Does Ageism Cause Alzheimer’s?

By Neuroskeptic | January 6, 2016 9:13 am

Last month, a neuroscience paper got a lot of attention for reporting that Negative Age Stereotypes Predict Alzheimer’s Disease Biomarkers.

It was greeted by headlines such as:

If you think elderly people are icky, you’re more likely to get Alzheimer’s (Healthline)

Lack of respect for elderly may be fuelling Alzheimer’s epidemic (The Telegraph)

Your attitude about aging may impact how you age (TIME)

The research, published in the journal Psychology and Aging, wasn’t about Alzheimer’s disease per se. Rather, the study claims that holding negative attitudes towards the elderly (ageism) is correlated with the later development of neurobiological changes, or biomarkers, linked to Alzheimer’s. The authors, from Yale University and the National Institute on Aging, were led by Becca Levy.

Levy et al. report that scores on the Attitudes Toward Old People Scale (AOPS) questionnaire predicted later hippocampal atrophy, as measured with structural MRI (n=52), and with the levels of neurofibrillary tangles and amyloid plaques present in the brain post mortem (n=74). All these measures were taken as part of the Baltimore Longitudinal Study of Aging, which is the world’s longest-running aging research project – it started in 1958.ageism_dementiaThese are rather fascinating results. It would be very interesting – not to mention ironic – if ones attitudes towards old people predicted how fast your brain physically degenerated with age.

What makes the claims even more remarkable is the span of time that elapsed between when people completed the attitude questionnaire and when the biomarkers were measured.

Consider that Levy et al. measured hippocampal atrophy 25 years, on average, after people did the AOPS scale. For the tangles and plaques, the average interval was a full 28 years – yet the effect size was far from small: the Cohen’s d was 0.45 comparing low to high AOPS scorers.

That answers to a single 16-item questionnaire substantially predict neuropathological changes nearly 30 years later raises my eyebrows. That’s not to say it’s impossible, but I find it surprising.

So what’s going on here? Could a problem with the statistics have inflated the effect?

On PubPeer a number of issues have been highlighted. For instance, a PubPeer poster points out that the authors used one-tailed statistical tests, which seems unjustified. Using two-tailed tests, the key tangles and plaques result (p = 0.046 one-tailed) is not significant. The hippocampal atrophy finding remains significant, however.

Even if the effect is real, it’s a correlation, and doesn’t mean that ageism causes any biological changes. Nonetheless, Levy et al. state that

Several factors support our assumption that negative age stereotypes contributed to the Alzheimer’s disease biomarkers, rather than the reverse direction.

That Alzheimer’s biomarkers cause ageism does indeed seem unlikely. Yet the authors don’t discuss the possibility that both of these phenomena are caused by a third, confounding factor – a covariate that wasn’t controlled for.

For example, socioeconomic status or income could explain these results, if richer people are less likely to get Alzheimer’s, and less likely to be ageist. Or family history of Alzheimer’s might be the culprit: it is certainly a risk factor for the disease, and maybe it also causes ageist attitudes (if people assume that all old people suffer dementia like their own relatives did.)

Overall, then, the headlines were misleading, and the results themselves are difficult to interpret.

ResearchBlogging.orgLevy BR, Ferrucci L, Zonderman AB, Slade MD, Troncoso J, & Resnick SM (2015). A Culture-Brain Link: Negative Age Stereotypes Predict Alzheimer’s Disease Biomarkers. Psychology and Aging PMID: 26641877

CATEGORIZED UNDER: media, mental health, papers, select, Top Posts
  • pip010

    heh the good old correlation, causality and interpretation story :)

    • code103

      This article was embarrassing. Mentioning the third factor, saved face. I find it bizarre the writer jumped to socioeconomic status, as their first suggestion..

      • Neuroskeptic

        Embarrassing how? And bizarre why?

    • David Littleboy

      This was my thought as well. Ageism is probably associated with a whole bunch of things (lower educational level, lack if intellectual curiosity, even not doing music (at least around here, older musicians are the most mature musically, and it’s hard to be ageist when you are in awe of blokes in their 80s)) that are also predictive of Alzheimer’s.

  • disqus_xk55NgnmR2

    What is truly embarrassing are those press headlines (Icky? Really? Do
    the elderly have Cooties too?) The paper is certainly making a huge leap with
    the data, but it’s thought provoking nonetheless.

    There seems
    to be quite a few substantial issues with the authors’ assumptions and the
    discussion on pubpeer is very informative. Setting aside study
    limitations, listing socioeconomic status as the potential third factor
    may not be too farfetched of an idea. Perhaps high SES allows greater
    access to education (especially in regards to health, nutrition, &
    future career opportunities), recreational activities (including those
    of the mind), and green neighborhoods, which all contribute to better
    health (and less stress), with the effects extending to the brain. Those
    born into this economic stratum may then witness elder generations who
    are active and sharp (or at least have $$$ for adequate healthcare).
    This would provide them with a more positive outlook on the aging process in
    conjunction with the environmental resources to age well themselves.
    Further, they may go on to marry similar people so that the genetic or
    even epigenetic component is less at play in this population. Of course,
    it could be that high SES just happens to lend greater access to
    education and enriched environments, and isn’t the third factor in of
    itself. Overall, I’ve seen some mixed results concerning how one’s early
    environment contributes to the likelihood of developing Alzheimer’s, in
    addition to shaping our cultural views (or even contributing towards
    our open mindedness), so it’s only something to mull over.

    • Neuroskeptic

      Right. In suggesting SES as a potential third factor I wasn’t claiming that it is is driving these results.

      It’s merely one example of the many possible confounds that could be. The burden of proof is not on me to prove that SES is relevant. The burden of proof is on the authors to prove that nothing is (if they want to claim causation from their correlational study).

  • parradiddle

    Negative age stereotypes could be harboured by people whose own elderly relatives have displayed poor cognitive function. In that case, those people may have gone on to develop similar dysfunction in old age due to a genetic predisposition.

    • Neuroskeptic

      Indeed – that was my thought also.

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About Neuroskeptic

Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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