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Human brains are getting larger each decade. That's the conclusion of researchers conducting the large Framingham Heart study which has now gone on for 75 years.

Between 1999 and 2019 the researchers conducted MRIs on participants born from the 1930s to the 1970s, with participants having an average age of 57. They found that each decade the brain volume steadily increased, with the brains of people born in the 1970s having 6.6% more volume than those born in the 1930s. Brain surface area increased about 15% in that time.

Brain structures such as white matter, gray matter, and hippocampus (a brain region involved in learning and memory) also increased in size over time. This increase in brain volume clearly shows that environmental factors (e.g., nutrition, education, social), and not just genetic factors, influence brain size.

The researchers thought that a larger brain volume, which signifies brain health,  might be protective against Alzheimer's disease. And that this could explain why the percentage of people (the incidence) of Alzheimer's disease and dementia has gone down over time.

From Medical Xpress: Human brains are getting larger: That may be good news for dementia risk

A new study by researchers at UC Davis Health found human brains are getting larger. Study participants born in the 1970s had 6.6% larger brain volumes and almost 15% larger brain surface area than those born in the 1930s. ...continue reading "Human Brains Are Getting Larger Over Time"

We all know cigarette smoking is bad for our health (for example, higher rates of heart disease, respiratory disease, and cancer), but it also has an effect on our brains. Yup. Research shows it's associated with a decrease in brain size (volume)!

The researchers found that while all levels of daily smoking was associated with a decrease in brain volume, heavy smoking was associated with an even greater decrease in brain size (volume). This is a dose-response relationship.

By the way, this strong association between a history of daily smoking and overall brain volume, gray matter volume, and white matter volume of the brain was also found in other studies.

They also found that even if you stop smoking, you don't get back that missing brain volume. But at least it'll stop further cigarette smoking shrinkage. The researchers point out that this could explain why smoking is linked to increased rates of age-related cognitive decline and Alzheimer's. Yikes!

From Science Daily: Smoking causes brain shrinkage, study finds

Smoking shrinks the brain, according to a study by researchers at Washington University School of Medicine in St. Louis. The good news is that quitting smoking prevents further loss of brain tissue -- but still, stopping smoking doesn't restore the brain to its original size. Since people's brains naturally lose volume with age, smoking effectively causes the brain to age prematurely, the researchers said. ...continue reading "Smoking and Shrinking of the Brain"

A recent study adds to the list of health reasons to try to avoid type 2 diabetes if at all possible, such as making lifestyle changes (e.g. lose weight if overweight, improve diet,  exercise). Earlier studies found that the brain atrophies (decreases in volume) with type 2 diabetes, and that the presence of type 2 diabetes doubles the risk of dementia in older age. Yikes!

Similarly, Australian researchers in the recent study found that type 2 diabetes in older individuals is associated with decline in verbal memory and verbal fluency over a five year period, but the findings suggest that this may start in midlife.  This is because at the start of the study those with type 2 diabetes already showed signs of greater brain atrophy than those without type 2 diabetes. The type 2 diabetes group had "poorer cognitive function" at the start of the study, and then they continued to decline over the 5 year study time, but not at any greater rate than individuals without diabetes. In contrast to the decline in verbal fluency over the 5 year period in the diabetes group, the non-diabetes group actually showed an slight increase in verbal fluency each year.

Of the 705 persons in the study, the average age of the type 2 diabetes group was 68.2 years, while the non-diabetes group was 72.5 years - so can see that the diabetes group was generally younger. [Note that the brain shrinks a little as we age, and it's a normal part of aging, but you want to minimize it. The more "youthful" the brain, the better for cognitive functioning.

From Science Daily: In older people, type 2 diabetes is associated with a decline in brain function over 5 years, study shows

New research published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]) shows that in older people living in the community, type 2 diabetes (T2D) is associated with a decline in verbal memory and fluency over 5 years ...continue reading "Type 2 Diabetes and the Brain"

Another famous long-running study (Framingham Heart Study) finds more bad news for middle-aged coach-potatoes (that is, those who don't exercise or have poor physical fitness). It's an observational study (thus they found an association), but the finding is pretty damn convincing: that poor physical fitness (basically a sedentary life-style) may be linked to a smaller brain size (brain volume) 20 years later. The reason this is significant is because shrinking brain volume means that accelerated brain aging is occurring.

Researcher Nicole Spartano said: "Brain volume is one marker of brain aging. Our brains shrink as we age, and this atrophy is related to cognitive decline and increased risk for dementia. So, this study suggests that people with poor fitness have accelerated brain aging." Bottom line: if you don't get much exercise or lead a sedentary life-style, then increase your activity levels for hopefully better brain health decades later. Just getting out daily (or several times a week) and walking briskly would improve fitness. From Medical Xpress:

Couch potatoes may have smaller brains later in life

Poor physical fitness in middle age may be linked to a smaller brain size 20 years later, according to a study published in the February 10, 2016, online issue of Neurology, the medical journal of the American Academy of Neurology."We found a direct correlation in our study between poor fitness and brain volume decades later, which indicates accelerated brain aging," said study author Nicole Spartano, PhD, with Boston University School of Medicine in Boston.

