SNORING, like all other sounds, is caused by vibrations that cause particles in the air to form sound waves. For example, when we speak, our vocal cords vibrate to form our voice. When our stomach growls (borboygymus), our stomach and intestines vibrate as air and food move through them.
While we sleep, turbulent airflow can cause the tissues of the nose and throat to vibrate and give rise to snoring. But snoring is not necessarily a good thing, and it falls in the field of dentistry, and ear, nose and throat disorders.
The Journal of the American College of Chest Physicians has reported that snoring in women is a sign of pregnancy-induced high blood pressure, and a risk for growth retardation of the unborn child.
Hypertension (high blood pressure) disorders during pregnancy are a leading cause of maternal death in the United States and Great Britain, and are important causes of neonatal morbidity and mortality. The cause of these disorders is unknown.
Because snoring is common in pregnancy, investigators in Sweden studied more than 500 pregnant women to see what effect snoring had on their health, but according to Karl Franklin, MD, and colleagues at the Umea University Hospital in Sweden, no one has investigated whether snoring is associated with hypersensitive disorders of pregnancy.
Snoring can be a sign of increased upper airway resistance and obstructive sleep apnea (temporary pause in breathing), and is known to be associated with arterial hypertension and coronary artery disease.
Investigators looked into the snoring-related occurrence of pre-emclampsia, a toxemia of pregnancy characterized by hypertension, proteinuria (excessive serum proteins), and edema (a buildup of fluids in body tissues), as well as daytime sleepiness, and infant outcome. The study included a questionnaire that women completed on the day of their delivery, with the involvement of their husband or partner. It also included analyzing Apagar scores that reflected the infant’s heart rate, respiratory effect, muscle tone, reflex irritability, and colour, all measured shortly after birth.
Snoring increased during pregnancy. By the third trimester, 24 per cent of the women reported that they had begun snoring or increased their level of snoring. Twenty-three per cent said that their snoring had become habitual during the last week before delivery. Habitual snoring was described as snoring every night, or almost every night. Sleep apnea was observed in 11 per cent of habitual snorers compared with two (2) per cent of the nonfrequent snorers.
The habitual snorers also had a more pronounced weight increase during pregnancy. Fourteen per cent of the women who snored habitually had pregnancy-induced hypertension as compared with six (6) per cent of the nonfrequent snorers. Ten per cent of the women who habitually snored met the definition of pre-eclampsia with hypertension and proteinuria compared with 4 percent of the nonfrequent snorers.
Daytime sleepiness increasingly grew among all women during pregnancy, and no marked differences were observed between the habitual snorers and nonfrequent snorers. Daytime sleepiness started earlier in pregnancy than did snoring. Edema (swelling) of the face, hands, legs or feet occurred in 52 per cent of the habitual snorers compared with 30 per cent for others.
Infants born to mothers who were habitual snorers more frequently had lower birth weight and lower Apgar scores, a finding researchers described as ‘novel’. More than seven per cent of mothers who were habitual snorers delivered an infant with growth retardation at birth compared with 2.6 per cent among non-habitual snorers.
After adjusting for weight, age, and smoking habits, snoring remained a significant predictor of growth retardation. In addition to snoring, smoking is also found to be an independent predictor of growth retardation. An Apgar score of less than seven was more common in infants born to habitual snorers, as compared with infants born to occasional or nonsnorers.
For example, 12.4 per cent of infants of habitual snorers who were given an Apgar test at one minute after delivery had scores of less than seven compared with 3.6 per cent of the infants of nonfrequent snorers who were given the Apgar test one minute after delivery. Statistically, the percentage differences were even greater when the test was administered five minutes after delivery, but less frequent for both habitual snorers and infrequent snorers.
All the subjects who snored habitually and had pre-eclampsia started to snore before any sign of hypertension or proteinuria was present, and the habitual snoring was related to sleep apneas, and this includes that nocturnal upper airway obstruction may contribute top the development of pregnancy-induced hypertension and pre-emclampsia.
The experiment concludes that it is possible that pregnant women are especially vulnerable to increases in upper airway resistance, as breathing may also be restricted by an increase in the abdominal pressure affecting the diaphragm.
Respiratory sleep studies, including the treatment of sleep apnea in women with pre-eclampsia, are desirable, and may answer the question of whether there is an etiologic link between increased upper airway resistance and pre-emclampsia.
Though dentists are in a position to identify and treat patients with obstructive sleep apnea, the above study may not have much impact on a typical daily practice, as many women avoid dental treatment during pregnancy, or do not comprehend the relationship between dental care and sleep apnea.