Physical activity in midlife not linked to cognitive fitness in later years, long-term study shows

August 24, 2017
PET scan of a human brain with Alzheimer's disease. Credit: public domain

A study led by Johns Hopkins Bloomberg School of Public Health researchers that tracked activity levels of 646 adults over 30 years found that, contrary to previous research, exercise in mid-life was not linked to cognitive fitness in later years.

The finding suggests that may not help maintain cognitive function, or help avoid or delay the onset of the debilitating conditions like and Alzheimer's. Alzheimer's affects as many as 30 million, mostly older people throughout the world. With no known treatment or cure, researchers are trying to identify measures that might help delay Alzheimer's onset or limit its reach.

The study, which appears online in the Journal of Alzheimer's Disease, did find that levels among study participants in the later years were associated with high cognitive function two years later. This supports earlier research findings that exercise may help to maintain cognitive fitness in the short term.

"This study reminds us that physical activity has all sorts of benefits for people, including promoting cardiovascular health, managing optimal weight levels and maintaining bone and muscle mass," says Alden L. Gross, assistant professor in the Bloomberg School's Department of Epidemiology. "Unfortunately it is too early for us to say the same about exercise and Alzheimer's, especially as a possible long-term preventive measure."

There is no known treatment or cure for Alzheimer's or dementia, syndromes that involves declining memory, confusion and eventually limited ability to perform daily tasks. To date, there are no preventive measures, such as physical exercise, brain games or a diet regimen, that have been proven to help delay or altogether prevent its onset. In the US, an estimated five million adults are currently living with Alzheimer's, according to the Centers for Disease Control and Prevention (CDC), and the CDC predicts that this number will rise to 14 million by 2050.

The researchers undertook the study because of a growing consensus that physical activity levels helps prevent Alzheimer's, however much of the evidence for this thinking is based on cross-sectional studies that compare responses from one group of participants with another at a given point in time or within a very short duration, typically several years. Such studies can be valuable for confirming associations, or links, but not at establishing actual causation because of what is known as reverse causation: it is possible that people who eventually develop dementia may reduce their physical activity and exercise as dementia advances. That's where longitudinal studies, which look at the same group of participants over a long time, are more helpful.

The researchers used data from the Johns Hopkins Precursors study, which registered students studying at Johns Hopkins School of Medicine between 1948 and 1964 and tracked them with annual questionnaires about their overall health. The researchers note that the cohort's homogeneity - students at a selective medical school - meant that any differences in physical activity and later cognitive function could not be explained by other differences among participants.

The median age for study participants was 46 years in 1978 and 77 years in 2008. Every several years, the questionnaire asked about exercise, physical activity and physical limitations. The researchers used responses from 1978 through 2008 from 646 participants (598 men, 48 women) to calculate so-called metabolic equivalents, which quantify . Participants were also asked whether they regularly exercise to a sweat.

The team administered cognitive tests in 2008, and, using participants' medical records, scored for dementia through 2011. The researchers identified 28, or 4.5 percent of the cohort, to have Alzheimer's.

No physical activity measure in mid-life was associated with late-life cognitive fitness or onset of dementia. The study confirmed findings of other cross-sectional studies, that higher levels of physical activity and exercise measured close in time to the cognitive testing were associated with better . The authors also looked at whether patterns of change in physical over the life span were associated with cognitive health and found no relationships.

The idea that exercise might play a role in preventing or limiting Alzheimer's makes sense, the researchers say, because physical activity, at least in mouse models, has shown less accumulation of B-amyloid plaques, which are thought to play a role in dementia, including Alzheimer's. In addition, physical activity improves blood flow to the brain, which is linked to better cognitive performance. This may explain why studies find that may contribute to cognitive fitness in the short term.

"These findings have implications for intervention work moving forward," says Gross. "We still need to focus on causes and mechanisms of Alzheimer's and dementia, since we don't yet know which preventive measures may or may not work. For now, when I speak in the community about Alzheimer's, I find that people take some relief in understanding that there wasn't anything that anyone might have done to avoid a loved one developing Alzheimer's. Of course, the goal for is to identify factors that may help older people maintain their cognitive function into their later years. More long-term studies like the Precursors study are needed."

Explore further: How physical exercise prevents dementia

More information: Physical Activity in Midlife is not Associated with Cognitive Health in Later Life Among Cognitively Normal Older Adults, Journal of Alzheimer's Disease (2017).

Related Stories

How physical exercise prevents dementia

July 21, 2017
Numerous studies have shown that physical exercise seems beneficial in the prevention of cognitive impairment and dementia in old age. Now researchers at Goethe University Frankfurt have explored in one of the first studies ...

Exercise results in larger brain size and lowered dementia risk

August 2, 2016
Using the landmark Framingham Heart Study to assess how physical activity affects the size of the brain and one's risk for developing dementia, UCLA researchers found an association between low physical activity and a higher ...

Exercising can protect the brain from Alzheimer's disease

May 16, 2017
The evidence is clear. Physical activity is associated with a reduced risk of Alzheimer's disease, says a panel of researchers and not-for-profit leaders, led by UBC's Okanagan campus.

Mind-body maximizes benefits of exercise to seniors

August 4, 2017
By 2035, a third of the Canadian population will be over 60 years old. And Kinesiology PhD student Nárlon Boa Sorte Silva wants to make sure every one of them stays active and engaged in life via exercise.

Alzheimer's disease study links brain health and physical activity

June 22, 2017
People at risk for Alzheimer's disease who do more moderate-intensity physical activity, but not light-intensity physical activity, are more likely to have healthy patterns of glucose metabolism in their brain, according ...

Physical activity could combat fatigue, cognitive decline in cancer survivors

July 25, 2017
A new study indicates that cancer patients and survivors have a ready weapon against fatigue and "chemo brain": a brisk walk.

Recommended for you

Study shows video games could cut dementia risk in seniors

November 16, 2017
Could playing video games help keep the brain agile as we age?

New player in Alzheimer's disease pathogenesis identified

November 14, 2017
Scientists at Sanford Burnham Prebys Medical Discovery Institute (SBP) have shown that a protein called membralin is critical for keeping Alzheimer's disease pathology in check. The study, published in Nature Communications, ...

Biomarker may predict early Alzheimer's disease

November 10, 2017
Researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) have identified a peptide that could lead to the early detection of Alzheimer's disease (AD). The discovery, published in Nature Communications, may ...

Smell test challenge suggests clinical benefit for some before development of Alzheimer's

November 10, 2017
Researchers at Columbia University Medical Center (CUMC) and the New York State Psychiatric Institute (NYSPI) may have discovered a way to use a patient's sense of smell to treat Alzheimer's disease before it ever develops. ...

How SORLA protects against Alzheimer's disease

November 7, 2017
Researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) have identified a new protective function for a brain protein genetically linked to Alzheimer's. The findings, published in the Journal of Experimental ...

Saving neurons may offer new approach for treating Alzheimer's disease

November 6, 2017
Treatment with a neuroprotective compound that saves brain cells from dying also prevents the development of depression-like behavior and the later onset of memory and learning problems in a rat model of Alzheimer's disease. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.