Association of Accelerometer-Measured Light-Intensity Physical Activity with Cardiovascular Diseases: A Large Cohort Study.

Background: Light-intensity physical activity (LPA) constitutes a substantial portion of daily activities; however, it is more challenging to record and measure accurately compared to moderate- to vigorous-intensity physical activity (MVPA). Consequently, the health benefits associated with LPA are frequently overlooked. Our study aimed to investigate the associations of LPA pattern including objectively measured LPA's duration, proportion, and timing with risk of incident cardiovascular diseases (CVDs). Methods: With the UK Biobank, 83,658 participants free of CVD with valid accelerometry data were included between 2013 and 2015. Data on physical activity (PA) were collected using the Axivity AX3 wrist-based triaxial accelerometer worn for 1 week. LPA duration was estimated using machine learning models based on bouts data from wrist-worn accelerometers. The LPA proportion was calculated by dividing the amount of LPA by the sum of LPA and MVPA. LPA timing was determined using hierarchical clustering analysis based on the average duration of LPA within each time window across the 24-h cycle. CVDs of interest including coronary heart disease (CHD), stroke, heart failure (HF), and atrial fibrillation (AF) were identified through the linkage to hospital admission records and death registers. Results: Over a median follow-up duration of 7.98 (interquartile range: 7.43 to 8.47) years, a total of 2,239 CVDs, including 1,014 CHDs, 352 strokes, 796 AFs, and 194 HFs, were recorded. An L-shaped relationship was found between LPA duration and the risk of HF. Compared to individuals in the lowest quartile, those in the second (hazard ratio [HR], 0.64; 95% confidence interval [CI]: 0.44, 0.93), third (HR, 0.56; 95% CI: 0.37, 0.84), and highest quartile (HR, 0.65; 95% CI: 0.43, 0.99) of daily LPA were associated with lower risks of HF. Higher LPA in the morning, midday, and evening was associated with a higher risk of HF, whereas higher LPA in the night showed an adverse impact on HF risk. These findings were not observed for CHD, stroke, and AF. Conclusions: Our findings highlighted that maintaining sufficient duration of LPA might be beneficial for HF as a compensatory PA strategy, but it is also essential to regulate the proportion and timing of LPA.