Late nights and disease

15Staying up late makes for a swell time, but not in a good way.

A finding appearing in the Sept. 15 Biological Psychiatry offers more evidence that lack of sleep can lead to inflammation and disease.

After one night of too little sleep, women volunteers in a study by researchers at the University of California, Los Angeles had higher levels of a chemical that triggers inflammation than after a full night of sleep.

Previous research with animals has shown that staying up all night can trigger stress reactions, including elevating some markers of inflammation. Inflammation can lead to disease. But people usually experience milder sleep deprivation, missing out on a few hours of sleep each night.

The increase in markers of inflammation after mild sleep deprivation shows how stressful even this more common sleep loss is, comments Amita Sehgal, a neuroscientist and Howard Hughes Medical Institute investigator at the University of Pennsylvania.

“The fact that this happens in a scenario that more commonly is experienced by people indicates that this is more of a health concern than previously thought,” Sehgal says.

Michael Irwin of UCLA and his colleagues tested levels of a protein called NF-kappaB in the blood of 14 healthy volunteers, seven men and seven women. The protein is a key regulator of inflammation and its activity has been linked to diabetes, heart disease and cancer.

All of the volunteers normally slept from, on average, 10:30 p.m. until 7:30 a.m. The researchers drew blood from the volunteers in the morning after a normal night of sleep, after a night in which the volunteers stayed awake until 3:00 a.m., and again after a night of recovery sleep.

One late night was all it took to cause a spike of the inflammation-promoting protein in women, the researchers found. The levels dropped to normal again after the night of recovery sleep.

Men in the study didn’t show any difference in the levels of NF-kappaB in their blood after missing some shut-eye. But Irwin cautions against making too much of the gender differences until larger studies can confirm the results.

“The study was never designed to test sex differences,” Irwin says. Women do have a greater risk of developing sleep disorders and inflammatory disorders as they age, but men also suffer from inflammation-linked illnesses.

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rwin and his colleagues plan to test whether men have higher levels of inflammatory chemicals after several nights of sleep loss. It’s also possible that, in the men, the inflammation-causing chemicals spiked during the night, and then the level dropped before the researchers measured it in the morning, Irwin says.

“The findings really stress the importance of a good night’s sleep,” says Irwin. “We tend to prioritize our daytime activities, but this is one more example of how important sleep is to maintaining health.”