For the study, 1,583 people enrolled in the Framingham Heart Study, with an average age of 40 and without dementia or heart disease, took a treadmill test. They took another one two decades later, along with MRI brain scans. The researchers also analyzed the results when they excluded participants who developed heart disease or started taking beta blockers to control blood pressure or heart problems; this group had 1,094 people. 

The participants had an average estimated exercise capacity of 39 mL/kg/min, which is also known as peak VO2, or the maximum amount of oxygen the body is capable of using in one minute. Exercise capacity was estimated using the length of time participants were able to exercise on the treadmill before their heart rate reached a certain level. For every eight units lower a person performed on the treadmill test, their brain volume two decades later was smaller, equivalent to two years of accelerated brain aging. When the people with heart disease or those taking beta blockers were excluded, every eight units of lower physical performance was associated with reductions of brain volume equal to one year of accelerated brain aging.

The study also showed that people whose blood pressure and heart rate went up at a higher rate during exercise also were more likely to have smaller brain volumes two decades later. Spartano said that people with poor physical fitness often have higher blood pressure and heart rate responses to low levels of exercise compared to people with better fitness. Spartano noted that the study is observational. It does not prove that poor physical fitness causes a loss of brain volume; it shows the association. (Link to study in journal Neurology.)

Another study providing evidence that the Mediterranean diet is good for the brain. In elderly dementia-free adults (mean age 80 years) - those that generally followed a Mediterranean diet (higher adherence) had a larger brain volume than those not following the Mediterranean diet, as well as more total gray and white matter volume.The difference between the groups is equal to about 5 years of aging.

Having "higher adherence to the Mediterranean diet" in the study meant higher consumption of healthy foods or lower consumption of unhealthy foods. The Mediterranean diet stresses a  high intake of vegetables, legumes, fruits, whole grains, fish, olive oil, and low intake of saturated fatty acids, dairy products, meat, and poultry; and mild to moderate amounts of alcohol. Specifically: Higher fish intake (at least 3 to 5 oz. weekly) and lower meat intake (no more than 3.5 oz. daily) correlated with greater total gray matter volume. Higher fish intake was also associated with "greater mean cortical thickness". From Medical Xpress:

Mediterranean diet may keep your mind healthier in old age

In news that sounds a bit like it came straight from a sci-fi thriller, researchers say that eating too much meat might shrink your brain. On the flip sid e, however, eating healthy foods from the so-called Mediterranean diet may help your brain stay in good shape as you get older, the new study suggests. The researchers said that people over 65 who ate more fish, vegetables, fruit, grains and olive oil had a larger brain volume than a similar group who didn't follow a Mediterranean diet.

"It was encouraging to see that the more you adhere to this Mediterranean diet, the more protection you get against brain atrophy [shrinkage]," said study author Yian Gu, an assistant professor of neuropsychology at Columbia University in New York City. .... But Gu noted that her study's observational findings cannot prove a definitive cause-and-effect relationship between diet and brain volume. The study was only designed to find an association.

Previous research has linked the Mediterranean diet to a lower risk of Alzheimer's disease, the study said. The diet stresses the consumption of vegetables, legumes (beans, peas and lentils), fruits, cereals, fish and monounsaturated fats such as olive oil, the study authors said. The eating plan also includes a low intake of meat, poultry, saturated fats and dairy products, as well as mild to moderate amounts of alcohol, according to the researchers.

For the study, Gu and her colleagues split 674 adults into two groups based on how closely their diets aligned with the Mediterranean diet. Their average age was 80 years. All participants underwent MRI scans of their brains to measure total brain volume and thickness. They also completed questionnaires about their food choices and eating patterns.

The researchers found that brain volumes of those who didn't follow a Mediterranean diet were smaller than those who did. The difference was minor in overall size—equated to about five years of aging, the study authors said. But, more specifically, the investigators found that eating more fish and less meat was associated with even less brain shrinkage. Using the study findings, Gu contended that eating at least 3 to 5 ounces of fish weekly, or no more than 3.5 ounces of meat each day, could protect the brain from shrinkage. She acknowledged that study participants may have inaccurately recalled their food consumption habits in the questionnaires used.

