Longer bouts of exercise may be associated with decreased mortality and cardiovascular disease

1. In this prospective cohort study, cumulative all-cause mortality and risk for cardiovascular disease were lower among adults who accumulated most of their steps in longer bouts of exercise, independently of step count.

2. Stronger associations between bout length and outcomes were seen among sedentary individuals with fewer than 5000 daily steps.

Evidence Rating Level: 2 (Good)

Study Rundown: A large portion of daily steps come from routine activities that involve only short, sporadic bouts of light- to moderate-intensity movement. The accumulation of steps from these routine activities is particularly relevant for individuals with suboptimal activity levels, who may not be able to easily engage in longer-duration exercise. However, it is unknown whether steps taken during longer exercise sessions may be more beneficial for health. This study aimed to determine whether the pattern of daily step accumulation in adults is associated with risk for all-cause mortality and cardiovascular disease (CVD) independent of the total number of steps taken. At nearly ten years of follow-up, the cumulative all-cause mortality and risk for CVD were lower among individuals who accumulated most of their steps in longer bouts. These associations were more profound among sedentary individuals who accumulated fewer than 5000 steps a day. Subgroup analyses excluding participants with a high frailty index or who considered their health fair or poor showed similar results. Results were also not significantly affected by adjustment for biomarkers, total caloric intake, or self-reported walking pace. The generalizability of this study is limited by its observational design with potential residual confounding and reverse causation; one-time measurement of activity; and a short window for accelerometer data collection. Nevertheless, this study suggests that longer exercise sessions are inversely correlated with mortality and CVD risk, especially among adults with lower daily step counts.

Click to read this study in AIM

Relevant Reading: Revisiting the concept of bout: associations of moderate-to-vigorous physical activity sessions and non-sessions with mortality

In-Depth [prospective cohort]: This study aimed to determine whether the length of bouts at which most daily steps are accumulated may be associated with risk of mortality and CVD. Participants were obtained from the UK Biobank; exercise data were recorded using an accelerometer between June 1, 2013, and December 23, 2015, while follow-up took place until November 30, 2022. Participants were included if they had accelerometer data from at least 3 valid days and took fewer than 8000 steps on average per day. Sedentary participants were defined as accumulating <5000 steps per day, while low-active participants accumulated 5000 to 7999 steps per day. The outcomes were all-cause mortality and CVD incidence. The sample included 33,560 participants (mean age, 62.0 years) who were followed up for 7.9 years on average (266,283 person-years). A total of 735 participants died, and 3119 CVD events were recorded. The median daily step count was 5165 steps, and 42.9% of participants accumulated most of their daily steps in bouts under 5 minutes, while 33.5% accumulated most of their steps in 5- to 10-minute bouts, 15.5% in 10- to 15-minute bouts, and 8.0% in 15-minute bouts or longer. At 9.5 years, the cumulative all-cause mortality risk was 4.36% (95% confidence interval [CI], 3.52% to 5.19%) among participants who accumulated most of their steps in bouts shorter than 5 minutes, 1.83% (95% CI, 1.29% to 2.36%) for 5- to 10-minute bouts, 0.84% (95% CI, 0.13% to 1.53%) for 10- to 15-minute bouts, and 0.80% (95% CI, 0.00% to 1.89%) for 15-minute bouts or longer. Compared with bouts shorter than 5 minutes, the relative risks (RRs) were 0.42 (95% CI, 0.35 to 0.50) for 5- to 10-minute bouts, 0.19 (95% CI, 0.14 to 0.27) for 10- to 15-minute bouts, and 0.17 (95% CI, 0.11 to 0.28) for 15-minute bouts or longer. Cumulative risk for CVD was 13.03% (95% CI, 11.92% to 14.14%) for bouts shorter than 5 minutes, compared with 11.09% (95% CI, 9.88% to 12.29%) for 5- to 10-minute bouts, 7.71% (95% CI, 5.67% to 9.70%) for 10- to 15-minute bouts, and 4.39% (95% CI, 1.89% to 6.83%) for bouts of 15 minutes or longer. Relative to bouts shorter than 5 minutes, the RRs were 0.85 (95% CI, 0.79 to 0.91) for 5- to 10-minute bouts, 0.58 (95% CI, 0.52 to 0.65) for 10- to 15-minute bouts, and 0.32 (95% CI, 0.25 to 0.40) for 15-minute bouts or longer. Stratified analyses showed stronger associations among sedentary participants; in the group with 15-minute bouts or longer, corresponding to a relative risk of 0.15 (95% CI, 0.06 to 0.38) compared with under-5-minute bouts and a risk difference of -3.38 percentage points (95% CI, -5.62 to -1.14 percentage points). Additional analyses that excluded participants with a high frailty index and self-rated fair or poor health showed similar results, as did adjustment for biomarkers, total caloric intake, and self-reported walking pace. Overall, this study suggests that longer bouts of exercise were associated with decreased mortality and CVD risk independent of daily step count.

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