Reduced Childhood Outdoor Exposure Raises Pediatric Multiple Sclerosis (PedMS) Risk

Sun exposure may influence MS susceptibility, but evidence in pediatric-onset MS (PedMS) is limited. We examined whether reduced early-childhood outdoor time (a proxy for lower sun exposure) is associated with PedMS risk.

In the Italian multicenter PEDIGREE Study, environmental data were collected using the PEQ-IT questionnaire. We enrolled individuals < 18 years with PedMS and disease duration ≤ 5 years and controls without CNS inflammatory disorders. Outdoor time was reported by season and age (0-1, 1-2, 3-5 years); reduced activity was defined as < 60 min/week.

We included 114 PedMS cases and 121 controls. Cases were 77.2% female; mean (SD) age 16.8 (2.7) years; mean (SD) age at onset 14.2 (2.6) years; median EDSS 1.0 (range 0-4.0). Associations were strongest in winter: reduced outdoor time was associated with higher odds of PedMS in the first year (adjOR 3.02, 95%CI 1.50-6.08), ages 1-2 (adjOR 2.72, 95%CI 1.45-5.09), and ages 3-5 (adjOR 2.66, 95%CI 1.40-5.07). Across ages 0-5, low winter outdoor activity remained strongly associated (adjOR 4.30, 95%CI 1.82-10.17). Other seasons showed weaker but overall significant trends.

Limited early-childhood outdoor activity may be associated with increased PedMS risk; larger longitudinal studies are needed.