Spending time indoors during childhood ups risk of developing multiple sclerosis
Low levels of sun exposure throughout childhood appears to be associated with an increased risk of developing multiple sclerosis (MS) in adulthood, a study reports. Notably, the risk is greatest in those who spend most time indoors and use sun protection frequently in their limited time outdoors.
The study included 2,251 MS patients and 4,028 non-MS controls enrolled in the Environmental Risk Factors in MS (EnvIMS) study. The participants provided data on their sun exposure behaviours for 5-year age intervals from birth, with the study focusing on the first three age intervals (≤15 years).
Researchers compared two conceptual life course epidemiology models that can be used to explain disease aetiology: the critical period and accumulation models. The critical period model suggests the existence of a time period during which an individual is susceptible to exposures that determine disease risk, whereas the accumulation model suggests that longer duration of exposure time heightens the risk of disease in individuals irrespective of when exposure occurs.
Based on the results, the accumulation model emerged as the best model, which demonstrated that the lowest vs highest sun exposure at all three age intervals yielded a nearly 50-percent increased risk of MS (risk ratio [RR], 1.47; 95 percent CI, 1.24–1.74).
On latent class analysis, the highest risk of MS was observed in the group of individuals with low sun exposure during both summer and winter and high sun protection use than in the group with high sun exposure and low sun protection use (RR, 1.76; 1.27–2.46).
The findings underscore the importance of promoting balanced safe sun exposure practices tailored to specific populations in order to reduce disease burden, especially in countries and cultures where children spend a lot of time indoors, researchers said.