Long working hours were associated with an increased risk of atrial fibrillation, the most common cardiac arrhythmia. Because atrial fibrillation has been a known risk factor for stroke, this could be one of the mechanisms that explain the previously observed increased risk of stroke among those working long hours. However, the study could not prove a ''cause-and-effect'' relationship; therefore, its results need to be interpreted with caution. Nevertheless, it adds evidence to the ongoing theme that lifestyle can play a role in promoting atrial fibrillation.
In the new study, Kivimaki et al. tracked outcomes for nearly 85,500 people in the United Kingdom, Denmark, Sweden and Finland. The investigators found that people who worked 55 or more hours a week were about 40% more likely to develop atrial fibrillation over 10 years than those who worked between 35 to 40 hours per week. For every 1,000 people in the study, an extra 5.2 cases of atrial fibrillation occurred among those working long hours during the 10 years of follow-up, the study found. The researchers noted that atrial fibrillation is known to contribute to the development of stroke, but also other adverse health outcomes, such as heart failure and stroke-related dementia.