Infection inflicts a persistent decrease in IQ: study with 180,000 participants

http://www.brainprotips.com/infection-inflicts-a-persistent-decrease-in-iq-a-danish-study-with-180000-participants/

by mocha-rain • 11 years ago

83 60 11 years ago

brainprotips.com

demylinateme• 11 years ago

Why do viral infections have a stronger effect on IQ than bacterial?

fleitz• 11 years ago

My guess would be viruses more easily pass the blood/brain barrier?

eru2• 11 years ago

Viruses are also fought differently by the immune system.

IndianAstronaut• 11 years ago

Parasites seem to also have a significant impact on IQ and poverty as well.

http://www.economist.com/node/16479286/print

farresito2• 11 years ago

This sort of news really scare me. Your brain defines who you are and what capabilities you have, and damaging it can completely change you. The brain is very responsible for a big part of your success and losing it can have a big impact in your life.

madaxe_again4• 11 years ago

Cognitive decline happens whether you like it or not, I'm afraid to say.

I've hit my early 30s and I've started noticing that I'm far more prone to inappropriately replaced words, can't memorise long strings of digits as well as I used to be able to, and so-forth.

unclebucknasty7• 11 years ago

I've hit my early 30s and I've started noticing that I'm far more prone...

That's a really young age to have any sort of marked age-related cognitive decline. It might be explained by something else--even something as "simple" as insufficient quality sleep or stress, both of which can wreak havoc on cognitive ability.

melted• 11 years ago

This could be because you're not getting enough sleep (or aren't sleeping well due to e.g. apnea or something). Set up a simple experiment: go to bed 1-1.5 hours earlier than you usually do for a couple of weeks and see if your "cognitive decline" disappears. As you age you might find you need more sleep.

jacquesm6• 11 years ago

I've hit my early 30s and I've started noticing that I'm far more prone to inappropriately replaced words,

Is this an example of that? Did you mean 'placed' or do I mis-understand you?

Udo• 11 years ago

That's way too early in life for signs of cognitive decline. Are you challenging yourself enough? Do you get adequate and deep rest? Are you preoccupied or depressed? Are you keeping yourself healthy? I know, these are personal (and maybe somewhat condescending-sounding) questions - but they're just examples for things that can impact your mental performance.

Generally, the body's ability to take punishment starts to decline in the thirties which can manifest in mental impairment, but someone who's taking good care of themselves should actually enjoy a pretty well-tuned brain. Biologically speaking there should not be enough damage to justify capability deterioration for a long time to come.

All things being equal, I'd say it comes down to the use-it-or-lose it mantra: your brain gets better in areas where it's being used, and atrophies in others where it isn't.

Mental competence is not a hallmark of youth. In fact, problem-solving performance in many fields should go up with experience, and only degrade very late in life when things like ischemic attacks, prions, cellular garbage, and the natural neuronal die-off rate all come into play as significant factors.

wlievens• 11 years ago

Did you perhaps also have children recently? They're an absolute joy, but also tend to make you at least 20% dumber :-)

trimble-alum• 11 years ago

It's possible to push oneself "harder" and regain function ("neuroplasticity"), as evidenced by stroke rehab.

This is why it's vital to do challenging mental exercises like crosswords puzzles, etc. ("use it or lose it.)

Generally though, the article makes sense because the common cell machinery of nerves (which don't divide as much as say intenstine or dermis cells) can be hampered by underlying issues affecting organelles within nerve cells, which then manifests as functional, quantitative deficit at the macro level.

mikekchar• 11 years ago

I'm in my late 40s. Definitely I'm not the same person, cognitively, that I was in my 20s. It's not all bad, though. I'm sure I would score lower in an IQ test, but I'm actually more capable than I was back then. Experience counts for a lot. I can deal with emotional stress much better, or perhaps I can avoid the situations which cause it (more likely). I can see other people's point of view a lot easier now. I can see gradations in judgement, where before everything was black and white.

It sucks to lose the horse power, but I more than make up for it by driving the car in the right direction. I suspect the decline will continue, but in many ways I look forward to what I will be able to accomplish when I'm older.

