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A daily total of 3,800 to 9,800 steps was tied to lower dementia risk, longitudinal data from the U.K. Biobank showed.

The optimal dose of daily steps -- the value with the highest dementia risk reduction -- was 9,826 steps (HR 0.49, 95% CI 0.39-0.62), according to Borja del Pozo Cruz, PhD, of the University of Southern Denmark in Odense, and colleagues.

The minimal step dose -- the point at which dementia risk was half of the maximum reduction -- was 3,826 steps per day (HR 0.75, 95% CI 0.67-0.83), the researchers reported in .

Step intensity mattered. The optimal cadence dose for the highest 30 minutes of the day was 112 steps per minute (HR 0.38, 95% CI 0.24-0.60).

"The optimal dose was estimated at 9,800 steps per day, just under the popular target of 10,000 steps," del Pozo Cruz and co-authors noted. "We found no minimal threshold for the beneficial association of step counts with incident dementia."

"We estimated the minimum dose at approximately 3,800 steps per day, which was associated with 25% lower incident dementia," the researchers added. "Other studies have found 4,400 steps to be associated with mortality outcomes. This finding suggests that population-wide dementia prevention might be improved by shifting away from the least-active end of the step-count distributions."

The researchers address an "important, yet unexamined, link between daily step count and incident dementia," noted Elizabeth Planalp, PhD, and Ozioma Okonkwo, PhD, both of the University of Wisconsin in Madison, in an accompanying the report.

But a key finding "del Pozo Cruz and colleagues surprisingly did not discuss in detail was that higher step intensity -- a 'mere' 112 steps/min in a 30-minute epoch -- had the greatest impact on reducing dementia incidence in this cohort (62% vs 50% risk reduction for 9,800 daily steps), and that this observation was made in analyses that also adjusted for total steps," Planalp and Okonkwo pointed out.

"While 112 steps/min is a rather brisk cadence, '112' is conceivably a much more tractable and less intimidating number for most individuals than '10,000,' especially if they have been physically inactive or underactive," the editorialists observed.

The study assessed daily step count from wrist-worn accelerometers for 78,430 people 40 to 79 years old in the cohort from February 2013 to December 2015. Researchers evaluated total number of daily steps, whether steps were incidental (less than 40 steps per minute) or purposeful (40 or more steps per minute), and peak 30-minute cadence (average steps/minute for the 30 highest minutes of the day, which were not necessarily consecutive).

Participants had an average age of 61; about 55% were female and 97% were white. Over a mean follow-up of 6.9 years, 866 people developed dementia. Incident dementia was determined by hospitalization or primary care records, or was listed as an underlying or contributory cause of death in registry data.

For incidental steps, the optimal dose was 3,677 steps (HR 0.58, 95% CI 0.44-0.72). For purposeful steps, the optimal dose was 6,315 steps (HR 0.43, 95% CI 0.32-0.58).

"This study represents an important contribution to step count-based recommendations for dementia prevention," del Pozo Cruz and co-authors wrote. "Step count-based recommendations have the advantage of being easy to communicate, interpret, and measure, and may be particularly relevant for people who accumulate their physical activity in an unstructured manner."

"For such individuals, it may be otherwise challenging to track physical activity or determine whether they are sufficiently active relative to current minute- and intensity-based physical activity guidelines (i.e., 150 to 300 minutes per week of moderate to vigorous physical activity)," they noted.

Limitations include the study's observational design, which precludes causal inferences. In addition, reverse causation or unmeasured confounding may have influenced results.

"The age range of participants may have resulted in limited dementia cases, meaning our results may not be generalizable to older populations," the researchers acknowledged.

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