In this startup, tech culture, business has shifted and this means young and older people are working longer and hard hours in the office. We’ve talked about the effect staring at the computer has on your eyes short-term but how does working long hours in the office affect the rest of your body.

A new study suggests how this can harm your heart. As noted, researchers found people who put in 55 hours or more a week have an increased risk of developing atrial fibrillation - which is an irregular heart rhythm linked to stroke compared to those who work 40 hours or less.

Published in the journal European Heart out of the University of London, combined data from 8 previous studies that analyzed more than 85,000 women and men. None of these subjects had atrial fibrillation at the study’s start but over time 1,061 had developed it over the course of 10 years.

In other words, those who worked the most were 40% more likely to developing AFib, compared to those who worked 35 to 40 hours a week—even after the results were adjusted for factors such as age, gender, obesity, socioeconomic status, smoking status, risky alcohol use, and leisure-time physical activity.

90% of these cases occurred in people who didn’t have any heart-related disease suggesting time at work in excess without any pre-existing conditions was responsible for the condition developing.

The authors point out that a 40% increased risk of AFib may not be a big deal, depending on how high a person’s overall risk for heart disease already is. For someone who already has several risk factors (like being older, male, diabetic, or a smoker, for example), any added risk could be important.

They also say their finding could help explain, at least partially, why people who work long hours have been shown to have an increased risk of stroke. ( AFib is known to contribute to the development of stroke, as well as heart failure, stroke-related dementia, and other serious health problems.)

Physically demanding work could also contribute to an increased risk of AFib and other heart problems, but the editorial writers point out that manual labor jobs are often well regulated so workers don't put in more than 55 hours a week.