Association between Activity Quotient and cause-specific mortality - A prospective cohort study of 0.5 million participants in Asia.

Background: Regular physical activity (PA) is important for reducing the risk of chronic diseases and improving overall health. Activity Quotient (AQ) is a novel metric that translates heart rate during PA into a weekly score, providing an objective measure of an individual's PA. We prospectively examined the association of AQ with cancer and cardiovascular (CVD) mortality outcomes, the two major causes of death, in a Taiwanese population.

Methods: A cohort of 515,608 healthy adults (52 % women) enrolled in a standard medical screening program was followed for mortality outcomes. The weekly AQ score of each participant was estimated based on self-reported PA intensity and weekly duration, and placed into six categories (0, ≤50, 51-99,100-149, 150-199, or ≥ 200 AQ per week). We used multivariable Cox proportional hazard models adjusted for potential confounders to estimate the hazard ratios (HR) and 95 % confidence intervals (CI).

Results: Higher weekly AQ scores were associated with lower risks of CVD, cancer, and all-cause mortalities. Compared with inactive individuals, HRs (CI) for the association of AQ scores of ≤50, 50-99, 100-149, 150-199, and ≥ 200 were 0.93 (0.89-0.97), 0.91 (0.85-0.96), 0.84 (0.77-0.91), 0.84 (0.74-0.96), and 0.81 (0.73-0.90) with cancer mortality; and 0.88 (0.83-0.93), 0.86 (0.80-0.93), 0.81 (0.73-0.90), 0.71 (0.60-0.85), and 0.73 (0.64-0.84) with CVD mortality, respectively. Subgroup analyses showed that meeting 50 AQ a week was associated with lower risk of disease specific mortality risk across age groups and among individuals with known risk factors. Higher weekly AQ scores were also associated with longer life expectancy, with the highest gains observed among those achieving 150-199 weekly AQ.

Conclusion: Our findings show that AQ may be an objective tool for assessing and tracking PA and predicting mortality risks. Encouraging individuals to achieve ≥50 AQ a week could have substantial public health benefits, including lower mortality from major chronic diseases as well as prolonged health- and life expectancy.