Does the season or month of birth influence disease progression in multiple sclerosis?

We investigated the influence of season and birth month on sustained progression to Expanded Disability Status Scale 6 (requires a cane) through a database review of 2,319 definite multiple sclerosis (MS) patients followed for a mean 19.3 years, until July 2003 in British Columbia, Canada. The season of birth had a marginal effect on disease progression (p = 0.051), with winter babies exhibiting the slowest progression (p = 0.048). Birth month had a significant effect on progression (p = 0.038), mainly due to those January born having a 40% (95% CI 32.9-47.4) chance of requiring a cane later than those born in other months. There was some evidence to suggest that the gestational period had a small but long-lasting effect on later disease progression in British Columbia, Canada. Copyright (c) 2006 S. Karger AG, Basel.