New research published in the journal Cancer Epidemiology, Biomarkers and Prevention has found a link between high sun exposure during pregnancy and decreased risk of their children developing childhood cancer.
Given vitamin D’s effect on the immune system and its potential anticancer properties, it has been theorized that vitamin D and good amounts of sun exposure may be protective against childhood cancer. While there have been many epidemiologic studies that have shown that vitamin D and sun exposure reduce the risk of internal cancers for adult populations, only one such study has looked at the relationship in children. The researchers in the present study, led by Christina Lombardi, wanted to shore up this lack of data.
The researchers looked for children aged 0 to 5 in the California Cancer Registry from 1988 to 2007. They then matched these children with children who were born in California and were cancer free the first 5 years of life. For every one child in the California Cancer Registry, the researchers matched them with 20 cancer-free controls. In all, this came out to 10,476 cancer cases and 207,568 cancer-free controls comprising their study.
The researchers then estimated how much UVR these children’s mothers got during pregnancy by using a model called ANUSPLIN. This model estimates how much UVR areas get based on ground-level measurements, latitude, longitude and elevation and puts this UVR into units of Watt-hours/m². By looking at the birth places on the birth certificates, the researchers were then able to split the children’s mothers into quartiles ranging from those who received the least amount of UVR to those who received the most during pregnancy.
They then examined the risk of getting various cancers during childhood based on how much UVR mothers got. Here’s what they found:
- Acute lymphoblastic leukemia was the most common type of cancer (31%), followed by central nervous system tumors (21%), and followed by neuroblastoma (11%).
- In mothers who got the most UVR, their children had a decreased risk of getting acute lymphoblastic leukemia (OR: 0.89, 95% CI: 0.81–0.99), hepatoblastoma (OR: 0.69, 95% CI: 0.48–1.00), and non-Hodgkin’s lymphoma (OR: 0.71, 95% CI: 0.50–1.02) when compared to mothers who got the least amount of UVR.
- When analyzed by race, there was a 16% decrease in odds in children getting acute lymphoblastic leukemia among Hispanic mothers and a 35% decrease in odds among Black mothers living in counties in the highest quartile of UVR exposure.
- For non-Hodgkin’s lymphoma, there was a 39% decrease in odds for children with White mothers in the highest UVR quartile compared to lowest (OR: 0.61, 95% CI: 0.37–1.01). No effect was observed for children of Hispanic or Black mothers.
The researchers concluded,
“Our results suggest a possible protective association between UVR and acute lymphoblastic leukemia, hepatoblastoma, and non-Hodgkin’s lymphoma in children diagnosed with any of these cancers through age 5.”
They suggested the finding may be due to either vitamin D or other UVR mediated pathways, unless there is some kind of confounding factor.
The study does have some limitations. First, the study measured UVR using a model that composites several years of data, thus the researchers were unable to narrow in on specific trimester exposure. This study offers poor insight if UVR and vitamin D are more important in certain trimesters for protection against childhood cancers. Furthermore, this study was unable to account for if women moved during pregnancy or if they went on vacation, potentially diluting their data to a certain extent.
In conclusion, it appears that sun exposure shows a protective association against some childhood cancers. Whether it’s from vitamin D or sun exposure or some other factor is not currently known.