Temporal Changes in a Novel Metric of Physical Activity Tracking (Personal Activity Intelligence) and Mortality: The HUNT Study, Norway

Abstract

BackgroundPersonal Activity Intelligence (PAI) is a novel activity metric that translates heart rate variations during exercise into a weekly score. Weekly PAI scores assessed at a single point in time were found to associate with lower risk of premature cardiovascular disease (CVD) mortality in the general healthy population. However, to date, the associations between long-term longitudinal changes in weekly PAI scores and mortality have not been explored. PurposeThe aim of the present study was to prospectively examine the association between change in weekly PAI scores estimated 10 years apart, and risk of mortality from CVD and all-causes. MethodsWe performed a prospective cohort study of 11,870 men and 13,010 women without known CVD in Norway. By using data from the Nord-Trøndelag Health Study (HUNT), PAI was estimated twice, ten years apart (HUNT1 1984-86 and HUNT2 1995-97). Mortality was followed-up until December 31, 2015. Adjusted hazard ratios (AHR) and 95% confidence intervals (CI) for death from CVD and all-causes related to temporal changes in PAI were estimated using Cox regression analyses. ResultsDuring a mean (SD) of 18 (4) years of follow-up, there were 4782 deaths, including 1560 deaths caused by CVD. Multi-adjusted analyses demonstrated that participants achieving a score of ≥100 PAI at both time points had 32% lower risk of CVD mortality (AHR 0.68; CI: 0.54–0.86) for CVD mortality and 20% lower risk of all-cause mortality (AHR 0.80; CI: 71–0.91) compared with participants obtaining <100 weekly PAI at both measurements. For participants having <100 PAI in HUNT1 but ≥100 PAI in HUNT2, the AHRs were 0.87 (CI: 0.74–1.03) for CVD mortality, and 0.86 (CI: 0.79–0.95) for all-cause mortality. We also found an inverse linear relationship between change in PAI and risk of CVD mortality among participants with 0 PAI (P < 0.01), and ≤50 PAI (P = 0.04) in HUNT1, indicating that an increase in PAI over time is associated with lower risk of mortality. Excluding the first three years of follow-up did not substantially alter the findings. Increasing PAI score from <100 PAI in HUNT1 to ≥100 PAI in HUNT2 was associated with 6.6 years gained lifespan. ConclusionAmong men and women without known CVD, an increase in PAI score and sustained high PAI score over a 10-year period was associated with lower risk of mortality.