Atrial fibrillation (AF) is the most common cardiac arrhythmia.

There has been research into whether physical activity can help lower AF risk, but many studies use research-grade accelerometers. While these have provided useful insights, they are often only used for a short amount of time, e.g., between 4-7 days. With more people now using wearable devices, researchers can study physical activity patterns over much longer periods and in larger, real-world populations.

This edition of Tap into Research looks at a study that investigated whether daily step counts were linked to AF risk using Apple Watches.

How were smartwatches used in the study?

Participants in this study were from the Framingham Heart Study, which began in 1948 and now includes up to 3 generations of families. In 2016, participants who owned an iPhone were offered an Apple Watch to take part in additional monitoring.

Participants were encouraged to wear their Apple Watch daily, which measured their heart rate and step count. Researchers also extracted watch wear time.

Researchers then linked this data to each participant’s CHARGE-AF score: a validated tool to estimate the risk of someone developing AF in the next 5 years.

What did the study find?

The study included 923 participants.

Participants wore their watch for more than 5 hours for a median of 324 days (IQR 137-563). The median daily wear time was 13.6 hours (IQR 12.4-14.7), and the median daily step count was 7,227 (IQR 5,699-8,970).

A higher number of steps was associated with a lower predicted risk of AF. After adjusting for age, sex, and wear time, every 1,000 steps was associated with a 0.08% lower CHARGE-AF risk score.

This relationship between step count and risk of AF was different for men and women, and for participants with and without obesity:

• Higher step counts were linked to a bigger reduction in predicted AF risk for men than women (0.14% lower CHARGE-AF score per 1,000 steps in men, compared with 0.05% lower CHARGE-AF score per 1,000 steps for women).
• Higher step counts were linked to a bigger reduction in predicted AF risk for participants with obesity than those without (0.10% lower CHARGE-AF score per 1,000 steps, while those without obesity had a 0.03% lower CHARGE-AF score per 1,000 steps).

Why does this matter?

Understanding how step count relates to AF risk matters because increasing daily step count could be a simple, practical way to lower risk. Future studies could explore this relationship in more diverse groups, including a wider range of ages and ethnic groups, to check whether the patterns found in this study are similar in other populations.

Read the paper: Step Count, Self-reported Physical Activity, and Predicted 5-Year Risk of Atrial Fibrillation: Cross-sectional Analysis (jmir.org)

Related