Daily steps appear to slow down cognitive decline in those with Alzheimer risk

While it’s not possible to ‘walk off’ Alzheimer’s disease (AD), daily walks may actually slow down cognitive decline in people with elevated baseline amyloid.And the more steps a day, the better—at least up to a point, according to a study in Nature Medicine. “We demonstrated an association between higher physical activity and slower cognitive and functional decline in individuals with elevated baseline amyloid,” the study said. AD is characterized by two hallmark proteins: amyloid and tau. Amyloid accumulates first, followed by tau, which is more toxic to the brain. More specifically, the researchers found that higher physical activity was associated with slower amyloid-related tau accumulation which was associated with slower cognitive decline. “This benefit occurred because physical activity slowed the buildup of tau, which is closely tied to worsening cognitive symptoms,” said study coauthor Jenny Rabin, an associate professor in the Department of Medicine at the University of Toronto.While other studies have found that being physically inactive is a risk factor for AD, not a lot is understood about its relationship with the progression of the disease, effects on AD biomarkers or differences in AD neuropathology burden. The issue is topical because close to half of AD cases globally are attributable to modifiable risk factors such as physical inactivity, the study said. The study used daily step count measures from middle-aged and older adults in the Harvard Aging Brain Study (HABS). HABS is a longitudinal observational study designed to improve the understanding of how ‘normal’ brain aging differs from the earliest preclinical stages of AD in otherwise healthy adults. The researchers noted that steps were used because measuring them has become popular in the general public, and daily step count is a reasonable and convenient measure of physical activity.The study included a cohort from HABS which consisted of individuals with step data and annual cognitive assessments for up to 14 years. Participants were cognitively unimpaired at baseline.A total of 296 people were included in the analyses. At baseline, they had a mean age of 72.3 years, had a mean number of 5,179 steps per day, and 175 (59%) were female. They underwent cognition and function assessments each year they were in HABS. A subset of 241 underwent longitudinal Aβ positron emission tomography (PET) scans and 172 also underwent PET scans.“For amyloid, researchers usually measure it across the entire brain because once amyloid starts to appear in one area, it is usually present in many others too,” she told the Canadian Healthcare Network in an email interview. For tau, the team also scanned the entire brain, but they paid special attention to a region called the inferior temporal cortex. This area is one of the first places where tau tends to accumulate in Alzheimer’s disease and is closely linked to early clinical symptoms.Participants in the study were grouped by daily steps. A total of 53 were categorized as being inactive which was defined as 3,000 steps or fewer; 90 had low activity meaning between 3,001 to 5,000 steps; 85 were moderate at 5,001 to 7,500, and 68 were active and did 7,501 steps or more. The steps were measured using a waistband-mounted pedometer, which was worn for seven consecutive days during waking hours. Steps were only measured at baseline, and were then related to longitudinal brain and cognitive outcomes, Rabin said.How quickly or intensely people walked was not captured in the study, she said.“There was a significant interaction between lower baseline physical activity and elevated Aβ on greater initial inferior temporal tau burden,” even after various other factors were taken into account, the study said.The tool used to measure cognition was the Preclinical Alzheimer Cognitive Composite-5 (PACC5). Rabin explained that this “is a composite measure of cognition derived from several neuropsychological tests that assess episodic memory, executive function, and global cognition.”The key takeaway from this study is that among people showing the earliest signs of Alzheimer’s disease (meaning they already had amyloid in the brain) those who were more physically active had less buildup of tau. And because they accumulated less tau over time, these more active individuals also experienced slower decline.The good news is that even low activity was associated with meaningfully slower decline. Benefits increased at moderate activity levels and then plateaued at the highest activity level.It may be helpful for Canadian physicians to incorporate counselling on physical activity into dementia-prevention conversations, she said, noting that the challenge is often getting patients to engage in regular physical activity. “Many patients feel discouraged by broad goals like ‘exercise more’ or ‘aim for 10,000 steps’. A more helpful strategy is to encourage them to start very small. Even a five minute walk once a day can help establish a routine. Once that habit is in place, increasing activity over time becomes much easier. The key is consistency, not intensity,” she said.A similar study was recently published by Korean researchers in the Journal of Prevention of Alzheimer’s Disease. This study investigated the relationship between walking intensity and duration, to longitudinal changes in AD-related brain pathologies. The researchers looked at Aβ and tau accumulation, as well as neurodegeneration, and white matter hyperintensity (WMH).Data were used from the Korean Brain Aging Study for the Early Diagnosis and Prediction of AD (KBASE). This is a longitudinal cohort study which began in 2014 with the goal of developing new biomarkers for the early detection of AD. It included MRI and PET scans at baseline and at four-year follow-up.A total of 151 older adults were included. Analyses showed that over four-years, long-duration or high-intensity walking was associated with significantly reduced Aβ accumulation compared to low or no-waking groups. But no associations were found with tau, neurodegeneration or WMH volume, the study said. For patients, the Alzheimer Society of Canada website offers resources to help encourage exercise in patients.

Daily steps appear to slow down cognitive decline in those with Alzheimer risk

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