Daily Step Counts, Step Intensity, And Mortality Risk Among U.s. Adults

Global physical activity guidelines committees have called for prospective studies on stepping and health outcomes to inform future recommendations. While step counts have been inversely associated with mortality, the role of stepping intensity is less clear. Most existing studies lack racial and ethnic diversity in their study populations. PURPOSE: To investigate associations between step counts, stepping intensity, and mortality risk in a diverse sample of U.S. adults. METHODS: Prospective analysis of adults (aged 40+) in the U.S. from the National Health and Nutrition Examination Survey (NHANES), which included an oversampling of racial and ethnic minority groups. Participants wore wrist-based accelerometers for up to 9 days (2011-14). We used machine learning models (“stepcount”) to derive stepping metrics. All-cause mortality was ascertained through December 2018. Cox proportional hazards regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI), adjusted for age, gender, race/ethnicity, body mass index, education, alcohol use, smoking status, frailty, self-rated health, mobility, and a history of health conditions. RESULTS: Among 5,300 individuals (weighted N = 192,396,305; mean age = 60 years, [standard deviation (SD) = 12]; 2,777 [52%] women), the mean daily step count was 8,257 [4,893]. Over a mean follow-up of 6.7 years [1.6], there were 695 deaths. A 1,000-step increase in daily steps was associated with an 11% lower risk of mortality (HR = 0.90, 95%CI:0.88-0.93). Inverse associations were observed for a 1,000-step increase among men (HR = 0.92, 95%CI: 0.89-0.96), women (HR = 0.88, 95%CI: 0.84-0.93), non-Hispanic Whites (HR = 0.90, 95%CI: 0.86-0.95), non-Hispanic Blacks (HR = 0.89, 95%CI: 0.84-0.95), and Hispanics (HR = 0.90, 95%CI: 0.83-0.98). There was no association between peak 30-minute cadence and mortality risk after adjusting for step count or for mean cadence of bouts lasting at least two minutes and mortality. CONCLUSION: Higher daily step counts were associated with lower all-cause mortality among U.S. men, women, and racial and ethnic subgroups. These findings suggest that physical activity recommendations that promote overall step volume, rather than intensity or sustained bouts, may be an effective strategy for lowering mortality risk. Supported by: AS, CM, JF, GH, and DWH are supported by the NIH Intramural Research Program. AD is funded by the Wellcome Trust (223100/Z/21/Z), Novo Nordisk, Swiss Re, and the British Heart Foundation Centre of Research Excellence (RE/18/3/34214). AD received consulting fees from the University of Wisconsin and Harvard University (both NIH R01 grants) and a donation from SwissRe for China Kadoorie Biobank data collection. SC is funded by Novo Nordisk. AD and SC released analysis software under an academic license with potential commercial use.