Vigorous intermittent lifestyle physical activity (VILPA) and mortality risk among US adults: a wearables-based national cohort study

Vigorous intermittent lifestyle physical activity (VILPA) completed through normal daily living may offer a time-efficient avenue to accrue physical activity in a behaviourally sustainable manner. However, no research to date has explored its association with mortality in a nationally representative population. This study aimed to examine the dose-response association between VILPA and mortality risk in a nationally representative sample of US adults. This study included a nationally representative sample of 3,293 US adults from the 2011-14 National Health and Nutrition Examination Survey (NHANES) who self-reported no participation in structured exercise (52.3% female; mean age: 50.7 [SD: 16.6 years]. The dose-response relationship between VILPA and all-cause mortality was estimated using multivariable-adjusted cubic splines. Average daily frequency (bouts/day) and duration (minutes/day) of VILPA bouts lasting up to one minute were measured using a wrist-worn accelerometer. Over the mean (SD) 6.7 (1.4) year follow-up period, 290 all-cause mortality events occurred. Compared to the referent point (0 bouts per day), there was an L-shaped dose-response association where the median frequency (5.3 bouts per day) was associated with a 44% lower risk of all-cause mortality (HR: 0.56; 95% CI: 0.39, 0.82). The dose response curve was less steep beyond approximately 8 bouts per day (HR: 0.46; 95% CI: 0.28, 0.77). Findings for the median frequency of VILPA bouts (5.3 bouts per day) remained consistent after excluding participants with poor health (HR: 0.51: 95% CI: 0.29, 0.87) and those who completed no VILPA (HR: 0.57: 95% CI: 0.38, 0.86). When excluding adults with prevalent cardiovascular disease or cancer at baseline (n = 2,731, 152 events), the dose-response relationship was similar, although the 95% CIs crossed unity for most of the curve (e.g. median frequency of VILPA bouts HR: 0.68: 95% CI: 0.41, 1.11). In a nationally representative sample of US adults, short bursts of intermittent vigorous physical activity were associated with a lower risk of mortality. Excluding those with prevalent cardiovascular disease and cancer led to attenuated dose-response curves and wider confidence intervals, suggesting that the observed relationships may, at least partly, be driven by existing disease-induced reverse causation. While these results highlight some potential of VILPA as a time-efficient source of activity, additional observational studies with longer follow up and larger sample sizes are warranted.