Is Muscular Strength a Predictor of Atrial Fibrillation in Older Adults?

Atrial fibrillation (AFib) is the most common type of irregular heartbeat that is seen in clinical settings, and affects approximately 1% of the U.S. population.

Risk factors for the development of AFib include older age, obesity, hypertension, diabetes, heart valve disease, excessive alcohol intake, obstructive sleep apnea, and chronic inflammation. It has also become apparent in recent years that a low level of physical activity is a risk factor for AFib.

Some individuals with AFib will be asymptomatic (no symptoms), while others will experience light-headedness, fatigue, heart palpitations, fatigue, and/or shortness of breath. If left untreated, AFib significantly increases the risk of stroke. In fact, it is estimated that one in six strokes are due to AFib. This translates to approximately 132,000 strokes per year in the U.S. due to AFib! It is important to note that many individuals with AFib do not have it constantly; their heart rhythm is actually normal some (or much) of the time. In other individuals, AFib is persistently present.

Since muscular strength is an important component of physical fitness, let’s take a closer look at strength and AFib. One recent study sought to examine the relationship between muscular strength and future risk of developing AFib. A total of 827 healthy Finnish adults with an average age of 69 years underwent a measurement of handgrip strength at baseline. None of the participants had any history of AFib. Using a device called a handgrip dynamometer, the average of two measurements from the dominant hand was used as the handgrip strength score, which was then expressed relative to body weight. Participants were then carefully followed for an average of 15.7 years, during which time 265 AFib cases were documented.

Researchers then divided participants into three categories of baseline strength (low, moderate, and high) based on age and sex. The Figure below illustrates the risk of developing AFib across the three strength categories. Using the low strength group as the referent, those with moderate and high strength at baseline were 25% and 39% less likely to develop AFib during the follow-up period, respectively. It is important to note that the researchers took several factors into account when performing their analyses; these included age and sex, smoking status, resting blood pressure, resting heart rate, blood cholesterol levels, alcohol intake, and physical activity.

The authors concluded that higher levels of muscular strength are associated with a decreased future risk of AFib in a generally healthy population of older adults. Since the most recent Physical Activity Guidelines for Americans recommend at least 2 days of strength training per week, meeting these Guidelines is likely to increase muscular strength among individuals with lower levels of strength and to maintain strength in those with higher levels of strength. Along with controlling the modifiable risk factors mentioned at the beginning of the blog, performing strength training on a regular basis may be an important part of the overall strategy for preventing AFib.  

Reference
Kunutsor, S., et al. (2020). Handgrip strength and risk of atrial fibrillation. Am J Cardiol. Published ahead of print.

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