Genetics account for many traits we share with our family. Those dimples, green eyes and the ability to roll your tongue? All genetics. Daytime sleepiness and the love of hot sauce? Environmental. But what about sleep apnea? Recently, a team of researchers from Hungary sought to answer just that with a sleep apnea study on twins. What they found may surprise you.
The study, which was recently published in the journal Respiratory Research, found that while conditions such as daytime sleepiness in the general population appear to be purely environmental, sleep apnea is heritable.
Dr. Kelley Mingus treats sleep apnea in his Bend, Oregon, practice. He clarifies exactly what these findings mean.
"When they say daytime sleepiness is environmental, they mean that it is influenced by some outside factor in the patient’s environment, not genetics," Mingus says. "Maybe the subject is tired because he or she was up late the night before or didn’t get a good night’s sleep due to a snoring spouse."
Heritability is defined as a statistic used to measure a degree of variation in a population due to genetics. In the study, heritability was measured in 71 pairs of twins, because twin studies account for both environment and heritability.
The researchers gave each of the twins a test called the Epworth Sleepiness Scale, or ESS, questionnaire, as well as recording their blood pressure, heart rate and full medical history. Subjects of the study were then monitored via an overnight polysomnography test, which measured their oxygen, sleep stages, movement and electroencephalography readings, among other things.
The researchers used this data to calculate things like the patients' oxygen desaturation index, respiratory disturbance index and apnea-hypopnea index and found that 41 percent of the participants had sleep apnea, with varying degrees of severity. Of those cases of sleep apnea, nearly three-quarters appeared to be heritable - in other words, due to genetics.
"Researchers believe sleep apnea can be heritable due to similarities in the shape of the oropharynx and size of the tongue," says Mingus, who also points out that daytime sleepiness that is not due to sleep apnea could be due to another serious condition. "One factor for daytime sleepiness the study did not mention was insomnia, which often goes hand in hand with sleep apnea and can be just as serious even if it occurs on its own."
Mingus recommends if you are having trouble falling asleep at night or find yourself feeling tired and sluggish throughout the day, seek the help of a sleep specialist. Furthermore, if someone in your biological family suffers from sleep apnea, consider getting screened for the condition yourself.