JohnBooty• 11 years ago

Anecdotally: I'm a week away from turning 39 and I don't feel I've lost any "raw" mental ability, but actual performance has gotten more challenging because I'm pulled in many more directions at once.

Very few people face the same level of obligations at 20 as they will at 30 or 40.

There's also the Dunning-Kruger effect: the better you get at something, the worse you feel you are at it... presumably, all of us have made strides towards mastering our craft in the last 10 or 20 years....

codexjourneys• 11 years ago

I've noticed a decline in memorization capability in my 30s too, and it sometimes takes a little while to remember small details like what I just ate. It's offset by an increase in my ability to make connections between different topics and ideas.

On balance, I'd choose the connection-making brain over the raw-power brain.

MaysonL• 11 years ago

The brain is also quite resilient. I got shot in the head a few decades ago (.22, luckily) with skull fracture and moderate brain damage – mainly a large hole in my visual field, with occasional visual migraines. Intellectually, I seem to have mainly lost a few steps as far as 3d visualizations are concerned, otherwise still about +3 sd IQ.

farresito2• 11 years ago

Glad to hear you are doing so well! Yes, I completely agree with you the power of the brain to heal itself is amazing. I'm also quite excited by what things are coming in the next ten or twenty years. A good diet probably does wonders, too.

I've been suffering from health issues for the past four years. That's why I'm interested in the brain (I suffer from extreme brain fog, and by extreme I really mean extreme; I can't have a conversation with anyone face to face, and I even have some issues when chatting with people. It takes a long time to really think about what I need to say. I still cannot understand how I'm managing to go through college).

madaxe_again4• 11 years ago

Interesting study, but as the authors concede, one can't quite rule out that the causal flow is in the opposite direction to that which they propose - that is, people with lower cognitive ability are more likely to end up with infections, and people with much lower cognitive ability are more likely to end up with severe infections.

I mean, consider people with dementia, sat in their own faeces (at the severely diminished/severe infection end of the scale), or people with lower intellect lower on the socio-economic scale engaging with jobs where they're more likely to end up with infections - construction, handling hazardous waste, etc. etc.

unclebucknasty7• 11 years ago

this reverse association could not account for the observed temporal correlations or the correlations with the severity of infection. Moreover, the correlation between infections and cognitive ability retained significance even after adjustment for other parameters known to influence general cognitive ability...which are also associated with socio-economic gradients.

Could possibly be both.

mocha-rain• 11 years ago

I'm sympathetic to your point of view; in some cases it seems nearly impossible to rigorously exclude reverse-associations when there are so many complexities.

The authors respond to this objection as follows:

The finding that infections are associated with decreased general cognitive ability after a latency period might be an epiphenomenon and not a biologically-mediated relationship. For instance, a reverse association could have existed so that lower cognitive ability may be a risk factor for acquiring infections. Furthermore, studies have indicated that immune related genes might be implicated in cognition [34], and individuals with genetic liability towards a lower general cognitive ability might also be more genetically vulnerable towards infections. However, although a genetic or reverse association could have partly explained some of the observed associations, this probably does not account for the observed temporal associations or the associations with severity of the infection.

The association between infections and cognitive ability remained significant after adjusting for other factors known to influence a decrease of general cognitive ability, such as gestational age, birth weight [35], and having more older siblings (i.e. being later in a sibship), which often correlate with socio-economic gradients [36]. ..Nevertheless, the findings remained significant also after adjustment for an individual or family history of psychiatric disorders and substance abuse which could be associated with several of these unmeasured risk factors as well as socio-economic factors. Furthermore, the possible effect of maternal smoking during pregnancy should to some degree be captured by the included birth weight and gestational age in the adjustments. Moreover, there may be diseases that are associated with both increased susceptibility to infections and somewhat lower cognition (either the disease itself or its treatment).

danieltillett2• 11 years ago

How do the authors manage to just wave away all the genetic effects with just "this probably does not account for the observed temporal association"? Either the authors have some evidence or else it is not a hypothesis that they can rule out. All their correction factors are non-genetic factors.

BoardsOfCanada2• 11 years ago

The p-value (a function used for testing a statistical hypothesis) corresponding to these results was less than 0.001, indicating that the probability that the findings were due to chance alone (or that the null hypothesis is true) is less than 0.1%.

