MS is a central nervous system autoimmune inflammatory disorder. Shift work – defined in the study as permanent or alternating working hours between 9 p.m. and 7 a.m. – disrupts the body’s sleep patterns and circadian rhythm, or biological clock. Previous research has linked shift work with the increased risk of cardiovascular disease, thyroid disorders and cancer.
This new research, led by Dr. Anna Karin Hedström from the Karolinska Institutet in Stockholm, Sweden, found a connection between an increased risk of MS in teens who engaged in shift work before the age of 20.
Hedström and colleagues analyzed data from two population-based studies – one with 1,343 incident cases of MS and 2,900 controls and another with 5,129 prevalent MS cases and 4,509 controls. The researchers compared the occurrence of MS among study subjects exposed to shift work at various ages against those who had never been exposed. All study subjects resided in Sweden and were between the ages of 16 and 70.
“Our analysis revealed a significant association between working shift at a young age and occurrence of MS,” said. Hedström. “Given the association was observed in two independent studies strongly supports a true relationship between shift work and disease risk.”
Results showed that those in the incident MS cohort who had worked off-hour shifts for 3 years or longer before age 20 had a two-fold risk of developing MS compared with those who never worked shifts. Similarly, subjects in the prevalent cohort who engaged in shift work as teens had slightly more than a two-fold risk of MS than subjects who never worked shifts.
The authors suggest that disruption of circadian rhythm and sleep loss may play a role in the development of MS. The exact mechanisms behind this increased risk remain unclear, however, and further study is needed.
The findings appear in Annals of Neurology, a journal published by Wiley-Blackwell on behalf of the American Neurological Association and Child Neurology Society.