Three’s a crowd: Having more than 2 kids linked to weaker brain function

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NEW YORK — Everything in moderation — even kids? Researchers from Columbia University and Université Paris-Dauphine report having more than two kids may have a negative impact on late-life cognition. The study shows that older parents with just two children appeared sharper cognitively than those with three.

The connection between kids and cognition was particularly strong among parents in northern Europe. This is noteworthy because, in those countries, having a lot of children usually decreases financial resources without necessarily improving social resources.

While prior studies have focused on the effect of other factors, like education or career choices, on lifelong cognitive outcomes, this is the first project ever to investigate the influence of high fertility.

“Understanding the factors that contribute to optimal late-life cognition is essential for ensuring successful aging at the individual and societal levels—particularly in Europe, where family sizes have shrunk and populations are aging rapidly,” says Vegard Skirbekk, PhD, professor of population and Family health at Columbia Mailman School, in a university release.

“For individuals, late life cognitive health is essential for maintaining independence and being socially active and productive in late life. For societies, ensuring the cognitive health of the older population is essential for extending work lives and reducing health care costs and care needs,” adds Eric Bonsang, PhD, professor of economics at the Université Paris-Dauphine.

More mouths to feed leads to less money

To investigate whether or not having three or more children versus two children affects late-life cognition, study authors analyzed data provided by the Survey of Health, Aging and Retirement in Europe (SHARE). Featuring representative samples of the older populations across 20 European countries and Israel, SHARE was an ideal match for this project. Each individual was at least 65 years-old and had at least two biological children.

Via a series of complex econometric methods, the research team was able to successfully disentangle various causal relationships from simple associations. In simpler terms, the analysis found that having three or more kids (as opposed to just two) is related to worse late-life cognition. This held up among both moms and dads.

Why do more kids lead to potential cognitive decline? Researchers can’t say for now but point to a few different possibilities and contradictions.

To start, more kids mean spending more money — which leads to a lower overall family income and increased chances of falling below the poverty line. Such a sequence of events would lower the standard of living for all family members, not to mention cause constant financial anxiety. All of this, hypothetically, can contribute mightily to late-life cognition drop offs.

Having more kids is also causally related to women’s lower labor market participation, fewer hours worked, and lower earnings. That means, in comparison to retirement, remaining on the workforce positively affects cognitive functioning in both men and women.

More kids, less me-time

All of the unavoidable stress that comes along with parenthood can potentially influence cognition as well. Parents with more kids are more likely to be stressed, have less relaxation time, and often complain of sleep deprivation.

What about the social aspects of a family? Paradoxically, having more kids should decrease one’s risk of social isolation as they grow older. More calls, texts, and time spent with loved ones can go a long way toward keeping an aging mind sharp.

“The negative effect of having three or more children on cognitive functioning is not negligible, it is equivalent to 6.2 years of aging,” Dr. Bonsang notes.

“Given the magnitude of the effect, future studies on late-life cognition should also examine fertility as a prognosticator alongside more commonly researched predictors, such as education, occupational experiences, physical exercise, and mental and physical health,” Dr. Skirbekk concludes.

“In addition, future studies should address the potential effects of childlessness or having one child on late-life cognition. We also need more information on the types of interactions, supports, and conflicts that occur between parents and children, which may influence cognitive outcomes.”

The study is published in the journal Demography.

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John Anderer

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  1. People who pop out kid after kid are short in the smarts department from the start.

    1. Like Bobby and Ethel Kennedy? No wait, bad example. How about Teddy Roosevelt… oh wait, another bad large family example…

    2. Just laying the groundwork for “scientific basis” to justify abortions. In the mean time, supporters of the study will die without heirs so that is why they want to take over the education of other people’s kids.

    3. Several methodological issues with this study. First, it is NOT causal. Only correlational. The pattern could be the result of a third variable. Second, fertility is associated with good health, challenging the hypothesis. Third, the birth rate in Northern Europe is so low that high birth rate women have predisposing factors.

  2. When you get too old to work and the social security system collapses, having more children is insurance that, at least, one of them can provide for you.

    1. While also creating more people who will sap the resources of this Social Security, making it run out even faster.

  3. With the effects of that popular medicine over the past couple of years families are guaranteed to be smaller. Sadly that might mean the absence of a breadwinner or two

  4. Lived in CentAm 25 yrs+. Those with many kids, are not too smart, not just in mathematics, yet also in basic things. Providing economic assitance to these people, in anyway, 100+ forms now, is a negative for humanity. Rule.

  5. Good heavens. The author needs to go back to college and take research design and advanced quantitative methods classes. You simply cannot draw CAUSAL relationships from correlational data, no matter what statistical techniques you use. Here is one correction: “The negative effect of having three or more children on cognitive functioning is not negligible, it is equivalent to 6.2 years of aging,” Dr. Bonsang notes. NOT negative effect, negative “association” or negative correlation should be used here. Big difference.

  6. Who would be stupid enough to believe anything coming out of Columbia? Research? They just shill for whoever is the highest bidder no matter the subject! But then most so called places of “higher education” are little different…Columbia just stands out.

  7. I have four children. I speak seven languages. My IQ is over 140.
    I think what they meant to say in the article, is that when high IQ people have fewer children, this is bad for the society.


  8. Modern science at its best, proving what we really want to hear. From a philosophical point of children have always required sacrifice. From career to sanity, yet the “math” all depends on the expectations to begin with. If you plan was to retire and sit around living off your the fruit of your labors, watching the world go by, then this article makes sense. But from a stand point of using your resources to bring human beings into existence and caring for and loving them in all their wonderful messiness, then article reveals the deeper issue at heart. We are selfish and care about our own economic well being than another life. The real math to me is generations down the road when those with two or less children have a small family tree and their children have to find spouses from those having 3 or more. Turns out wisdom has little to do with smarts. Tune in next week for more confusion from “science” on why the birth rate is falling…must be quality of sperm or something.

  9. Correlation vs Causation. Pretty sure this isn’t it. Generally cognition is a skill that must be exercised continuously. That is the highest determining factor. This conclusion seems unscientific it also doesn’t seem vetted.

  10. Just laying the groundwork for “scientific basis” to justify abortions. In the mean time, supporters of the study will die without heirs so that is why they want to take over the education of other people’s kids.

  11. I am the second oldest of nine siblings, all born in 10 1/2 years with no twins. My mother was a RN. She had 5 kids before she quit working to devote her time to us. Dad was a highly accomplished business executive at an industry leading lighting manufacturer. Every child was highly successful in their chosen field. We had good genes and a great upbringing. And, yes, we were Catholic.

  12. Northern European families with 4+ kids most likely belong to groups with a non-European ethnicity whereas people from groups with indigenous north-European ethnicities usually have between 1-3 kids.
    So I believe it’s rather genetics than the number of kids that effect iq and income.
    This should be easy to prove by comparing outliers, ie indigenous European families with many kids vs non-European fabulous with few or no kids.

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