(Entrepreneur) — Overwork went straight to Douglas Heddings’ back. The founder of Heddings Property Group in New York City, Heddings has suffered from chronic stress-related back pain for more than a decade. Even as he recuperated from spine surgery, the pace didn’t let up. His inbox filled at the rate of 50 e-mails per hour. The back problem “has a great deal to do with the fact that I feel I have to be on call 24/7,” Heddings says. “This is not good for my mental and physical well-being.” Researchers agree. Frequent long hours can increase stress and touch off a host of health hazards, including insomnia and high blood pressure. Poor decision-making starts to creep in. And unlike your laptop, your system doesn’t have an internal fan to cool it down. A 2006 study at the University of California, Irvine found that chronic workweeks of more than 51 hours can triple the risk of hypertension. And, after looking over the data from a British study of civil servants, Marianna Virtanen of the Finnish Institute of Occupational Health found that workdays of 11 or 12 hours increase the risk of coronary events by 56 percent. Stress is the culprit, triggering the release of hormones that help contribute to plaque build-up inside arteries. Long days were also linked to sleep problems and depression.