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How Much Does Behavior Matter to Health? A Quickie
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Can be quite substantial. Jump off the Empire State Building and see for yourself. But, beyond that, the question remains how much of the variation in health outcomes and longevity can be explained by behavioral variation? Well, we don’t quite know. But we do have evidence which indicates that – at least in the developed world – that fraction is quite small.

Here’s I’ll post a series of tweets I made on the subject. Much of the matter is discussed in my post IQ and Death (see also my post “Squid Ink”).

On the matter of the attenuation of the association of IQ/simple reaction time with health/longevity, I’ll quote a few passages on that from relevant papers:

From Ian J. Deary & Geoff Der (2005) Reaction Time Explains IQ’s Association With Death:

After AH4 scores and each of the reaction time measures were adjusted for sex, smoking status, social class, and years of education, all effects remained significant, and the hazard ratios were only slightly attenuated (Table 1). Thus, the relation between IQ and mortality in this sample was not substantially mediated by social class, education, or smoking. Nor was the relation between reaction times and mortality substantially mediated by these variables.

From Batty & Deary et al (2008) IQ in late adolescence/early adulthood, risk factors in middle age and later all-cause mortality in men: the Vietnam Experience Study:

we adjusted for a range of physiological, behavioural, psychological and social risk factors that can be considered as mediating variables in the IQ–mortality relation. The influence of controlling for these factors can be broadly divided into three strata. In the first, despite being associated with both IQ and mortality, adjusting individually for marital status, alcohol consumption, systolic and diastolic blood pressure, pulse rate, blood glucose, body mass index and psychiatric and somatic illness at medical examination had very little, if any, impact on the age-adjusted IQ–death relation (<10% attenuation in risk)

From Hagger-Johnson, Deary, Batty, et al (2014) Reaction Time and Mortality from the Major Causes of Death: The NHANES-III Study:

In fully adjusted models which also adjusted for educational attainment, occupational grade, poverty/income ratio, health behaviors and CVD risk factors, the association was attenuated but remained statistically significant for all-cause mortality (HR = 1.15, 95% CI 1.02,1.29; 37% attenuation), and CVD mortality (HR = 1.22, 95% CI 1.15,1.29; 36% attenuation).

The 2014 study found some attenuation when “health behaviors,” among other things, were factored in. Nonetheless, the association remained. A key problem, however, is that “health behaviors” were gauged via self-report. This has been demonstrated to be highly (though by no means completely) inaccurate. The effect of the measurement error in assessing behaviors in the study is unknown; it could bias the attenuation either upwards or downwards. Another similar study by Deary et al (2008) found that the association between simple reaction time and deaths from cardiovascular disease (and stroke in particular) unaffected by adjusting for covariants (they did however find that the association between reaction time and IQ and deaths from coronary artery disease in particular become non-significant when “health behaviors” were factored in). However, these health behaviors were also assessed by self-report. Yet another study by Shipley, Der, & Deary et al (2006) looked at a British sample (N ~7,400) found the association with simple reaction time and all cause mortality. The effect was also mediated by variables. These results call for a meta-analysis.

I also threw out this idea today:

The idea is that some ailments do appear to be heritable (e.g., heart disease), however, may have pathogenic involvement. A (heritable) weaker immune response or otherwise compromised defensive capacity might then at least partly explain observed heritability of these diseases.




(Republished from JayMan's Blog by permission of author or representative)
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  1. Sisyphean says: • Website

    Fit people often say to others: “Behave like me and you will be as fit as I am.” unfortunately they forget to mention that to behave like they do requires patience, commitment, willingness to experiment, and willingness to accept when things aren’t working and make changes to make them work. Those are a lot of cognitive and emotional hurdles.

    This is why I like to say that it’s both true that all diets work and that all diets fail. If you can make it over those hurdles it doesn’t matter which diet you choose, you’ll keep going until you reach your goal. If you can’t make it over the hurdles, there’s no diet good enough to help you. The dieter is the key, not the diet.

    Of course, this reality doesn’t sell many diet books.

    • Replies: @JayMan
    , @Sisyphean
  2. JayMan says: • Website


    I think it’s fallacious to say that everyone has something out there that work for them, even in principle.

  3. Sisyphean says: • Website

    I didn’t mean to imply that. There are definitely people who can’t make any of the hurdles and will never be able to achieve a lean physique unless they were to live in a starvation environment devoid of any extra calories, which might very well mean those people are better adapted to such an environment, but I digress. However the fact that it’s fallacious doesn’t stop people from peddling solutions for everyone, it’s hard to make money saying: “Hey all you super dedicated people who chance has caused to gain a few extra pounds, pick up this routine that you will surely be able to stick to and you’ll lean out in no time!” What is that, like 5% of dieters?

  4. jjbees says:

    There is no evidence that diets even work outside of the South Beach Concentration Camp diet.

  5. Wasn’t there something in the news in the last few weeks about propensity to working out etc being heritable?

    • Replies: @JayMan
  6. JayMan says: • Website

    @Foolish Reporter:

    There sure was. I found an older meta-analysis that spanned the Western world that found the same. Self-report, though, so take that for what it’s worth.

    • Replies: @FoolishReporter
  7. Anonymous • Disclaimer says: • Website

    I’m a little confused, mainly because I don’t understand your Tweats. Isn’t smoking a “behavior?” Doesn’t quitting smoking — something which almost all my friends have done — improve health and longevity?

    • Replies: @JayMan
    , @elijahlarmstrong
  8. JayMan says: • Website


    That’s the thing, it doesn’t. It took me by surprise, but turns out large RCTs find that quitting smoking does nothing for longevity (at least during the study).

  9. @JayMan

    good deal. nice write-up as always!

  10. Anonymous • Disclaimer says:

    Have you heard about the Klotho gene. A variant of it in the heterozygous form increases intelligence at all ages and is associated with longevity–especially by decreasing the risk from cardiovascular disease. It may be the major gene for intelligence that Volkmar Weisse has always said would be found.

    • Replies: @JayMan
    , @elijahlarmstrong
  11. JayMan says: • Website

    @David Benson:

    Likely a false positive like most of these purported hits. Let’s wait for the BGI results.

  12. panjoomby says:

    I agree with you. any explanations/refutations for Finch & Tanzi (1997), & Herskind, McGue, Holm, Sorensen, Harvald, & Vaupel (1996), where the party line for 20 years has been “(‘only’) about 25% of the variability in lifespan among twins is genetic” – is that perhaps a restriction in range problem attenuating the h-squared heritability?

  13. Anonymous • Disclaimer says:

    Thought: part of the reason low IQ people have poorer health is not just genetic load, but reduced ability to fight pathogens cc @johndurant
    9:55 AM – 23 Jul 20


    • Replies: @JayMan
  14. JayMan says: • Website


    My brain. That’s what “thought” signified. It’s speculation that I need to follow up on.

  15. Reblogged this on Philosophies of a Disenchanted Scholar and commented:
    The wonderful world of RT tests, I know it well.

  16. elijahlarmstrong says: • Website

    What???????? That makes no sense. I mean, something like two-thirds of smokers will have lung cancer in their lifetime. Is the general population rate that high? Even the general low-IQ population rate?

    • Replies: @JayMan
  17. elijahlarmstrong says: • Website

    There is almost certainly no major gene for intelligence. It would have been found already.

  18. JayMan says: • Website


    Actually, the lifetime incidence of lung cancer for heavy smokers is only 25%. Odds are still pretty good for the average smoker.

    I don’t know what’s going on there. But it’s certainly not as clear as we’ve been led to believe.

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