Protective environmental factors for Neuromyelitis Optica

A study was recently published that discussed potential early-life environmental risk factors for NMO. MS has been shown to be associated with several environmental factors, but less is known about environmental factors and NMO. Graves et al looked at environmental questionnaire data for children with NMO (36), MS (491) and clinically isolated syndrome (CIS) who had high risk of MS. All individuals in the study had disease onset before age of 18. Graves et al also enrolled 224 healthy controls who had no history of autoimmune disease. Questionnaires included information about pregnancy exposure and complications, how the child was delivered (cesarean versus vaginal), and early childhood exposures (breastfeeding, length of breastfeeding, exposure to cigarette smoke, daycare attendance etc.).

NMO children were younger at onset than those with MS/CIS and were more likely to be African American. Most (58%) children diagnosed with NMO were AQP4-IgG positive, and those that were positive were more likely to be female and non-white than those who were AQP4-IgG negative. Exposure to daycare and breastfeeding were associated with lower odds of having NMO versus being a healthy control. Cesarean section delivery was associated with higher odds of NMO versus being a healthy control. Also, children of mothers who had a college-level education or higher had lower odds of having NMO versus children of mothers who did not complete high school. Father’s education, insurance type, and exposure to cigarette smoking, exposure to Epstein Barr Virus were not significantly associated with NMO.

Graves et al. theorized that breastfeeding is protective against NMO because of mother to child transmission of antigens and immune cells that lead to improved immunity for the child. They also theorized that daycare attendance is protective because children get exposed to many different pathogens in daycare, leading to increased immunity. Based on the results of this study, the authors believe that NMO and MS have different risk factors and are indeed different diseases. They also noted that the sample size of NMO patients in this study was small, so more studies with larger samples of NMO patients should be conducted.

Original research: Graves J, Grandhe S, Weinfurtner K et al. Protective environmental factors for neuromyelitis optica. Neurology. 2014 Nov;83: 1929-1929.