Poor sleep can speed cancer growth and increase tumor aggressiveness, according to a new study led by an Israeli researcher.

The tumors could grow in a shorter amount of time compared to cancer in patients who get a good night's sleep, the research shows.

The study was conducted by the University of Chicago and the University of Louisville in the United States, led by Dr. Fahed Hakim, a pediatric specialist in lungs and sleep from the Rambam Medical Center in Haifa, the largest city in northern Israel.

Hakim and his colleagues studied two different sets of rats. One group was allowed an uninterrupted night's sleep while the others were disrupted various times during the night for one week.

"After a week of these sleeping patterns, we injected both groups with cancer cells and observed their growth over a period of four weeks," Dr. Hakim told Xinhua.

"We continued with the same sleep configuration during the four weeks and we observed afterwards that those mice in the sleep-deprived group had grown tumors twice as big as the other group," he said.

The tumors grew not only bigger in the sleep-deprived group but also much more malignant, as they penetrated much deeper into the tissue and at a much faster rate than cancer in those rodents that had a normal sleep, according to the research.

"We found that disrupted sleep affects the immune system and the cells called macrophage, which have to fight the cancer, actually begin helping it grow," the researcher said.

The study was published in December's issue of Cancer Research journal and was originally begun two years ago as a research into sleep apnea, a condition in which the airway in the throat is blocked by soft tissue during sleep. The patients frequently choke during their sleep and wake up continuously.

"We began researching this condition, but this applies also to modern life as there can be multiple reasons for waking up continuously during the night, like a noisy neighborhood, or the cell phones ringing constantly," Dr. Hakim said.

"There is a huge percentage of the population that is not getting a clean sleep everyday, something that affects our health directly," he added.

To combat sleep fragmentation, the researcher recommended turning off all phones and external lights, as well as sports before going to bed.

"Or a good book, something to make you sleep tight, but mostly avoiding any kind of noise," said the researcher, "but really, it's something to be worried about if it happens many times during the night and many nights per week."