Several recent studies found that air pollution has a negative effect on the brain. This study of elderly women in North Carolina found that long-term exposure to higher levels of air pollution (specifically fine particulate matter smaller than 2.5 micrometers (called PM2.5) resulted in smaller brain volumes (especially the brain's white matter). They studied elderly women (aged 71 to 89), but the findings should be of concern to everyone exposed to high levels of air pollution.  White matter connects brain regions (with nerve fibers that pass signals throughout the brain) and determines how information is processed in the brain. The researchers pointed out that other recent studies reported that high air pollution is linked to cognitive decline and accelerated brain aging. From Futurity:


Exposure to air pollution may have a negative impact on how the brain’s white matter ages. Older women who lived in geographic locations with higher levels of fine particulate matter in ambient air had significantly smaller white matter volumes across a wide range of brain areas, new research shows.

Fine particulate matter is smaller than 2.5 micrometers and is known as PM2.5, a form of pollution that easily enters the lungs and possibly the bloodstream. White matter connects brain regions and determines how information is processed in the brain....“Our study provides convincing evidence that several parts of the aging brain, especially the white matter, are an important target of neurotoxic effects induced by long-term exposure to fine particles in the air.”

The study found that older women ages 71 to 89 who had lived in places with greater PM2.5 exposures had significantly smaller volumes of white matter and that this could not be explained by the geographic region where they lived, their race or ethnic background, socioeconomic status, lifestyle, or medical conditions that may also influence brain volumes.

The researchers performed brain magnetic resonance imaging scans of 1,403 women who are part of the Women’s Health Initiative Memory Study (WHIMS), a nationwide report based at Wake Forest Baptist Medical Center in Winston-Salem, NC. The researchers also used residential histories and air monitoring data to estimate the participants’ exposure to air pollution in the previous six to seven years.

White matter contains nerve fibers and connects brain regions with each other by traveling deep within and passing nerve signals throughout the brain. Gray matter is primarily composed of neuronal cell bodies, dendrites, glial cells, and capillaries. The study did not find impacts from exposure to air pollution in participants’ gray matter.

Another piece of research that shows that eating more fish and less meat plus the Mediterranean diet is beneficial - this time it's linked to larger brain volume and "delaying age-related atrophy of the brain". Perhaps some other beneficial health-related behaviors are also occurring in these groups, but the link with better brain health and more fish, less meat, and Mediterranean diet is consistently occurring in research. From Medscape:

Mediterranean Diet Linked to Larger Brain Volume

Adherence to the Mediterranean diet (MeDi) may prevent brain atrophy in old age, new research suggests.A large cross-sectional study by investigators at Columbia University in New York linked adherence to the MeDI to larger brain volume in an elderly population, suggesting this type of diet has the potential to prevent brain atrophy and, by extension, preserve cognition in the elderly.

"Our study suggests that adhering to MeDi may prevent cognitive decline or AD [Alzheimer's disease] by maintaining the brain structure or delaying aging-related atrophy," said study investigator Yian Gu, PhD. Previous research has linked the MeDi to a reduced risk for AD and slower rates of cognitive decline in the elderly. "

The aim of the current study was to investigate the association between adherence to the MeDi and structural MRI-based measures of both brain volume and cortical thickness among elderly individuals participating in the Washington Heights-Inwood Columbia Aging Project (WHICAP).The study cohort included 674 multiethnic Medicare beneficiaries aged 65 years or older living in an uptown area of New York City andfish who had no signs of dementia.

All participants underwent high-resolution structural MRI as well as assessment of MeDi adherence based on a 61-item food-frequency questionnaire....A higher score (ranging from 0 to 9) indicated better MeDi adherence. The investigators assessed intracranial volume (ICV), total brain volume (TBV), total gray matter volume (TGMV), total white matter volume (TWMV), and cortical thickness (CT).... the investigators found that those with higher MeDi adherence scores (5 to 9) had larger TBV , TGMV, and TWMV compared with those with lower MeDI scores (0 to 4).

Among the 9 food components of MeDi, higher fish intake was associated with larger TGMV, and lower meat intake was associated with both larger TBV and TGMV . Higher fish intake was also associated with higher CT .

Participants who adhered more to a MeDI had larger brain volumes both in gray matter and white matter, said Dr Gu. She also noted that each additional higher MeDi adherence and total brain volume is equivalent to more than 1 year of aging. Dr Gu noted that most of the association was driven by higher intake of fish and lower intake of meat. Potential mechanisms, she said, include anti-inflammatory and/or antioxidative effects, as well as potential slowing of the accumulation of β-amyloid or tau.

Views about exercise and aging have really changed over the last century. Bottom line: walk  - it's good for cognitive health, especially as you age. Try for at least 1 mile per day (1 mile = approx. 20 minutes brisk walk).

