Losing our minds in middle age

When negative stress affects our well-being, we sometimes feel like we are losing our minds...

But when in the lifespan does this really happen? When do we lose our brains?

Until age two we experience rapid growth of brain cells, or neurons. Around that age, rarely used neurons and unneeded connections between neurons (synapses) are reduced. Past research by Hedman, van Haren, Schnack, Kahn, and Hulshoff (2012) suggests that childhood is a time of brain growth, with more neurons being produced. Starting around age thirteen and continuing through adolescence we see brain volume loss as pruning reoccurs so that our brains can be more efficient. Most of young adulthood sees little change in brain volume, but starting at age 35, MRI scans demonstrate a yearly loss of about 0.2% of brain volume. This loss accelerates in older age: in our sixties this increases to a loss of about 0.5% of brain volume every year; this acceleration is often given as one of many explanations for other normal declines associated with aging.

To examine in detail the brain volume loss during the transition to midlife, Guo, Isohanni, Miettunen, Jääskeläinen, Kiviniemi, Nikklinen, Remes, Huhtaniska, Veijola, Jones, and Murray (2016) examined MRI scans of 43 men and 23 women as they aged from their 30s (33-35 years) to their 40s (42-44 years). The participants in this longitudinal study were part of the Northern Finland 1966 Birth Cohort so they should have had similar experiences in their lives as they grew up at the same time. The researchers' goals were to measure overall brain volume at both ages, to identify the locations of any loss as observed in the second MRI performed when the participants were in their 40s, and to clarify any sex differences that emerged.

Total brain volume decline was higher than predicted by past research: on average men lost 3.21% and women lost 4.03%. This sex difference was very small but it reached statistical significance, meaning that the difference was unlikely to be due to chance.

The location of loss also showed a sex difference. After taking into account percentage of total brain loss, Guo et al. found that men lost most of their neurons in the midline areas (specifically: bilateral precentral gyri; bilateral paracingulate gyri; and bilateral supplementary motor cortices). Most of these areas relate to motor skills and one may be involved in decoding certain emotions.

Women's loss was more spread out with most of it occurring in the outer brain (specifically: bilateral frontal parietal; temporal lobe; occipital cortex; cerebellum). These areas relate to language, motor skills, sensory interpretation, vision and visual memories, and emotion association.

Guo et al. did not make guesses beyond a quick mention of hormones as to what caused the sex differences in overall brain loss or the sex differences in loss locations. They also speculated that these differences may translate into differences in midlife men's and women's health or behavior, yet they did not offer any examples.

That leaves us all free to speculate. One bit of demographic information that caught my eye was that the researchers coded participants on "parental leave" as working full-time, because it meant that the participants usually worked full-time but were absent from that work to take care of a newborn child. This made me think about other research related to brain volume and parenting. For example, when women are pregnant their brain volumes can shrink an average 4% and not return to normal volume until about six months after birth. First, that makes the 4.03% decline found in Guo et al.'s female participants sound less ominous: this sort of decline is a normal experience for many women in young adulthood. Second, although most Finnish women in the 1980s usually started having babies at age 29, is it possible that some of the 23 women in this study gave birth just before the second MRI scan? Or is the location of brain loss during pregnancy similar to the location of women's brain loss in the transition to middle age?

Starting in the 80s, Finland offered parental leave to fathers as well as mothers. So it is possible that some of the male participants may have also identified themselves as being on parental leave. However, we know that fathers and mothers often take on different roles in parenting. For example, women are more likely to report that they get up to feed or care for babies in the middle of the night; mothers report more sleep loss than fathers even as children grow older. Poor sleep is associated with brain volume loss in the frontal, temporal, and parietal lobes. Different parental roles and related sleep loss may contribute to women's additional 1% of brain loss; brain volume loss related to poor sleep and brain volume loss related to women's transition to midlife are located in similar areas.

In the end we do not know what is causing these declines or sex differences, and even if we did, at this point we cannot know if these are related to any changes in men's and women's behavior or health as they age. The one thing you can know for sure is that if you are middle aged, pregnant, a new mother, or are sleep-deprived, you ARE losing your mind.

