will have seen this first hand. While literacy is only part of a massive problem here, reading and writing abilities are things that fall away relatively quickly for many (presumably due to them being relatively complex operations, and needing conscious concentration rather than being autonomic life-preserving functions).