In biochemistry this past week we have been learning about the immune system. This lead me to do a google scholar search on neurobiological diseases. This search turned up a large number of articles on Parkinson’s disease, Alzheimer’s, and Huntington’s disease, which casused me to form the hypothesis that neurological disorders onset are typically later in life (post 40’s). Is my hypothesis way of mark or is there some truth to it?


  1. Dr. Steve says

    Certainly there are many neurological disorders that show up later in life – although Parkinson’s may show up distressingly early (Michale J. Fox), and Huntington’s often kills people in their 40’s (not exactly old age).

    There are many other neurological disorders that show up in early life – glycogen storage diseases, Lesch-Nyhan syndrome, etc. etc. (pick up a pediatric neurology text and see what I mean).

    Then of course there is autism. (let the flame war begin)

  2. chainsaw mary says

    I think your hypothesis might be a bit too broad. While there are many neurological disorders with adult onset, many of these are degenerative. plaque build up, brain atrophy, degeneration of the substantia nigra – these things take time, so you won’t see them in kids.

    However, like Dr Steve stated, the pediatric population has it’s share as well. While he brought up the great example of Lesch-Nyhan, I was thinking more broadly about epilepsy, which frequently has a childhood onset. Also, as previously stated, glycogen storage diseases show up in infants – Niemann-Pick is a nice example.

  3. Christian Burnham says

    Of course- 40+ is the age at which reproductive capability peters out- so it’s also the age where you start getting all the diseases that haven’t been filtered out by your genetics.

    (Disclaimer- I know next to nothing about biology.)

  4. Jeff says

    Neurological disorders are too broad of a subject, it might be a good idea to scrap that hypothesis.

  5. says

    When you just “notice” some potential effect or regularity that maybe has something to it and it’s at the point where you would be willing to kick it around with others, it’s probably best to call it a “conjecture”. Like “theory”, “hypothesis” has (or at least it used to way back when I studied some science) a somewhat stronger meaning in the sciences than it does in its ordinary English meaning.

    There are certainly neurological dieases among the young, so your conjecture probably needs, at the very least, some qualification.

    That said, conjectures are very important, and I applaud you for making it and putting it up for discussion. Bravo!

  6. JH says

    I work very broadly in the field of brain injury, which we define to include all the neurological disorders, and I can say that if you include the de-myelinating diseases, no your hypothesis is not correct: Multiple Sclerosis in particular, as just the most well-recognised one, frequently shows up with devastating consequences in the teens.

  7. Christian Burnham says

    It would be stunning if neurobiological disorders did not increase with age- so I say your hypothesis is correct.

    The question is by how much.

    (Disclaimer- The owls are not who they seem)

  8. says

    Christian @3 has a point. As others have noted, there are all sorts of neurological disorders that manifest themselves at all sorts of ages.

    It does make a priori sense, though, that genetic neurological disorders that (i) are dominantly inherited and (ii) really screw you up would tend to manifest later in life, after one would have had the chance to reproduce. That’s the only way they could avoid being winnowed away by natural selection. My guess is that any dominant and truly horrible neurological genetic diseases, if they appear in young people, would be the result of a new mutation. (I can’t emphasize the “genetic” bit enough. Your conjecture, or at least my spin on it, is irrelevant to neurological diseases that are not genetically determined.)

    But as I say, that’s just a priori bellyscratching. If you think the line of thought worth following, get thee to medline!

  9. Ichthyic says

    if they appear in young people, would be the result of a new mutation. (I can’t emphasize the “genetic” bit enough.

    you can go beyond it and look at epigenetic factors, too, which would be an alternative source aside from a new mutation.

    which, in fact, brings up the point that this particular student might want to watch the PBS special on epigenetics airing on the 16th of this month.

  10. John Morales says

    Naive comment:
    Maybe a factor is that the longer you live, the greater the odds of something going wrong with you?

  11. says

    Harderkid13; I’ll suggest that what you have is not a hypothesis, but an interesting question to use in order to form a hypothesis. As others have said it is a bit vague, and needs to be fleshed out a bit and a more concrete answer given which you can then test.

  12. sailor says

    Did you also come across Picks Disease?
    Apart from the obvious – age equalls opportunity for sickness – I would think age onset would have to do with the cause. As far as the immune system is concerned kids start getting allergies pretty early. But some of the neurological diseases have to do with genes mutating, or attrition of systems over time. In these cases there would be a greater chance for things to go wrong later in life. Then you have things like Korsakoff’s syndrome which is unlikely to effect kids as they just cannot get through enough booze in time.
    You are clearly right in many cases, but that is only a first step to finding out why.

  13. lzerby says

    Remember, neuron tissue does not usually replicate during adulthood. So it is less likely to be a source of disorders due to cancer (that arises from the non-neuron tissue neuroglia, which does not participate in the whole sensory-receptor cycle (at least not to the degree the neurons do). Gene mutation is less likely in neurological tissue because it does not go through mitosis. I would guess that as we age the possibility for gene mutation without mitosis increases (slightly, ever so slightly) and therefore we see older people with neurological disorders more than in younger people.

  14. David Harmon says

    There’s also Tay-Sachs, a genetic condition which kills in infancy.

    You also need to differentiate between different categories of neurological problems. Some (Huntington’s, Tay-Sachs, Parkinsons, and so forth) are primarily genetic (or epigenetic) problems which lead to neurological consequences.

    Others, like autism and dyslexia, are properly developmental disorders, where various irregularities get embedded into the functional structure of the forming brain. Early environmental problems can also disrupt development, as with iodine deficiency and early heavy-metal exposure.

    And just to confuse things, there are cases where later insult and/or injury can mimic any of the above — not just the obvious traumatic damage, but stuff like drug-induced Parkinson’s, or infectious diseases that take sideswipes at the brain.

  15. says

    Alzheimer’s, Parkinson’s, and Huntington’s have a lot of other features in common, including amyloid formation in the central nervous system, and an association with mitochondrial defects.

    While there are amyloidoses with earlier onset (such as Familial Mediterranean Fever), aging could be another cause of amyloid buildup.