FURTHER READING:

The Guo et al. (2016) article can be accessed online or through your local college library.

Loss of brain cells does not always relate to loss of cognitive functioning. Read an APA Monitor on Psychology article by Melissa Phillips on the strengths of the middle-aged mind.

Childhood trauma can also reduce brain volume. Read a report on trauma's effects on brain development from the Child Welfare Information Gateway (U.S. Dept. of Health and Human Services).

BONUS:

Watch a video from Brown University on Synaptic Pruning:

The Walking Dead: New Parents

I went back to work when my daughter was 7 months old.  Even though I had taught psychology for a long time, the lack of sleep made it hard for me to remember even basic things.  Once I was lecturing on Piaget's stages and for a good 10 seconds I had to stall because instead of the names of the stages all I had in my head was this.  Eventually I remembered the stages; but I have never forgotten that moment.

So this week's blog is dedicated to all of the new parents out there...

First, is this plotting baby correct?  Yes - for the near future.  Newborn babies wake to eat every two or three hours - so in a given night the parents might be awakened four or more times!  A study by McDaniel and Teti (2012) found that one-month old babies wake two to three times each night and three month old babies still wake one to two times each night.  Babies this young require attention at night - to feed them, to soothe their gas pains, to change their diapers, to rock them - so if the baby is awake, that means that the parents aren't sleeping either.

So what is the problem?  Many studies including McDaniel and Teti's demonstrate that getting less sleep tends to go hand in hand with more clinical depression in new parents.  Most, but not all, find that this is especially true for new mothers who are more likely than new fathers to lose sleep caring for Baby's nighttime needs.  We can't be sure that it is only the loss of sleep that is causing the depression; but a positive correlation like this means that it's common to see these two things happening at the same time.

McDaniel and Teti also looked at how lack of sleep might relate to parents' perceptions of each other as parents.  This is important because, "...supportive coparenting, such as when partners endorse and support each others' parenting behaviors and cooperate with each other in raising their children, has been linked to increased relationship quality, less depression, and less parenting stress (p. 886)."  So if parents do not feel like they are a team, that also seems to go hand in hand with depression.

To unravel this riddle, the researchers used data from Project SIESTA (Study of Infants' Emergent Sleep TrAjectories) that included how 132 new parent (heterosexual) couples responded to a questionnaire about coparenting.  The parents rated themselves on how much they agree about parenting, how close they feel to each other and if they fight in front of their baby, their feelings of competition as parents, and how fairly they share the tasks of parenting.  This questionnaire, a measure of parents' depressive symptoms, and reports on their babies' nighttime wakings were collected when the infants were one month old and three months old.

Using a statistical method, McDaniel and Teti were able to determine how these things are related.  Put simply: between one month and three months, babies sleeping less predicted parents sleeping less; parents sleeping less predicted more depression symptoms; more depression symptoms predicted feeling worse about how coparenting is going.  This flow remained the same regardless of the family's social class and the baby's level of fussiness - so even well-off, well-educated families with easy-going babies were likely to show this pattern.

If this sounds miserable (and even more miserable for single parents doing it solo), you may be relieved to learn that most babies are able to sleep through the night by about six months.  Until then, there are some things that you can do to help your baby sleep and ways to make this sleep deprivation even a bit funny (see below) when you feel like a zombie parent.

Further Reading:

Get Your Baby to Sleep: Infant sleep suggestions from pediatrician, Dr. William Sears.  I like that he is clear:  each baby is an individual and each family has its own needs - so choose what feels right for you.

Adam Mansbach wrote a darkly humorous book for ADULTS who are suffering from child-induced sleep deprivation.  Its title and text does contain the F-word so don't click this or buy this book if it would be offensive to you.  Although it is meant to be funny, its angry and defeated tone is probably a good demonstration of depressive symptoms!

You can read the entire McDaniel and Teti (2012) paper here and find out more about Project SIESTA on Douglas Teti's homepage.