By Deep Shukla — Fact checked by Catherine Carver, MPH
A recent study published in the journal Alzheimer’s & Dementia shows that higher levels of moderate-to-vigorous physical activity and daily steps were associated with a lower risk of mild cognitive impairment (MCI) and dementia in women aged 63 and older. In addition, the study found that moderate-to-vigorous intensity steps, but not light-intensity steps, were associated with a lower risk of cognitive decline. This study helps to clarify the intensity of physical activity needed to prevent or delay cognitive decline.
Dr. Raphael Wald, Psy.D., a neuropsychologist at Baptist Health Marcus Neuroscience Institute, said: “This is a way of further confirming what we already knew while stressing the importance of moderate to vigorous exercise. The study also shows that there is no real cap on the cognitive gains that can be had from physical activity. The more you can safely do the more it decreases your risk for cognitive decline.”
Pending replication in subsequent studies, the quantification of the number of daily steps associated with a lower risk of cognitive decline could help develop public health guidelines. Dr. Wald added, “I think this study is particularly helpful as more people are turning to technology to motivate themselves to stay fit. It provides solid numbers that people can strive for in order to have cognitive gains.”
Dementia is a group of neurological conditions characterized by deficits in thinking, remembering and reasoning. The severity of these deficits interferes with typical daily functioning and is more pronounced than the decline in cognitive function observed during healthy aging.
On the other hand, mild cognitive impairment (MCI) is a condition involving deficits in thinking or memory that are, unlike dementia, not severe enough to interfere with daily activities. MCI is often an intermediate phase between typical aging and dementia, but individuals with MCI do not always eventually develop dementia.
Studies suggest that lower physical activity levels and increased sedentary behaviors, such as sitting or reclining, are associated with an increased risk of cognitive decline and dementia. However, most of these studies relied on subjective self-reports and may lack accuracy.
Accelerometers that monitor the intensity of physical activity can provide objective measurements of physical movements performed throughout the day. Notably, accelerometers can provide objective assessments of light physical activity and sedentary behaviors that self-report questionnaires cannot accurately assess. Accelerometers can thus provide a more comprehensive and objective assessment of physical movements during the day than self-reports.
Only a few studies showing a link between physical activity levels and dementia have used accelerometers. Physical activity can be assessed using accelerometers worn around the wrist or the hip, and measurements obtained using each accelerometer can vary.
Moreover, a study found that hip or waist accelerometers provide a more accurate measure of visually counted steps than wrist accelerometers. Unlike hip accelerometers, wrist accelerometers are likely to register hand movements performed while sitting. However, all but one of these studies have used wrist accelerometers. Thus, the findings need to be replicated, showing a link between higher physical activity levels and a lower risk of cognitive decline.
Evidence suggests that women are at a greater risk of dementia than men. For instance, one study found that the lifetime risk of dementia was 20% in women and 10% in men aged 45 years.
Given the elevated risk of dementia in women, the present study used hip accelerometers to assess whether there is a link between physical activity, sedentary behavior, and the risk of cognitive decline and dementia.
The present study consisted of 1,277 women with an average age of 82 enrolled in the Women’s Health Initiative, a long-term study aimed at preventing chronic conditions in postmenopausal women. The participants included in the study did not have symptoms of MCI or dementia at the onset of the study. The researchers also administered annual cognitive assessments via telephone to identify the cases of MCI or probable dementia during the study.
The researchers used hip accelerometers to measure the levels of low-intensity and moderate-to-vigorous physical activity, as well as sedentary behavior. They were also able to differentiate between light-intensity and moderate-to-vigorous-intensity steps using the accelerometer.
Researchers monitored the participants over an average follow-up of 4.2 years, during which 267 individuals were diagnosed with mild cognitive impairment or probable dementia. Higher levels of moderate-to-vigorous physical activity and daily steps were associated with a lower risk of MCI and dementia.
The researchers divided the participant into four equal groups or quartiles based on the performance of each specific physical movement, including light-intensity physical activity, moderate-to-vigorous physical activity, and time spent sitting or reclining.
The participants with moderate-to-vigorous physical activity in the highest quartile, i.e., the group of individuals who engaged in higher levels of moderate-to-vigorous physical activity than 75% of the remaining participants, performed an average of at least 61 minutes of moderate-to-vigorous physical activity daily. In contrast, the lowest quartile, i.e., the bottom 25%, consisted of women who engaged in less than 23 minutes/day of moderate-to-vigorous physical activity.
The participants with moderate-to-vigorous physical activity levels in the highest quartile were at a 36% lower risk of MCI than those in the lowest quartile. The difference in dementia risk was not statistically significant. However, participants in the highest quartile of daily steps (at least 4050 steps/day) were at a 64% lower risk of mild cognitive impairment and 52% lower risk of dementia symptoms than women in the lowest quartile (less than 1867 steps).
This association between moderate-to-vigorous physical activity and daily steps and the risk of MCI and dementia was obtained after taking into account variables such as the risk of cardiovascular disease, physical functioning, and genetic risk of Alzheimer’s disease due to the APOE ε4 gene.
Further analysis revealed that the number of medium-to-vigorous intensity steps was negatively correlated with the risk of MCI but not dementia. Such an association was absent between light-intensity steps and the likelihood of MCI and dementia. Moreover, the levels of sedentary behavior were not associated with MCI and dementia risk.
Dr. Steven Allder, a consultant neurologist at Re: Cognition Health, said:
“It is well accepted that physical activity (PA) is one of three most promising intervention targets for reducing the risk of dementia. What this study added was a focus on women, as they are at the highest risk of old age dementia, measuring PA with accelerometry rather than self-reported and using rigorous clinical criteria for the endpoints of MCI and probable dementia. [..]These results align well with other large studies of PA and dementia risk but where the PA was not so rigorously assessed.”
The researchers also conducted subsequent analyses to rule out the potential role of cognitive decline in causing lower activity levels. They obtained similar results to their main analysis even after excluding the cases of mild cognitive impairment or probable dementia during the first two years of follow-up.
However, the researchers acknowledged that the follow-up duration of 4.2 years was relatively short, and the role of cognitive decline in influencing physical activity cannot be ruled out. Hence, studies with longer follow-up durations are needed. This is especially critical given that the development of dementia may start 20 years before the symptoms become apparent.
The study’s authors also noted that the study population was small and included few Black and Hispanic/Latinx women, thus limiting the generalizability of these results. They added that these results need to be replicated in a larger, more representative study population.
This article originally appeared here and was republished with permission.