Birth order and multiple sclerosis

No significant difference in birth order and risk of multiple sclerosis (MS) was found in a large‐scale investigation employing 2 different study methods: case‐control and comparison of birth order with expected distribution. This finding is at variance with conflicting results of 2 recently published investigations. Our findings suggest that birth order cannot be used as a surrogate for age‐of‐infection, but must be measured directly in further studying the role of delayed childhood infection in the pathopoiesis of MS.