With Alzheimer’s accounting for 60–70 per cent of dementia cases worldwide, and that there is no cure for Alzheimer’s disease, it becomes crucial to understand what this study’s findings can mean for everyday preventive strategies, how simple lifestyle changes like walking may influence brain health, and what experts recommend to reduce risk, support cognitive function, and potentially slow the progression of the disease.

Knowing Alzheimer’s

Dementia prevalence in India is estimated at 7.4 per cent among adults over the age of 60, which translates to approximately 88 lakh people currently living with dementia.

Alzheimer’s disease, the most common cause of dementia, represents the majority of these cases. Globally, according to the World Health Organization (WHO), around 5.7 crore people were affected by dementia in 2021, with over 60 per cent residing in low-income and middle-income countries. Nearly 1 crore new cases are diagnosed annually, underscoring the growing global burden of the disease.

The Mayo Clinic defines Alzheimer’s disease as a “biological process that begins with the appearance of a buildup of proteins in the form of amyloid plaques and neurofibrillary tangles in the brain. This causes brain cells to die over time and the brain to shrink.”

Early symptoms of Alzheimer’s include forgetting recent events or conversations, misplacing items, or experiencing difficulties with planning and problem-solving. As the disease progresses, it leads to serious memory loss and affects a person’s ability to perform everyday tasks. In advanced stages, the loss of brain function can cause complications such as dehydration, poor nutrition, and infections, which may ultimately result in death. While there is currently no cure for Alzheimer’s, medications can improve symptoms or slow cognitive decline. Supportive programs and services for patients and caregivers also play a critical role in maintaining quality of life.

Given the absence of a definitive cure, the focus on preventive strategies, lifestyle modifications, and early interventions is paramount. Walking, as demonstrated by the new study, could serve as a practical and scientifically backed approach to reducing Alzheimer’s risk and slowing the onset of symptoms.

What the study found

The study conducted by researchers at Mass General Brigham analysed data from nearly 300 adults aged 50 to 90 who were part of the Harvard Ageing Brain Study. All participants were cognitively healthy at the start of the study and were followed for up to 14 years. The researchers used brain scans to monitor two key Alzheimer’s proteins—amyloid-beta and tau—while tracking participants’ daily steps through pedometers.

The results were striking. Individuals who walked 3,000–5,000 steps per day experienced a delay of three years in cognitive decline. Those who increased their daily steps to 5,000–7,500 saw an impressive seven-year delay in cognitive deterioration. Participants with lower activity levels experienced faster accumulation of tau proteins and quicker declines in memory and thinking skills.

“This sheds light on why some people who appear to be on an Alzheimer’s disease trajectory don’t decline as quickly as others,” said Dr Jasmeer Chhatwal, senior author of the study. The findings indicate that lifestyle factors such as walking influence the earliest stages of Alzheimer’s, suggesting that interventions at this stage may slow the emergence of cognitive symptoms.

Walking appears to impact the brain on a cellular level. The proteins amyloid-beta and tau are naturally present in everyone’s brain, but in Alzheimer’s disease, they clump together, disrupting normal neural functions. The study revealed that participants who were more physically active had slower tau protein buildup, which is closely associated with memory loss. Essentially, walking seemed to “cleanse” the brain, keeping neurons healthier and more resilient against the disease.

Dr Reisa Sperling, a neurologist and co-principal investigator of the Harvard Ageing Brain Study, explained that “these findings show us that it’s possible to build cognitive resilience and resistance to tau pathology in the setting of preclinical Alzheimer’s disease. This is particularly encouraging for our quest to ultimately prevent Alzheimer’s disease dementia.”

However, the researchers acknowledged several limitations. They noted, “This is an observational study and we are unable to fully rule out the potential influence of reverse causality. Future randomised clinical trials are required to establish causal relationships.” While pedometer-based measurements were a strength, they only captured baseline activity and did not account for intensity, duration, history, or other forms of exercise such as swimming or resistance training. The HABS cohort, consisting mainly of highly educated, non-Hispanic white individuals and excluding those with certain vascular conditions, “may limit the generalizability of our findings to other populations.”

Experts weigh in

Commenting on the study, Dr Vinit Suri, Senior Consultant Neurologist at Indraprastha Apollo Hospitals, New Delhi, cautioned that while the findings are encouraging, this was a small observational study. “This is not a large-scale randomised controlled trial, and it is difficult to infer that exercise or walking alone can delay Alzheimer’s onset. More large-scale studies are required to establish causality,” Dr Suri noted. Still, the benefits for memory function are clear.

He emphasised that physical exercise improves memory function, though whether it can delay dementia specifically remains unclear. “Regular physical exercise of at least 30 to 45 minutes, four to five times a week, is recommended,” he said. “Both physical and mental exercises will improve memory function.”

Dr Suri also highlighted the importance of adequate sleep. “Sleep has been shown to reduce the accumulation of tau and amyloid in the brain. The brain heals itself during sleep, which reduces the burden of tau and amyloid, the same substrates that are affected by exercise,” he explained. Combining physical activity with sufficient sleep, he added, can help improve memory and may contribute to reducing risk factors associated with Alzheimer’s.

He also shared a practical mnemonic he uses with patients to improve memory and overall cognitive health: M-E-D-S-S. “M stands for memory exercises, such as learning new skills, playing cards, or taking up a musical instrument. E is for physical exercise, which can include cardio, yoga, or walking. D is for diet, focusing on avoiding smoking, limiting alcohol, and including omega-3 and B12-rich foods, such as salmon, nuts, chia seeds, or soy. The first S is for sleep, ensuring adequate rest, and the second S is for stress management,” he explained.

He concluded by reiterating the main takeaway- while this study cannot prove that exercise delays Alzheimer’s, “we can clearly say that memory function improves with physical exercise, adequate sleep, and a healthy lifestyle. These are simple, scientifically supported strategies to support brain health, even if their effect on preventing Alzheimer’s requires further large-scale research.”