Having More Than Two Children Can Cause Cognitive Decline

Having three or more children, as opposed to two, has a negative effect on late-life cognition.

As of 2020, the average American family has 1.93 children. Still, having more children than the norm isn’t unusual, with about 38% of mothers aged 40 to 44 having had 3 or more children.

Having three or more kids has its positives and negatives. There will be more energy in the house, your kids will never be lonely, and it might be more fun. However, it will be more expensive, you will get less sleep, and it might be more stressful. Additionally, recent research suggests that it might even put you at risk of cognitive decline.

Study Links High Fertility to Cognitive Decline

A recent study from Columbia University Mailman School of Public Health, the Robert Butler Columbia Aging Center, and Université Paris-Dauphine – PSL discovered that having three or more children versus two has a negative effect on late-life cognition. The data also showed that this effect was greatest in Northern Europe, where higher fertility reduces financial resources but does not improve social resources. This is the first study to look at the impact of high fertility on late-life cognition.

Until now, fertility has gotten little attention as a possible predictor of late-life cognition when compared to other characteristics such as education or career. The results were published in the journal Demography.

“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,” said Vegard Skirbekk, Ph.D., professor of population and family health at Columbia Mailman School. “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,” said Eric Bonsang, Ph.D., professor of economics at the Université Paris-Dauphine – PSL.

The researchers examined data from the Survey of Health, Aging, and Retirement in Europe (SHARE) to see how having three or more children compared to two children impacts late-life cognition. SHARE collects data from representative samples of older people in 20 European countries and Israel, including Austria, Belgium, Croatia, the Czech Republic, Denmark, Estonia, France, Germany, Greece, Hungary, Italy, Luxembourg, the Netherlands, Poland, Portugal, Slovenia, Spain, Sweden, and Switzerland. Participants had to be at least 65 years old and have at least two biological children.

Based on advanced econometric methods able to disentangle causality from simple associations, the evidence suggests that having three or more versus two children is related to worse late-life cognition. They also found that this effect is similar for both men and women.

Pathways Linking Fertility and Cognitive Decline

Fertility may affect late-life cognition via several pathways. First, having an additional child often incurs considerable financial costs, reduces family income, and increases the likelihood of falling below the poverty line, thus decreasing the standard of living for all family members and possibly causing financial worries and uncertainties, which could contribute to cognitive deterioration.

Second, having an additional child is causally related to women’s lower labor market participation, fewer hours worked, and lower earnings. In turn, labor force participation — compared with retirement — positively affects cognitive functioning among men and women.

Third, having children decreases the risk of social isolation among older individuals which is a key risk factor for cognitive impairment and dementia, and often raises the level of social interaction and support, which can be protective against cognitive decline at older ages.

Finally, having children can be stressful, affect health risk behaviors and adversely affect adult cognitive development. Parents with more children can experience more stress, have less time to relax, and invest in cognitively stimulating leisure activities. This can imply sleep deprivation for the parent.

Cognitive Impact Equivalent to Years of Aging

“The negative effect of having three or more children on cognitive functioning is not negligible, it is equivalent to 6.2 years of aging,” noted Bonsang. It suggests that the decrease in the proportion of Europeans having three or more children may have positive implications for the cognitive health of the older population.

“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,” observed Skirbekk. “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 was supported by the Health Chair—a joint initiative by PSL, Université Paris-Dauphine, ENSAE, MGEN, and ISTYA under the aegis of the Fondation du Risque (FDR).

Reference: “Does Childbearing Affect Cognitive Health in Later Life? Evidence From an Instrumental Variable Approach” by Eric Bonsang and Vegard Skirbekk, 1 June 2022, Demography.
DOI: 10.1215/00703370-9930490

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