As people age, some changes in memory and thinking are normal, but significant cognitive decline can affect daily life and independence.
A gradual and persistent loss of thinking skills, such as problems with memory performance, may indicate mild cognitive impairment, which can sometimes serve as an early warning sign for conditions like dementia.
Thus, it is important to recognize early signs and take early action to help slow further decline and improve quality of life.
Evidence suggests that certain lifestyle habits, including regular physical activity, can help support brain health during aging. In particular, regular movement has been linked to better memory and improved thinking skills.
Now, a new long-term study suggests an association between greater memory decline and becoming less physically active over time. These findings suggest that the relationship between cognitive decline and physical inactivity may work in both directions.
The study, published in JAMA Network Open using data from the English Longitudinal Study of Ageing (ELSA), indicates that older adults with less favorable memory trajectories spent significantly more time sedentary and less time engaged in light physical activity.
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Previous research has often focused on the role of exercise in protecting brain health and reducing dementia risk. However, these study findings suggest that cognitive decline itself may also contribute to reduced activity levels later in life.
In this cohort study, the research team followed 2,529 adults aged 50 years and older in England over a 17-year period. Participants underwent repeated assessments of episodic memory. This included immediate and delayed word recall tests, as well as verbal fluency tests, such as animal naming tasks.
In addition, participants wore wrist-based accelerometers continuously for 8 days. This enabled the researchers to objectively measure how much time they spent active, sedentary, or asleep. The team defined light daily movement as walking, household chores, or casual activity.
Notably, compared with participants whose memory declined more rapidly, those with more favorable memory trajectories spent roughly 14 additional minutes per day engaged in light physical activity, and around 12 fewer minutes per day sedentary.
Although these differences may appear modest, they accumulated to approximately 1.6 additional hours of light activity per week. Among those aged 70 or older, the difference rose to roughly 2.3 hours per week.
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“The most important takeaway is that lower physical activity at older ages may partly reflect cognitive decline that has already been unfolding over many years,” study author Mikaela Bloomberg, PhD, a Senior Research Fellow in Social Epidemiology and Social Statistics in the Department of Epidemiology and Public Health at University College London and a member of the ELSA study team, told Medical News Today.
“For clinicians and researchers, this means observational links between physical activity and cognitive function need to be interpreted carefully, particularly at older ages, because reverse causation may play an important role,” Bloomberg added.
“For the general public, I would not take this as meaning physical activity is unimportant for brain health, but rather that changes in activity can sometimes be part of the cognitive ageing process itself, rather than simply a cause of later cognitive problems,” she told us.
The researchers note that the strongest differences appeared in light physical activity rather than structured exercise.
This may reflect the reality that many older adults spend relatively little time doing vigorous exercise, making lighter movement more sensitive to early cognitive changes.
The findings also suggest that cognitive decline may gradually interfere with a person’s ability to plan, initiate, or sustain activity. Early memory problems may also coincide with social withdrawal, depressive symptoms, frailty, or reduced independence.
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Bloomberg noted that differences of 10 to 20 minutes of light activity per day can be clinically meaningful for older adults.
“Differences of this size are not trivial,” Bloomberg told MNT. “In our study, they add up to around 1 to 2 hours less light activity per week, and previous observational research suggests that even modest differences in daily activity can be relevant for health and mortality risk in older adults.”
“Any sort of physical activity that you will actually do is good physical activity. For many older adults, light activity may include walking, gardening, household tasks, or simply spending less time sitting. The best activity is something enjoyable and realistic enough to become part of daily life.”
– Mikaela Bloomberg, PhD
Sedentary behavior and physical inactivity have increasingly been linked to poorer health outcomes in older adults, with previous research noting a potential link with dementia.
This study highlights an association with faster memory decline and more time spent sedentary later in life. While growing evidence suggests a link between physical activity and cognitive decline, it is still difficult to determine the direction of the relationship.
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These findings suggest the possibility of reverse causation. This proposes that rather than inactivity causing cognitive decline, emerging cognitive changes may themselves lead people to move less. Additionally, it also suggests a bidirectional relationship, where both factors may negatively reinforce one another.
The researchers suggest this could help explain why declining activity levels are often observed years before a dementia diagnosis.
“These findings support the idea that the relationship is likely bidirectional,” Bloomberg told MNT.
“Physical activity may still matter for cognitive health, but cognitive decline may also shape later activity patterns. So I do think they suggest more caution in how we interpret observational evidence, especially in later life, but they do not mean exercise is irrelevant for dementia risk.”
The researchers suggest caution when interpreting studies linking exercise with reduced dementia risk in older adults. Additionally, they highlight several limitations in their study.
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They add that participants in the accelerometer portion tended to be healthier, wealthier, and more physically active than the wider population, which could have influenced results. They were also predominantly white, potentially limiting generalizability to more diverse populations.
Additionally, while the findings strengthen the idea that brain health and physical activity may influence one another across aging, the study was observational, meaning it cannot prove that cognitive decline directly causes inactivity.
Still, the findings suggest that reduced movement could be an early sign of underlying brain changes rather than an independent cause.
“Reduced physical activity is too nonspecific to serve as a marker of cognitive decline on its own, because it can have many causes, including physical illness, pain, depression, and changes in mobility,” Bloomberg told MNT. “But it may be one part of a broader pattern of changes that could reflect increased cognitive vulnerability in later life.”
As such, it is still advisable for older adults to maintain cognitive and physical activities to support healthy aging.
