The 1.3 million people in the Netherland who work regularly at night have an increased risk of diabetes and heart disease, the Dutch health council said on Tuesday.

The council bases its claim on an analysis of various research projects into the impact of night shifts on health.

It found that people who work at night are up to twice as likely to suffer from sleeping problems and are more likely to develop type 2 diabetes and develop heart and artery disease. This is because of the impact of night work on the body’s own clock.

Night workers account for up to one fifth of all cases of type 2 diabetes and 23% of cases of heart and artery disease, when they only account for 15% of the population, the health council said.

However, despite earlier claims there is no clear risk of night workers being more likely to develop breast cancer, the council said.

While the impact of night work on other diseases has not been properly researched, the health council said it is recommending that the government take steps to limit night work as much as possible.