Walking as few as 4400 steps per day may decrease the risk for all-cause mortality among older women, according to a study published online today in JAMA Internal Medicine and presented simultaneously at the American College of Sports Medicine (ACSM) 2019 Annual Meeting.
The risk for death fell with increasing number of steps per day, and these benefits leveled off after 7500 steps/day.
The study is the first to evaluate the association between step intensity and long-term health outcomes, and it found the intensity of walking did not seem to have an impact on mortality.
"These findings may serve as encouragement to the many sedentary individuals for whom 10,000 steps/day pose an unattainable goal," write author I-Min Lee, MBBS, ScD, from Harvard Medical School in Boston, Massachusetts, and colleagues.
Widespread belief holds that 10,000 steps/day improves health. Many software programs for devices that measure steps, such as smartphone apps, use 10,000 steps as a default goal. Yet not much research supports that number.
"The present study provides a unique contribution because there are few data on the association between steps and mortality," the authors write.
The US Health and Human Services 2018 physical activity guidelines for Americans use minutes rather than steps and recommend 150 min/week of moderate intensity physical activity, including brisk walking.
Yet the idea of counting steps may translate more easily into clinical practice, particularly because many devices already measure steps.
To get a better idea of the association between steps/day and health benefits, researchers analyzed data from a subgroup of women who participated in the Women's Health Study, a randomized trial that evaluated the effect of low-dose aspirin and vitamin E on cardiovascular disease and cancer prevention in women ages 45 years and older.
When the larger trial ended, researchers invited women to participate in an observational cohort study, which took place from 2011 to 2015. Participants wore ActiGraph accelerometers to objectively measure steps taken during their waking hours throughout a 7-day period.
The analysis included 16,741 women whose "steps data" could be successfully downloaded, and who were compliant with wearing the accelerometer. Included women had a mean age of 72 years, and a mean step count of 5499 steps/day. Researchers followed women for a mean of 4.3 years, during which time 504 women died.
After adjustment for age, ActiGraph wear time, smoking status, alcohol use, general health, and 10 factors related to risk for cancer or CVD, the risk for all-cause mortality significantly decreased with increasing number of steps per day (P for trend, < .01).
Compared with women who took the fewest steps per day (median 2718), women who took 4363 steps per day had 41% decreased risk for all-cause mortality (hazard ratio [HR], 0.59; 95% confidence interval [CI], 0.47 - 0.75. This risk dropped by 46% among women who took 5905 steps/day (HR, 0.54; 95% CI, 0.41 - 0.72), and by 58% for women who took the most steps/day (median 8442; HR, 0.42; 95% CI, 0.30 - 0.60).
The risk for all-cause mortality progressively fell by 15% for each additional 1000 steps/day. However, this benefit leveled off at about 7500 steps/day.
Analyses of step intensity adjusted for steps per day suggested step intensity had little effect on mortality (P for trend, .03), suggesting the number of steps walked — rather than intensity of walking — may be more important to affect risk for death in older women.
The authors mentioned several study limitations. Participants in the larger women's health study were primarily white and had a high socioeconomic status. Women in this substudy may have been more active than women in the larger US population. For these reasons, the results may not apply to a more diverse population, less active women, or men.
The study was supported by a grant from the National Institutes of Health. One or more authors report grants, personal fees, travel fees, advisory board membership from one or more of the following: the National Institutes of Health, ActiGraph, and/or the National Cancer Institute.
American College of Sports Medicine (ACSM) 2019 Annual Meeting. Presented May 29, 2019.
JAMA Intern Med. Published online May 29, 2019. Full text
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