Actually, I think it means that IF the null hypothesis is true, there is only a 0.1% chance that we would get this much deviation (or more) from it due to chance. Which isn't the same thing. Still, seems like a significant result of course, but let's be correct about these things.

eru2• 11 years ago

axonopathy, it seems you are hell-banned for some reason..

solve2• 11 years ago

The whole science industry should follow the lead of those scientific journals who've banned p-values from their publications. P-values just lead to so much confusion and nonsense.

And that's without even considering the scientists who cheat the p-values, which is actually just a tiny part of the problem with p-values.

_-__---• 11 years ago

I think that the outright banning of p-values is not the right way to go. The researchers that misuse them and the reviewers that apparently don't understand them are a much bigger problem than the p-value metric itself.

What's needed is a better understanding of empirical conditional statistics and the application of that understanding to the degign of experiments and the analysis of the results produced therefrom.

gwern• 11 years ago

I left a comment on OP several days ago pointing that out; still hasn't appeared nor has it been fixed. Apparently they don't care about being correct.

bandris• 11 years ago

The correction seems to be there now.

stefantalpalaru• 11 years ago

Here's the scientific article: http://journals.plos.org/plosone/article?id=10.1371/journal....

ExpiredLink• 11 years ago

It's merely correlation, not causation.

P.S.: Why do most articles about the 'brain' try to dumb down people?

danieltillett2• 11 years ago

Interesting study. Intelligence and the immune system share a common property in that they are have a very large number of genes influencing them (several thousand). I would not be surprised if there is quite a bit of overlap in the genes that contibute to both intelligence and immunity. What we might be seeing here is the effect of null mutations in genes that effect both immunity and intellegence.

artnep• 11 years ago

I've only read the abstract, but it looks like the actual effect isn't huge.

People with 10 hospitalizations scored lower by .37 SD = 6 iq points.

felixbraun• 11 years ago

Cognitive ability score (Børge Prien’s Prøve Test) has here been converted to parallel conventional IQ scaling, with a mean of 100 and an SD of 15, to give a more familiar metric of effect size.

I have no idea what 6 points mean in this setting.

abandonliberty2• 11 years ago

I would assume a normal distribution where 68% of the population land between 85 and 115. Or a movement of .4 SD. [0]

Nearly 16% of people would lie between 97 and 103. [1]

It's 40% of a full letter grade[2]

[0]http://en.wikipedia.org/wiki/Standard_deviation [1]http://www.wolframalpha.com/input/?i=area+e%5E%28-1%2F450+%2... [2]http://en.wikipedia.org/wiki/Academic_grading_in_the_United_...

Madmallard• 11 years ago

It's probably not the infection itself, but the fluoroquinolones or other bacteriocidal antibiotics that they give people, that are causing mitochondrial dysfunction in the brain. -_-

gus_massa• 11 years ago

Never thought bout this, but it's clear that it's possible to have an "antibiotic" that target the mitochondria but leave the rest of the cell alive (for a while). That will be a poison, and be not useful as a actual antibiotic. I there a well know substance like this?

leeleelee2• 11 years ago

This is a premature conclusion. There was no measurement of IQ before and after infection, so no such conclusion can be made.

There could be other, unknown, factors that happen to affect BOTH: a person's IQ and their likelihood to be infected, along with severity of infection. For example some genetic, environmental, or other variable that affects your IQ as well as infection-resistance.

It very well might be true, that infection does have the ability to lower IQ. But this study does not prove it.

I wish scientists would be more straightforward about conclusions. The title of the article should read: "Study finds that individuals who have suffered infection have a lower IQ than the general population" or something along those lines. Much different than saying that "infection lowers IQ".

This is beginner-level confusion of causation and correlation.

pdabbadabba• 11 years ago

The title of the article is, in fact "The Association between Infections and General Cognitive Ability in Young Men - A Nationwide Study." And as others have pointed out elsewhere, the authors controlled for some (though not every) conceivable common causes of infection and reduced IQ.

Though, as a criticism of the author of the blog post, I would agree with your comment.

leeleelee2• 11 years ago

Ah, you are correct. I missed that.

Infection inflicts a persistent decrease in IQ: study with 180,000 participants

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