Researchers have an explanation as to why multiple sclerosis symptoms are less intense during the fall and winter.
For patients and clinicians alike, it has long been a mystery why symptoms of multiple sclerosis (MS) seem to get better in the winter and worse in the summer. A group of researchers, led by Francisco J. Quintana, PhD, at the Ann Romney Center for Neurologic Diseases at Brigham and Women’s Hospital (BWH), and collaborators at the Center for Research on Neuroimmunological Diseases (CIEN) at the Raul Carrea Institute for Neurological Research (FLENI) in Argentina, have found an explanation that could lead to a deeper understanding of the disease and more targeted multiple sclerosis treatment options for patients.
By first examining possible environmental factors and then preclinical studies of MS, the research team found that melatonin – a hormone involved in regulating a person’s sleep-wake cycle – may influence MS disease activity. The researchers found that during the fall and winter, the group of 139 relapsing MS patients they studied experienced a significant improvement in symptoms (a phenomenon that has been observed in previous studies). The team then explored a variety of environmental factors that have been proposed as possibly linked to MS symptoms.
The factor that was consistently associated with severity of MS symptoms was melatonin. Melatonin levels are known to correlate with day length. During the longer days of the spring and summer, levels are lower. During the shorter days of the fall and winter, levels are higher.
By investigating the effects of melatonin on the immune response that leads to MS symptoms, the researchers found that melatonin affected two kinds of cells that are important in MS disease progression: pathogenic T cells that directly attack and destroy tissue and regulatory T cells that keep pathogenic T cells in check.
“We found that melatonin has a protective effect,” says Quintana. “It dampens the immune response and helps keep the pathogenic T cells at bay.”
The researchers caution that this work does not mean MS patients should start taking supplements of melatonin, but should discuss any questions or concerns with their physicians. Although melatonin is available over the counter, it has significant drawbacks, including causing unwanted drowsiness. The team reported its findings in the journal Cell.
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– Jessica F./Haley B.