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Higher step count significantly associated with lower mortality in older women
A recent study found that a step count of 4,400 steps per day was associated with significantly lower mortality among older women compared with 2,700 steps per day. Mortality decreased steadily and leveled off after approximately 7,500 steps per day.
“A common goal of 10,000 steps per day has been perpetuated by the lay press and is often used as the default by software programs on wearables and smartphones.” I-Min Lee, MBBS, ScD, of the division of preventive medicine at Brigham and Women’s Hospital at Harvard Medical School and the department of epidemiology at Harvard T.H. Chan School of Public Health, and colleagues wrote. “However, the origin of the goal of 10,000 steps per day is unclear.”
Researchers conducted a prospective cohort study with participants from the Women’s Health Study. Participants wore accelerometers at the hip for 7 consecutive days and were instructed to only remove the device while sleeping and during water-based activities. Data from women who wore the device for a minimum of 10 hours per day for at least 4 days were included in the study results. Researchers reviewed the number of steps per day and several measurements of step intensity.
Participants were divided into four quartiles based on mean steps taken per day. Individuals with the lowest step counts were in the first quartile and those with the highest step counts were in the fourth quartile.
After review, 16,741 women with a mean age of 72 years were included in the study, including 504 who died during follow up. The mean step count of the study population was 5,499 per day. Among participants, 51.4% of time was spent at 0 steps per minute, 45.5% of time was spent at 1 to 39 steps per minute, and 3.1% of time was spent at 40 steps or more per minute.
In the first quartile, participants took a median of 2,718 steps per day and had an HR associated with mortality of 1 (reference) after adjusting for potential confounders. The median step count of the second quartile was 4,363 steps per day and the adjusted HR was 0.59 (95% CI, 0.47-0.75). The third quartile had a median step count of 5,905 steps per day and an adjusted HR of 0.54 (95% CI, 0.41-0.72). The median step count of the fourth quartile was 8,442 steps per day and the adjusted HR was 0.42 (95% CI, 0.3-0.6).
Researchers initially found that higher step intensities were associated with significantly lower mortality rates, but most were no longer significant after adjusting for steps per day.
“Number of steps, rather than stepping intensity, was the step metric consistently related to lower mortality rates,” Lee and colleagues wrote. “These findings may serve as encouragement to the many sedentary individuals for whom 10,000 steps per day pose an unattainable goal.”– by Erin Michael
Disclosures: Lee reports receiving grants from the National Institutes of Health during the conduct of the study. Please see study for all other authors’ relevant financial disclosures.