Does the choice of stepping intensity metric influence dose-response associations with mortality? A UK population cohort study of 70,174 adults

BackgroundResearch on the health effects of stepping intensity in free-living environments is limited and inconclusive. Inconsistent use of stepping intensity estimation metrics could explain current equivocal results. We aimed to examine and compare a range of different cadence-based metrics in terms of their multivariable-adjusted associations with all-cause (ACM) cardiovascular disease (CVD), cancer and physical-activity (PA)-related cancer mortality. MethodsThis prospective cohort study included participants with valid wrist-worn accelerometer data from the UK Biobank. We estimated stepping intensity using ten different cadence-based metrics, including eight peak-cadence metrics (defined as averaged steps / min of the highest but not necessarily consecutive minutes) that most of whom have appeared in prior literature, plus two non-peak-cadence metrics: 1) average daily cadence, defined as steps/accelerometer wearing mins, and 2) average cadence of purposeful steps, defined as averaged steps / min of minutes with [≥]40 steps. We rescaled each metric into a standardised cadence scale with mean of 0 and standard deviation (SD) of 1, using (absolute-mean)/SD. We compared the dose-response associations of each stepping intensity estimation metrics with mortality outcomes using previously published modelling involving Cox-restricted-cubic-spline model, presented as overlay plots on standardised and absolute cadence scales. ResultsAmong 70,336 participants (age [SD], 61.6 [7.8] years; female, 40,933 [58%]) followed up for a median of 8.0 years, all cadence-based metrics, besides the average cadence of purposeful steps, exhibited a comparable beneficial dose-response association with ACM/CVD/cancer mortality, with 95% CI largely overlapped (e.g., at -0.2 standardised steps/min, the hazard ratio (HR) of ACM for peak 1- and peak 30-min cadence were: 0.72, 95%CI [0.65, 0.82] and 0.66 [0.60, 0.73], respectively). The average cadence of purposeful steps only did not show dose-response associations with mortality outcomes (e.g., the HR that corresponds to the standardised median for the average cadence of purposeful steps in ACM was 0.98 [95% CI: 0.86, 1.12]. ConclusionBesides the average cadence of purposeful steps, all stepping intensity estimation metrics demonstrated comparable beneficial dose-response associations with mortality of all-cause, CVD and cancer, suggesting these cadence-based metrics may be used interchangeably for estimating associations of free-living stepping intensity with health outcomes and applied in different research scenarios accordingly.