A growing number of studies provide evidence of the human body's need to get sufficient rest, particularly at night, after a hard day's work.
A new study suggests that lack of sleep does not just make you feel lousy and unfocused. It also has effects that can be life-threatening. In the study published in the journal Cancer Research, researchers revealed that poor quality of sleep characterized by frequent waking can enhance the growth and aggression of tumors.
Researchers of the study experimented with two groups of mice. The mice in the first group were allowed to sleep peacefully during the day (mice are nocturnal animals so they sleep during the day) while the mice in the second group had motorized brush sweeping through their cages every two minutes which causes them to wake up and go back to sleep.
The setup went on for seven days after which, the mice were injected with tumor cells. The researchers observed that while all the mice developed tumors within nine to 12 days, the mice whose sleep was disturbed had tumors that were twice as big as the tumors found on mice with undisturbed sleep.
The researchers also found that in mice implanted with tumor cells in the thigh muscles, those with disrupted sleep developed aggressive tumors that invaded surrounding tissues.
"It's not the tumor, it's the immune system," said study researcher David Gozal, chairman of pediatrics at the University of Chicago Comer Children's Hospital. "Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive."
Sleep apparently has an effect on the immune system. The researchers found that the mice with fragmented sleep had more M2-type tumor-associated macrophages (TAMs), which stop immune response and promote tumor growth. The well-rested mice, on the other hand, had more of the M1-TAMs, known to promote strong immune response and fight cancer cells.
"This study offers biological plausibility to the epidemiological associations between perturbed sleep and cancer outcomes," Gozal said. "The take home message is to take care of your sleep quality and quantity like you take care of your bank account."