Fitness-tracker step counts may hint at later brain disease

For a year, more than 22,000 American adults wore fitness trackers that logged their steps. The ones who moved least turned out to be the most exposed later on: adults averaging fewer than 5,000 steps a day were diagnosed with dementia, Parkinson's disease or stroke at almost twice the rate of those averaging more than 12,000. The figures come from a study presented at the 151st Annual Meeting of the American Neurological Association.

The team, led by Dr. Meet Popatbhai Kachhadia, a neurology resident at Florida Atlantic University's Charles E. Schmidt College of Medicine in Boca Raton, Florida, followed 22,517 American adults aged 40 and older for five years. Their average daily steps were sorted into three groups by median activity: low (4,800 steps a day), moderate (around 8,300) and high (roughly 12,600). Diagnoses were read from electronic health records. The study is likely the first to use a year of wearable data from the National Institutes of Health (NIH) All of Us Research Program, which focuses on diversity, including people who have historically been left out of medical research.

Over about five years, 343 participants received a new diagnosis of dementia, Parkinson's disease, stroke or transient ischemic attack (TIA, sometimes called a ministroke). The rate climbed as activity fell: about 3.8 diagnoses per 1,000 people followed for one year in the least-active group, against 2.1 in the most active, or about 80% higher. The researchers found that a pattern sustained over a full year predicted who would develop disease better than a single tracker reading or a questionnaire.

The link runs through the body's everyday health. The least-active group had an average body mass index (BMI) of 32.1, against 26.5 in the most active, and higher rates of diabetes (5.6% against 2.0%), high blood pressure (13.4% against 9.2%) and depression (8.6% against 3.1%). Physical activity helps control weight, blood pressure and blood sugar, all linked to stroke and cognitive decline. Depression was the single strongest predictor of later neurological disease, although the researchers note it can itself be an early symptom of dementia and Parkinson's. The study measures association, not cause.

For people who already wear a tracker, and for the clinicians who could read its data, the practical gain is an earlier signal. Kachhadia says a low count held across twelve months should prompt a health check, not a verdict on the brain, and that the next step is to factor in activity type and intensity. Dr. Marc A. Swerdloff, co-author and clinical affiliate at Florida Atlantic University, points to a realistic goal: people averaging around 8,000 steps a day had meaningfully lower rates of neurological disease than the least-active group, in line with federal guidance of about 150 minutes of moderate activity a week. "Nobody needs to reach 12,000," he said. The researchers give no timeline for clinical use.