Working nights can be tough, in large measure because human beings were meant to be alert during the day. Fighting the body's natural clock leads to health problems, researchers say, and may lead to shorter lifespans.
For many workers, however, working the wee hours of the morning gives them the flexibility to better balance other demands they have throughout the day.
But a new study by researchers at the Karolinska Institute in Stockholm warns that those under age 20 are at increased risk of developing multiple sclerosis (MS) because of disruption to their circadian rhythms and sleep patterns caused by shift work.
For the purposes of the study, shift work was defined as either permanent or alternating hours of work from 9 p.m. to 7 a.m.
"Our analysis revealed a significant association between working shift at a young age and occurrence of MS," says lead researcher Anna Hedstroem in a statement releasing the findings. "Given the association was observed in two independent studies strongly supports a true relationship between shift work and disease risk."
Results from the study, published in Annals of Neurology, showed that those diagnosed with MS had at least a twofold greater risk of developing the disease than those who never worked night shifts.
The study involved nearly 14,000 Swedish residents between 16 and 70 years of age.
"With shift work, your biological clock gets out of whack and you have poorer sleep quality, Hedstroem told AFP. "Both these things have been shown to impact the immune system."
The institute notes that previous research has determined that shift work, which includes working rotating shifts in addition to overnight work, increases the risk of cardiovascular disease, thyroid disorders and cancer.
Disrupting the body's circadian rhythm and reducing hours of sleep are believed to disturb the secretion of melatonin, a hormone that regulates wake and sleep cycles, and increase the body's response to infections, leading to disease.
Authors of the study cautioned, however, that more study is needed to determine the exact causes of increased incidence of MS among those who have participated in shift work.
Stories from CNNMoney