What’s true for the body may also be true for the brain. A new study published in Nature Communications found that key structural changes to the brain happen at certain pivotal turning points across the life span.
“The brain does not develop in a steady, linear pattern across the lifespan. Instead, the way the brain changes fluctuates with age,” says lead study author Alexa Mousley, PhD, a postdoctoral neuroscience researcher at Cambridge in England.
Dr. Mousley and her team found distinct reconfigurations of the brain occurring around ages 9, 32, 66, and 83. Many of these turning points align with developmental milestones, she says. For instance, the onset of puberty is around age 9, which lines up with the first structural turning point in the brain.
Another brain turning point, age 66, occurs around the same time people experience a marked rise in the risk of dementia.
Why Does Understanding Age-Related Brain Changes Matter?
A clearer understanding of how the brain changes may one day help healthcare providers identify changes that signal disease, and develop treatments that target the underlying causes.
“The more we learn about the expected changes in brain connections across the lifespan, the better we can recognize what is considered healthy — typical change versus signs of something related to another condition or disorder,” says Mousley.
The Brain Goes Through 5 Distinct ‘Eras’
For the analysis, scientists with Cambridge’s MRC Cognition and Brain Sciences Unit examined MRI brain scans of nearly 4,000 people between ages 0 and 90. The scans produce diffusion imaging, which maps neural connections by tracking how water molecules move through brain tissue.
Comparison of the scans revealed five major periods of brain structure, and four turning points over the course of a human life, as our brains rewire to support different ways of thinking that occur as we grow, mature, and ultimately decline.
The researchers described these eras of the brain as:
Childhood (Ages 0–9)
The brain goes through a period of “network consolidation.” The brain overproduces, then whittles down connectors between neurons (also called synapses), with the more active ones surviving. This consolidation and refinement happens in the same pattern from birth until about 9 years old.
Adolescence (Ages 9–32)
White matter (a large network of nerve fibers that help information travel between different areas of the brain) continues to grow in volume. The increasing efficiency of these white matter highways means the brain gets better at coordination and and sharing information to support cognitive functions and consciousness.
Typically, this transitional phase between childhood and adulthood is thought to start around age 10 and end by the mid-twenties. When it comes to the brain, though, the timeframe of adolescence appears to be longer.
“Based purely on neural architecture, we found that adolescent-like changes in brain structure end around the early thirties,” says Mousley. “Our work shows that the pattern of brain rewiring is consistent between 9 and 32 years old.”
While cognitive performance generally increases during this stage, so does the risk of mental health disorders.
“From previous work, we know that around two-thirds of people who will have a mental health disorder develop it before age 25, with most emerging around age 15,” says Mousley. “So it’s a reasonable hypothesis that changes in structural patterns might be related to increasing risk of mental health disorders.”
Adulthood (Ages 32–66)
Compared with rapid maturation in earlier life, brain network development slows during this period, which is the longest stretch without any major change. This period of stability also corresponds with a plateau in intelligence and personality.
Although not explored in the study, this stabilization corresponds with a time in life when we may be more prepared to take on adult responsibilities.
“Even though we’re not seeing dramatic cognitive ‘growth spurts’ during these decades, the brain’s stability supports the kind of mental efficiency needed for managing careers, parenting, relationships and all the daily ‘adulting’ tasks,” says Dana R. Connor, PhD, a neuropsychologist with Henry Ford Health in Detroit, who was not involved in the study. “In fact, people often describe their thirties through fifties as the years when they feel most confident and capable.”
Early Aging (Ages 66–83)
At this stage, some of the connections in the brain weaken, and the brain as a whole becomes more separated into small, well-connected groups of regions compared with earlier in life.
Mousley says it’s not clear if the restructuring of this era corresponds with potential degeneration of the brain, which might explain the increase in dementia risk at this age.
Dr. Connor says brain changes at this age may translate into changes in thinking ability. “People at this age may process information a bit more slowly, need a few more repetitions to learn new things, take a few seconds longer to recall a name or rely more on lists and routines,” she says. “These are considered normal, age-related changes and are not signs of a brain disease or dementia.”
Late Aging (Ages 83–90)
Brain structure enters a final era as connectivity further declines. There is a noticeable shift in brain regions, moving away from “global” processing (perceiving the overall picture) to “local” (focusing on more specific components or details).
The Brain’s ‘Adolescent’ Stage Isn’t Over Until Age 32
Connor says the new research sheds light on how, and particularly when, the brain goes through “growth spurts” — which had until now not been well-defined.
An unexpected finding was the length of the “adolescent” period, according to Ilana Bennett, PhD, an associate psychology professor at the University of California in Riverside, and a principal investigator at the school’s Laboratory of Aging and Neurocognitive Imaging.
“I am surprised that this adolescent developmental epoch spans such a wide age range, 9 to 32 years old,” says Dr. Bennett, who was not involved in the research.
“There are a lot of emotional, cognitive, and lifestyle changes during this time that I might have expected would create more change during this period.”
A Healthy Lifestyle Can Promote a ‘Younger’ Brain
One of the major limitations to the investigation, according to study authors, was that the research looked at different people at different ages, and did not follow the same people over time, so scientists could not explore the nature of turning points within specific individuals across their lives.
Connor stresses that these patterns don’t always map neatly onto what an individual person experiences with aging.
“Brains are incredibly variable,” she says, explaining they are affected by many factors, including overall health, lifestyle, stress, and life experience. “And even though the brain has natural turning points, it is important to remember that we have a lot of influence over how well we think and feel at every age.”
Regular exercise, a healthy diet, consistent quality sleep, and engaging in mental stimulation have all been shown to boost brain health.
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