A child in my clinic had a small appendage in front of her ear, called a preauricular tag. I told the mother that I had just returned from a conference where I learned these are more common at high altitude. She replied, “But his father has one also.”
“Yes,” I explained, “There is an interaction between the genes and low oxygen.”
Birth defects can be increased or decreased by the chronic hypoxia at high altitude. Geneticist Igor Salvatierra from the Hospital Materno-infantil discussed the interaction between oxygen levels and chromosomes at the Chronic Hypoxia conference in La Paz, Bolivia. He focused on a deformity we also see more commonly in Summit County, Colorado at 2800 meters: outer ear deformities – microtia. Birth defects can be structural, like the outer ear, or functional, such as deafness, and occur in 1 out of 33 infants worldwide. Only 50% of abnormalities can be linked to a specific cause. Club foot is an example of a birth defect that is less common at higher elevations. In contrast, microtia is three times more common, with preauricular tags twice as common as at sea level. This is due to the interaction between genes and the environment.
Research has identified an enzyme called Jarid1B that is affected by hypoxia, including sleep apnea, copy number variation (CNV) and epigenetic factors such as stress and diet. These act on chromosome 1q32.1 to change the coding of proteins involved in the development of ear cartilage very early in fetal development.
At lower altitudes, the hypoxic environment can be caused by sleep apnea. In early pregnancy this could be one of many factors that, if added to the genetic predispostion, could cause a deformity in the fetus. Luckily the fetus is fully formed before the sleep difficulties in late pregnancy.
Should pregnant mothers or women who are hoping to conceive sleep on oxygen?
From what I learned in La Paz, not necessarily. There are factors in our low-oxygen environment that decrease our risk of other diseases.