Do benefits of physical, mental activity on thinking differ for men and women?

Studies have shown that physical and mental activity help preserve thinking skills and delay dementia. A new study suggests that these benefits may vary for men and women. The study is published in the July 20, 2022, online issue of Neurology®, the medical journal of the American Academy of Neurology.

The study looked at the effects of physical and mental activities, such as reading, going to classes, or playing cards or games, on cognitive reserve in the areas of thinking speed and memory. Cognitive reserve is the buffer that occurs when people have strong thinking skills even when their brains show signs of the underlying changes associated with cognitive impairment and dementia.

"We found that greater physical activity was associated with greater thinking speed reserve in women, but not in men," said study author Judy Pa, PhD, of the University of California, San Diego. "Taking part in more mental activities was associated with greater thinking speed reserve for both men and women."

Greater physical activity was not associated with memory reserve in men or women.

The study involved 758 people with an average age of 76. Some had no thinking or memory problems, some had mild cognitive impairment, and some had dementia. The participants had brain scans and took thinking speed and memory tests. To calculate cognitive reserve, people's thinking tests scores were compared against the changes in the brain associated with dementia, such as the total volume of the hippocampus, a key brain region impacted by Alzheimer's disease.

People were also asked about their usual weekly physical activity. For mental activity, they were asked whether they participated in three types of activities in the past 13 months: reading magazines, newspapers or books; going to classes; and playing cards, games or bingo. They were given one point for each type of activity, for a maximum of three points.

For mental activity, participants averaged 1.4 points. For physical activity, participants took part in an average of at least 15 minutes per week of activities that elevate heart rates such as brisk walking and biking.

Pa said that each additional mental activity people participated in corresponded to 13 fewer years of aging in their processing speed in their thinking skills -- 17 years among men and 10 years among women.

"As we have arguably few-to-no effective treatments for Alzheimer's disease, prevention is crucial. An ounce of prevention is worth a pound of treatment," Pa said. "To know that people could potentially improve their cognitive reserve by taking simple steps such as going to classes at the community center, playing bingo with their friends or spending more time walking or gardening is very exciting."

Pa said that based on the effect sizes seen in the study, a doubling of the amount of physical activity would be equivalent to an estimated 2.75 fewer years of aging when it comes to women's processing speed in their thinking skills.

Researchers also looked at whether the relationship between physical and mental activities and cognitive reserve was affected by the gene that carries the strongest risk for Alzheimer's, called APOE e4. They found that for women, having the gene lessens the effects of the beneficial relationship between physical and mental activities and cognitive reserve.

The study does not prove that physical and mental activities help improve cognitive reserve. It only shows an association.

A limitation of the study was that people reported their own physical and mental activity, so they may not have remembered correctly. Also, structural and societal factors that affect cognitive reserve, such as education, were not measured in the study.

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Changes in the immune system explain why belly fat is bad for thinking

Iowa State researchers have found for the first time that less muscle and more body fat may affect how flexible our thinking gets as we become older, and changes in parts of the immune system could be responsible.

These findings could lead to new treatments that help maintain mental flexibility in aging adults with obesity, sedentary lifestyles, or muscle loss that naturally happens with aging.

The study, led by Auriel Willette, assistant professor of food science and human nutrition, and Brandon Klinedinst, a PhD student in neuroscience, looked at data from more than 4,000 middle-aged to older UK Biobank participants, both men and women. The researchers examined direct measurements of lean muscle mass, abdominal fat, and subcutaneous fat, and how they were related to changes in fluid intelligence over six years.

Willette and Klinedinst discovered people mostly in their 40s and 50s who had higher amounts of fat in their mid-section had worse fluid intelligence as they got older. Greater muscle mass, by contrast, appeared to be a protective factor. These relationships stayed the same even after taking into account chronological age, level of education, and socioeconomic status.

"Chronological age doesn't seem to be a factor in fluid intelligence decreasing over time," Willette said. "It appears to be biological age, which here is the amount of fat and muscle."

Generally, people begin to gain fat and lose lean muscle once they hit middle age, a trend that continues as they get older. To overcome this, implementing exercise routines to maintain lean muscle becomes more important. Klinedinst said exercising, especially resistance training, is essential for middle-aged women, who naturally tend to have less muscle mass than men.

The study also looked at whether or not changes in immune system activity could explain links between fat or muscle and fluid intelligence. Previous studies have shown that people with a higher body mass index (BMI) have more immune system activity in their blood, which activates the immune system in the brain and causes problems with cognition. BMI only takes into account total body mass, so it has not been clear whether fat, muscle, or both jump-start the immune system.

In this study, in women, the entire link between more abdominal fat and worse fluid intelligence was explained by changes in two types of white blood cells: lymphocytes and eosinophils. In men, a completely different type of white blood cell, basophils, explained roughly half of the fat and fluid intelligence link. While muscle mass was protective, the immune system did not seem to play a role.

While the study found correlations between body fat and decreased fluid intelligence, it is unknown at this time if it could increase the risk of Alzheimer's disease.

"Further studies would be needed to see if people with less muscle mass and more fat mass are more likely to develop Alzheimer's disease, and what the role of the immune system is," Klinedinst said.

Starting a New Year's resolution now to work out more and eat healthier may be a good idea, not only for your overall health, but to maintain healthy brain function.

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