Working Paper: NBER ID: w20599
Authors: Nils Wernerfelt; David Slusky; Richard Zeckhauser
Abstract: One in twelve Americans suffers from asthma and its annual costs are estimated to exceed $50 billion. Simultaneously, the root causes of the disease remain unknown. A recent hypothesis speculates that maternal vitamin D levels during pregnancy affect the probability the fetus later develops asthma. In two large-scale studies, we test this hypothesis using a natural experiment afforded by historical variation in sunlight, a major source of vitamin D. Specifically, holding the birth location and month fixed, we see how exogenous within-location variation in sunlight across birth years affects the probability of asthma onset. We show that this measurement of sunlight correlates with actual exposure, and consistent with pre-existing results from the fetal development literature, we find substantial and highly significant evidence in both datasets that increased sunlight during the second trimester lowers the subsequent probability of asthma. Our results suggest policies designed to augment vitamin D levels in pregnant women, the large majority of whom are vitamin D insufficient, could be very cost-effective.
Keywords: asthma; vitamin D; sunlight; pregnancy; public health
JEL Codes: I12; I18; J13
Edges that are evidenced by causal inference methods are in orange, and the rest are in light blue.
| Cause | Effect |
|---|---|
| Sunlight exposure during the second trimester (J22) | Probability of asthma diagnosis later in life (C41) |
| Sunlight exposure during the second trimester (J22) | Rate of asthma emergencies (I11) |
| Sunlight exposure during the second trimester (J22) | Maternal vitamin D levels (I15) |
| Maternal vitamin D levels (I15) | Probability of asthma diagnosis later in life (C41) |
| Maternal vitamin D levels (I15) | Rate of asthma emergencies (I11) |