Physical Fitness Correlates with a Lower Risk of Atrial Fibrillation and Stroke
As one might expect, people who better maintain physical fitness into later life exhibit lesser degrees of age-related disease. In this case, the correlation is specifically for forms of cardiovascular disease, but researchers have reported that numerous other improvements in health can be linked to greater fitness. Animal studies can and do show causation in this relationship between fitness and age-related disease. It is reasonable to believe that the human correlations also largely reflect a causal relationship. There are a great many good reasons to make the effort to better maintain physical fitness throughout life.
A new study assessed 15,450 individuals without atrial fibrillation who were referred for a treadmill test between 2003 and 2012. The average age was 55 years and 59% were men. Fitness was assessed using the Bruce protocol, where participants are asked to walk faster and at a steeper grade in successive three-minute stages. Fitness was calculated according to the rate of energy expenditure the participants achieved, which was expressed in metabolic equivalents (METs).
Participants were followed for new-onset atrial fibrillation, stroke, myocardial infarction, and death. The researchers analysed the associations between fitness and atrial fibrillation, stroke, and major adverse cardiovascular events (MACE; a composite of stroke, myocardial infarction and death) after adjusting for factors that could influence the relationships including age, sex, cholesterol level, kidney function, prior stroke, hypertension, and medications.
During a median of 137 months, 515 participants (3.3%) developed atrial fibrillation. Each one MET increase on the treadmill test was associated with an 8% lower risk of atrial fibrillation, 12% lower risk of stroke and 14% lower risk of MACE. Participants were divided into three fitness levels according to METs achieved during the treadmill test: low (less than 8.57 METs), medium (8.57 to 10.72) and high (more than 10.72). The probability of remaining free from atrial fibrillation over a five-year period was 97.1%, 98.4%, and 98.4% in the low, medium and high fitness groups, respectively.