Nicholas Koemel and colleagues at the University of Sydney analyzed data from 22,618 UK Biobank participants, most in their early 60s, who wore wrist accelerometers for seven days between 2013 and 2015. The researchers tracked these participants for roughly eight years, recording dementia diagnoses through November 2022.
During follow-up, 170 participants developed dementia. Among those who engaged in no vigorous activity, 2.5 percent were diagnosed with dementia. Those who performed sporadic vigorous lifestyle activities like rushing for the bus or carrying heavy shopping, but did not exercise deliberately, saw dementia rates drop to 0.71 percent. People who combined deliberate exercise with daily vigorous activities had the lowest rate at 0.59 percent.
An accumulation of just 3.7 minutes per day of vigorous routine movement was linked to a 48 percent lower dementia risk. Koemel's team also found that such activity correlated with larger volumes of grey matter in several brain regions and reduced white matter hyperintensities, areas of abnormal brain tissue.
The study is observational and cannot prove causation. Mike Trott at the University of Queensland noted that the activity measurement covered only one week years before dementia diagnoses occurred. Reverse causation is also possible, Koemel explained, since undiagnosed dementia could have reduced some participants' ability to engage in vigorous activity.
The researchers theorize that vigorous bursts may improve vascular health by lowering blood pressure and reducing arterial stiffness, potentially preventing vascular brain injury. Energetic activity also requires fast posture adjustments, engaging the brain's cerebellar and sensorimotor networks and potentially contributing to larger grey matter volumes in these areas.
Koemel cautioned that people should gradually increase physical activity rather than make radical shifts, which could raise injury risk.