An important goal for future Physical Activity Guidelines for Americans will be to develop a recommendation for the number of steps individuals should achieve each day to promote health.1 One of the first steps in developing a recommendation is to observe the number of steps taken per day that is associated with the lowest mortality risk. The new study by Paluch et al2 examined the association between step count and mortality in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort of middle-aged adults, with a balanced sample of Black and White individuals followed-up for a mean of 10.8 years. Paluch et al2 observed that walking at least 7000 steps each day was associated with 60% to 70% reduction in mortality risk compared with walking less. The results demonstrated by Paluch et al2 were similar to those recently published from the National Health and Nutrition Examination Survey (NHANES)3 and many other previous studies4 that have suggested that there is a threshold for mortality risk reduction at approximately 10 000 steps/d. In contrast, in a cohort of older aged women participating in the Women’s Health Study, the risk reduction leveled off at approximately 7500 steps/d,4 but age-specific analysis in NHANES did not show a similar tapering in association at step counts higher than 7500 steps/d.3
When translating these results to the public, it is important to note that most of these studies have measured steps using a single type of research-grade accelerometer, the Actigraph, which is not a device used by the public. It is unclear the extent to which steps measured on these activity monitors compare with steps measured by common consumer devices, including smartwatches, pedometers, and smartphone applications. Many comparison studies have been conducted in laboratory settings among young healthy adults, but these do not necessarily reflect real-life wear experiences that will be generalizable to the population as a whole.5 In the next few years, the number of articles published relating step counts to mortality will accelerate rapidly as many other large cohort studies have completed accelerometry measurement using a wide variety of research-grade accelerometer devices with 10 years of follow-up or more. It will be critical for simultaneous investigations to be conducted at a large scale, comparing step counting among research-grade and consumer devices in the free-living setting and among populations with diverse stride lengths and gait patterns (varying by factors such as age, height, weight, and mobility status), of which there are limited studies published to date.5,6
The reason for conducting comparison studies is not to develop distinct guidelines for different devices or subgroups of the population, but rather to understand the variability so that we can develop one clear message that is most appropriate to the public. Some devices may have bias in terms of step measurement at different activity intensity6 and may not record steps as accurately in older adults or individuals with obesity or mobility disorders. For example, when adults who were obese wore an Actigraph monitor in a laboratory setting, the device only recorded 80% of steps walked at a moderate pace, while other devices recorded close to 100% of steps walked.6 If we in the public health community are to move toward using these devices more for physical activity prescription, these details will need to be explored in more depth.
The next critical task for developing an appropriate national recommendation for step achievement will be to conduct studies with more sociodemographic diversity and to focus on more diverse health outcomes. Mortality is not the only matter of concern when it comes to developing a guideline for health promotion, and we also need to expand our study beyond cardiovascular and metabolic diseases. It is critical to focus our investigations on other health outcomes, such as quality of life, years of healthy life, mobility, mental health, and dementia and Alzheimer disease. Unfortunately, to date, few of the large physical activity or lifestyle intervention studies that have measured such outcomes have also measured steps achievement7; therefore, we will likely have to rely mostly on observational analyses for the first national step guideline. I hope to encourage investigators and research funders to focus on these understudied topics that will provide evidence to support a national step guideline.
Published: September 3, 2021. doi:10.1001/jamanetworkopen.2021.25267
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Spartano NL. JAMA Network Open.
Corresponding Author: Nicole L. Spartano, PhD, Section of Endocrinology, Diabetes, Nutrition and Weight Management, Boston University School of Medicine, 720 Harrison Ave, Doctors Office Bldg, Ste 8100, Boston, MA 02118 (firstname.lastname@example.org).
Conflict of Interest Disclosures: Dr Spartano reported receiving grants from the American Heart Association, Alzheimer’s Association, National Institutes of Health, and Novo Nordisk outside the submitted work.
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Spartano NL. What Are the Next Steps for Developing a National Steps Guideline? JAMA Netw Open. 2021;4(9):e2125267. doi:10.1001/jamanetworkopen.2021.25267
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