Studies suggest that physical activity and cardiovascular fitness are important to
protect the brain against Alzheimer disease, age-related cognitive decline, and the
commonest vascular causes of dementia— atherosclerosis and mini-strokes. Although
the significance of the findings is uncertain, studies suggest that long periods
of sitting are associated with decreased blood flow to the brain—getting up for a
walk every 30 minutes or so can counter this.

A randomized controlled study of exercise training demonstrated that loss of hippocampal
volume in late adulthood (usually about 1% a year) is not inevitable and
can be reversed with moderate-intensity exercise. One year of aerobic exercise
was sufficient for the increased hippocampal volume that is a marker for improved
memory function. A long-term study of nearly 19,500 healthy people found that at
age 70, only 0.8% of study participants were affected with dementia. But by age
85, this proportion increased to 14.8%. After an average follow-up of 25 years, the
study found that those who were most physically fit, based on an exercise treadmill
test when the study began, were about one-third less likely to develop dementia
than those who were the least fit. The authors of the study were careful to point out
that their findings do not prove that staying fit will prevent dementia, but the study
does suggest a strong association between maintaining high physical fitness and
preventing dementia.

Another study evaluated 2,257 physically capable retired men in Hawaii between
the ages of 71 and 93. The research found that men who walked less than 400
meters (a quarter-mile) a day were almost twice as likely to develop Alzheimer or
other forms of dementia as men who walked more than two miles daily. In a similar
study, women aged 70 years and older who participated in higher levels of physical
activity scored better on cognitive performance tests and showed less cognitive decline
than women who were less active. Women who walked at an easy pace for
at least 90 minutes per week (13 minutes a day) had higher cognitive scores than
those who walked less than 40 minutes per week (6 minutes a day). Women with
the highest levels of physical activity had significantly less cognitive decline than
women with the lowest levels of physical activity.

Another study has shown that not only does physical activity slow age-related mental
decline but that it can improve cognition. The study found that previously
sedentary people over age 60 who walked rapidly for 45 minutes three days a week
could significantly improve their mental-processing abilities. The study indicates
that aerobic exercise creates new neurons and connections. A 2016 study found
that the most physically active elderly had less age-related loss of brain volume
than those who were sedentary. A higher volume of gray matter was found among
the most active participants in the study, those who had about 500 calories a day of
extra energy expenditure.
A study of the fitness records of 30,000 Norwegians found that after 10 years, people
who remained fit throughout the period were 40% to 50% less likely to develop
dementia than those who started out and remained unfit.32 Those men and women
who entered middle age out of shape and then gained fitness also equally reduced
their later risk of dementia—more evidence that it is never too late to start and benefit
from exercise.

Most studies on the link between exercise and cognitive health have focused on
aerobic activities such as running. To see if weight training would have similar
results, a study compared brain scans of three groups of women with existing brain
white matter lesions. One group undertook twice a week resistance training, a
second group did once a week resistance training, and a third group just worked on
balance and stretching twice a week. At the end of a year, the twice a week weight
training group improved physical functioning such as walking speed and had less
progressive shrinkage and other signs of damage to their brain white matter than the
other two groups.

A meta-analysis review of 18 previous studies of exercise on cognition published in
the journal Psychological Science noted the following benefits:
• Exercise programs involving both aerobic exercise (walking, running, swimming,
cross-country skiing, bicycling) and strength training produced better
results on cognitive abilities than either one alone.
• Older adults benefit more than younger adults do from physical activity, possibly
because older adults have more to gain as age-related declines become
more prevalent.
• More than 30 minutes of exercise per session produced the greatest benefit, a
finding consistent with many existing guidelines for adults.

One question is, how intense and how long does exercise have to be to gain cognitive
benefits? There is recent evidence from one study that even 10 minutes of very
easy exercise improves immediate brain functioning, as seen in scans and performance
on memory tests. A different study found that a single 30-minute workout
of moderate intensity (70% of maximum effort) also immediately increased brain
activity in areas needed to recall memories of common knowledge, also termed
semantic memory.

Another study contrasted the cognitive benefits of steady walking on a treadmill for
50 minutes three times a week with interval training that consisted of 4 rounds of
high-intensity walking on an inclined treadmill for 4 minutes, followed by 3 minutes
of easy walking. The incline walking was intense enough to boost heart rates
to 90% of each person’s maximum. After only 12 weeks, the high-intensity interval
walkers showed significant improvements in both physical endurance and memory.
This study is consistent with many others that show that the greater the intensity of
physical activity, the greater the gains of physical and cognitive fitness.
However, not every study of physical activity has shown benefits to cognition. A
24-month trial to determine whether a physical activity program results in better
cognitive function, lower risk of mild cognitive impairment (MCI) or dementia, or
both, compared with a health education program, did not result in improvements in
cognitive function.

The 2018 Physical Activity Guidelines Advisory Committee Scientific Report concluded
that there is moderate evidence for an association between greater amounts
of physical activity and better cognition, including performance on academic
achievement tests; better performance on neuropsychological tests, such as those
involving processing speed, memory, and executive function; and decreased risk of

Studies suggest that physical activity is a moderately effective way to improve brain
health. Regular aerobic exercise increases blood flow to the brain and helps to support
the formation of new neural connections. Physical exercise has been shown to
improve attention, reasoning, and components of memory. Aerobic exercise training
can be expected to bring about a slowing of loss or modest gains in cognitive

This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel.