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Comment by sandstrom | Hacker News Reader

For several decades it has been known that myopia (nearsightedness) and intelligence are correlated[1][2]. Initially it was speculated that reading caused nearsightedness, and through that higher intelligence. There is probably some truth to that.

But with modern DNA sequencing techniques researches has found genes that seem to affect both[3][4].

The hypothesis is that one (or a set of) genes affects both eye size growth (myopia is often caused by the eye being "too long") and neocortical size (associated with intelligence).

Although this probably won't surprise anyone in this research field, I recently read about it -- with my non-nearsighted eyes :) -- and found it interesting. So I wanted to share, since it's somewhat related to this topic.

[1] https://jamanetwork.com/journals/jamaophthalmology/article-a...

[2] https://europepmc.org/article/med/2904062

[3] https://www.nature.com/articles/srep45977

[4] https://pubmed.ncbi.nlm.nih.gov/19127804/

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The issue with these types of studies though is that there's no way to really parse out correlation vs causation, either between these two variables or with social factors at large. Especially in this case there was no molecular work done to validate the hits or establish causal pleiotropic effects. The authors are incentivized to tell a story but as readers I think we can be a little more skeptical and evaluate the likelihood of those kinds of claims (there's positive selection on genes that both increase "intelligence" and alter eye shape) versus like, environmental and social factors induce a correlation between needing glasses and reading...

I agree with this…

I don’t think other studies on myopia fit this same narrative. (However I may be wrong!)

Example: https://www.nature.com/articles/s41598-020-65130-w

I thought the increase in nearsightedness originated in kids not playing outside as much (and thereby not focusing their eyes over longer distances) resulting in eyesight that's more attuned to shorter distances.

I've read that the amount of natural light is important, and that the light inside buildings and houses is not sufficient. Children should spend more hours outside.

If you have a light meter (on a camera or phone or standalone) it’s amazing how “dim” even the brightest indoor lights are.

Full flood wash on a stage is nothing compared to the power of the sun.

Some example values here

https://en.wikipedia.org/wiki/Lux#Illuminance

Office lighting: 250-500

Direct sunlight: 32,000-100,000

At least if wikipedia's summary is to be believed, that's one of the less supported of many potential theories. https://en.wikipedia.org/wiki/Myopia#Environmental_factors

Their summary seems to suggest that the biggest factor is exposure to daylight. So then even reading outside ought theoretically protect against nearsightedness.

> People, and children especially, who spend more time doing physical exercise and outdoor play have lower rates of myopia,[30][29][31][32][33] suggesting the increased magnitude and complexity of the visual stimuli encountered during these types of activities decrease myopic progression. There is preliminary evidence that the protective effect of outdoor activities on the development of myopia is due, at least in part, to the effect of long hours of exposure to daylight on the production and the release of retinal dopamine.

That sounds like a fair bit of support to me.

Can’t find it now, but there is also a comparative development study showing myopia and indoor electrification setting in together in different countries. Though that paper speculated blue light content, with a developing eye hard coded to “tune” its length on the assumption of sunlight.

> The near work hypothesis, also referred to as the "use-abuse theory" states that spending time involved in near work strains the intraocular and extraocular muscles. Some studies support the hypothesis, while other studies do not.[3] While an association is present, it is not clearly causal.[3]

This is what I meant. The GP comment included "and thereby not focusing their eyes over longer distances", which I interpreted to be in contrast to spending time indoors and looking at things close to you. So it's not that things far from you are protective, but specifically variety seems to be. So I think we mostly agree.

I played outside all the time when I was younger and here I am with my glasses :)

This is correct and how myopia works. Not because of an increase in natural light. There’s ample evidence for this.

Yes certainly, that (and many other things) are more important factors. I'm not trying to say this is the only (or even a major) cause.

But that doesn't make it less interesting of a fact.

This should be easy to answer: we are not smarter in the recent decades (the opposite is likely true due to the leaded petrol). The natural selection for smartness is too weak in humans (it does not take much brain to reproduce nowadays).

The hypothesis in TFA is much more likely (regular exposure to bright daylight in children)

On the contrary, IQ has been increasing decade-over-decade basically since IQ was invented. So we are smarter in recent decades.

https://en.wikipedia.org/wiki/Flynn_effect

(Though because IQ is standardized around a mean of 100, it's probably more accurate to say that the IQ of people in the past has retroactively gotten lower)

https://www.newscientist.com/article/2311082-leaded-petrol-m...

The flynn effect is well documented. The negative effect of leaded gas on intelligence just means that average IQ "should" have been raising even more throughout the 20th century.

It's considered to have ended (and possibly started reversing) in developed countries starting in the mid 1990s.

Your link even covers it: https://en.wikipedia.org/wiki/Flynn_effect#Possible_end_of_p...

And here I am thinking my perfect eyesight at 45 is a good thing :(

I heard somewhere that the speculation was that the cerebral cortex is physically next to your eyes, so a big brain stunts your eyes... anyone know if there was any truth to that?

> For several decades it has been known that myopia (nearsightedness) and intelligence are correlated[1][2].

Funny, this was also documented in sanskrit medical texts

The last study says “myopic children regardless of their IQ gain better school achievement”. This makes me think the difference is cultural vs genetic.

Does it mean they are more obedient? Not meaning that as a put down, but being good in school has a lot to do with behavior.

I think it's more likely that people treat people who wear glasses like they're smarter, and they feel pressure to live up to that.

Wearing glasses certainly shaped my hobbies - more reading and computer time. On top of that, being nearsighted (pre glasses) made it hard to catch a ball, so less time spent doing sports.

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