Chronic work stress causes biological changes that increase the risk of heart disease, say the authors of a 12-year study of more than 10,000 British civil servants.

The study found that male and female workers younger than 50 who said they had stressful jobs were nearly 70 percent more likely to develop coronary heart disease (CHD) than stress-free colleagues, BBC News reported. The findings were published in the European Heart Journal.

"Among people of retirement age -- and therefore less likely to be exposed to work stress -- the effect on CHD was less strong," said lead researcher Dr. Tarani Chandola of University College London.

Chandola and colleagues said stress appears to disrupt the part of the nervous system that tells the heart how to work and controls heart-rate variability, BBC News reported.

The researchers also found that stressed-out workers were less likely to exercise or eat sufficient amounts of fresh fruits and vegetables. Both are lifestyle factors believed to play a role in the prevention of heart disease.

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