From The Atlantic: Walking for a Better Brain

 A “nerve specialist” from New York named J. Leonard Corning said in 1909 that he was opposed to “excessive exercise,” ... He thought that with the “over-cultivation of the physique the mentality suffered.” Corning wrote during a period when experts widely believed that brain cells didn’t regenerate. As a result, graceful aging was in large part a matter of learning to cope with gradually diminishing brain capacity. Modern science has shown that’s not the case; we do generate new brain cells throughout our lives, although the process can become increasingly imperfect and less efficient with age, as it does with much cellular activity.

One of the largest studies ever conducted was on a group of 121,000 nurses, who were surveyed on a wide range of their health and lifestyle habits starting in 1976. The survey was repeated every two years. This established a trove of valuable information, which public-health researchers have been fruitfully mining since. Among them is Rush University assistant professor Jennifer Weuve, who studied the data collected on 18,766 of the nurses, who were then ages 70 to 81, to unearth connections between exercise and cognitive ability. The results, published in The Journal of the American Medical Association, suggested that those who exercised the most—the group that maintained a median level of walking for six hours a week—were 20 percent less likely to show cognitive impairment than those who exercised the least.

Other long-term studies also show that even modest exercise can serve
 as a bulwark against dementia. A study started in 1989 with 299 elderly 
volunteers in the Pittsburgh area tracked mental acuity and exercise habits....The results, published in the journal Neurology, were sweeping and conclusive: Those who walked the most cut in half their risk of developing memory problems. The optimal exercise for cognitive health benefits, the 
researchers concluded, was to walk six to nine miles each week. That’s a mile to a mile and a half a day, without walking on Sundays if you’re inclined to follow Weston’s example of resting on the Sabbath. (This study concluded that walking an additional mile didn’t help all that much.)

A study written up in the Archives of Internal Medicine in 2001 tracked nearly six thousand women ages 65 and older for six to eight years. The women were given a cognitive test at the study’s beginning and end, the results of which were then correlated with how many blocks they walked daily. Those who walked the least had a drop of 24 percent in cognition. Those who walked the most still showed a decline, but of a lesser degree: 17 percent. The results were clear: “Women with higher levels of baseline physical activity were less likely to develop cognitive decline.”

Peter Snyder of Brown University’s Alpert Medical School, who studies the effects of aging on the brain, recently told National Public Radio that “what we’re finding is that of all of these noninvasive ways of intervening, it is exercise that seems to have the most efficacy at this point—more so than nutritional supplements, vitamins and cognitive interventions ... The literature on exercise is just tremendous,” he said.

Indeed, a 20-year-long study in 2010 found that walking just five miles per week “protects the brain structure” over a 10-year period in people with Alzheimer’s disease and in those who exhibit signs of mild cognitive impairment. “The findings showed across the board that greater amounts of physical activity were associated with greater brain volume,” the researchers concluded.

While different studies arrive at moderately different conclusions via various routes, the recent research of dozens of scientists more often than not converges at a single intersection. And that consistently suggests that if you exercise, your brain will be fitter than if you don’t. This applies to the young, those in the prime of their days, and especially to the elderly.

The 20-year 2010 study mentioned above, results from which were released by Cyrus Raji of the University of Pittsburgh, followed 426 older adults, including healthy people along with those showing mild cognitive impairment or the actual onset of Alzheimer’s. Across test subjects, more walking was shown to result in greater brain volume. “Unfortunately, walking is not a cure,” Raji said. “But walking can improve your brain’s resistance to [Alzheimer’s] disease and reduce memory loss over time.”

The study results suggest that the effect of higher levels of omega-3 fatty acids on brain volume is the equivalent of delaying the normal loss of brain cells that comes with aging by one to two years. The researchers suggest that these higher levels can be achieved through diet or the use of supplements (about 1000 mg of EPA + DHA daily, or by eating a portion of fish such as salmon or sardines every day).  From the January 22, 2014 Science Daily:

Can fish oil help preserve brain cells?

People with higher levels of the omega-3 fatty acids found in fish oil may also have larger brain volumes in old age equivalent to preserving one to two years of brain health, according to a study published in the January 22, 2014, online issue of Neurology, the medical journal of the American Academy of Neurology. Shrinking brain volume is a sign of Alzheimer’s disease as well as normal aging.

For the study, the levels of omega-3 fatty acids EPA+DHA in red blood cells were tested in 1,111 women who were part of the Women’s Health Initiative Memory Study. Eight years later, when the women were an average age of 78, MRI scans were taken to measure their brain volume.

Those with higher levels of omega-3s had larger total brain volumes eight years later. Those with twice as high levels of fatty acids (7.5 vs. 3.4 percent) had a 0.7 percent larger brain volume.

Those with higher levels of omega-3s also had a 2.7 percent larger volume in the hippocampus area of the brain, which plays an important role in memory. In Alzheimer’s disease, the hippocampus begins to atrophy even before symptoms appear.