Long working hours may increase risk of AF
People who worked long hours, with 55 working hours/week or more, have a higher risk of developing atrial fibrillation (AF) than those who worked standard hours (35–40 hours/week), according to a pooled analysis of data from the IPD-Work* Consortium.
After a mean follow-up of 10 years, individuals who worked long hours were more than 40 percent more likely to develop AF than those working standard hours after adjusting for sex, age, and socioeconomic status (hazard ratio [HR], 1.42; p=0.0031). [Eur Heart J 2017; doi:10.1093/eurheartj/ehx324]
The increased risk remained after taking into account of pre-existing coronary heart disease at AF diagnosis (HR, 1.41; p=0.0039), and persisted even after excluding individuals with cardiovascular disease at baseline or during follow-up (HR, 1.36; p=0.0180).
“Nine out of 10 incident AF cases occurred among those free of pre-existing or concurrent cardiovascular disease, suggesting that the observed excess risk of AF is likely to reflect the effect of long working hours rather than the effect of pre-existing or concurrent cardiovascular disease,” said the researchers.
Additional adjustment for potential confounders and lifestyle factors such as diabetes, respiratory disease, infection, depression and anxiety, antihypertensive medication, high blood pressure, total and HDL-cholesterol or physical activity, obesity, smoking, and alcohol consumption did not change the association (HR, 1.42; p=0.12).
Also, stratifying the analyses by number of working hours per week showed that the risk of developing AF increased with increasing hours spent at work (HR, 1.02 for 41–48 hours/week, 1.17 for 49–54 hours/week, and 1.42 for ≥55 hours/week), although only the association with the longest hour category was significant (≥55 hours/week; p=0.0031).
“In absolute terms, the increased risk of [AF] among individuals with long working hours is relatively modest. The number of cases varied between 13 and 449 in the included studies,” observed the researchers.
The prospective multicohort study included eight European observational cohorts with 85,494 participants (mean age 43.4 years, 35 percent men) without AF at baseline from Finland, Sweden, Denmark, and the United Kingdom. During a mean follow-up of 10 years, 1,061 incident cases of AF were recorded, which translates to a cumulative incidence of 12.4 per 1000. The cases were identified from electrocardiograms, hospital records, death certificates, or drug reimbursement registers, and a majority (71 percent) occurred before age 65.
AF ─ the most common cardiac arrhythmia ─ is a risk factor for stroke and heart failure, according to the researchers.
“The long follow-up is not necessarily a strength but rather a limitation of the analyses, given that … all analyses used baseline measures of working hours and adjustment variables,” noted Drs Bakhtawar Mahmoodi and Lucas Boersma from St Antonius Hospital in Nieuwegein, the Netherlands, in an editorial. “[P]eople may have changed their job and working hours during the follow-up, the baseline adjustment variables are also subject to change during follow-up.” [Eur Heart J 2017;doi:10.1093/eurheartj/ehx385]
“Although the results of the present study apparently identify an association between working hours and AF, whether the relationship is causal or not remains to be determined,” they added.