The Importance of Children Spending Time Outdoors

In a recently published case-control study, sun exposure preceding the pediatric onset of multiple sclerosis (MS) was compared between 332 children (recently diagnosed) to 534 matched controls at 16 MS centers around the US. After multi-variate adjustment, a dose-dependent effect of sun exposure was associated with a reduced risk for MS; children getting 30-60 minutes per day in the preceding summer had a 52% lower risk when compared to children getting less than 30 minutes, and those outside for 1-2 hours had an 81% lower risk. Living in sunnier climates was also linked to a lower risk of developing MS.

This study is consistent with the association observed in adults. Ninety-four studies were included in a meta-analysis which found an increase in MS prevalence at higher latitudes, and a systematic review of 10 studies and nearly 152,000 participants with MS found not only was latitude a risk factor, but the month of birth was also a significant risk factor. For example, individuals born in May had an 11% greater risk for a diagnosis of MS, while those born in November had a 12% lower risk. These results strongly suggest that maternal sun exposure is an important factor for subsequent risk. While a causal link has not been established, it is widely suspected that vitamin D availability drives the association. In a recent systematic review and meta-analysis, higher gestational vitamin D levels were associated with a 37% risk reduction for a diagnosis of MS later in life.