A long-term study of 11,000 British civil servants found a link between high job strain and coronary heart disease. While it doesn’t necessarily show a cause and effect between working long hours and getting heart disease, the study found that symptoms of heart disease were higher in those working long hours, Reuters reported.

An extra one or two hours of work beyond a seven-hour work day didn’t seem to increase risk of heart disease—but the risk was 60% higher for those who worked three to four hours overtime, according to the news report.

The study adjusted for other risk factors, such as smoking, being overweight, or having high cholesterol. However, the lifestyle of people working long hours could deteriorate over time, noted researcher Dr. Marianna Virtanen, an epidemiologist at the Finnish Institute of Occupational health and University College London, according to Reuters. For instance, working long hours could lead you to drink more or have a poor diet.

Furthermore, long hours might be associated with work-related stress or working while you are sick. “Overtime-induced work stress might contribute to a substantial proportion of cardiovascular disease,” Gordon McInnes, professor of clinical pharmacology at the University of Glasgow’s Western Infirmary, told Reuters.

The study findings are published in the European Heart Journal.