Clinical profile of patients with sleep apnea
A typical profile of an OSAHS patient is that of a middle-aged man, between the ages of 40 and 65 years old, a habitual snorer (with a long history of snoring which commenced in childhood), overweight, hypertensive and complaining of excessive daytime sleepiness. Although the classical picture of an OSAHS patient is an obese male, it also presents in women, especially post-menopausal women. It can also present itself in younger males who may or may not be overweight. This is the case because the manifestation of OSAHS is a result of the interaction of several factors; anatomical, neurological and genetic make-up.
Obesity is a major risk factor for OSAHS, but it is also true that obesity is a reversible condition. A Body Mass Index (BMI) greater than 28 kg/m2 predisposes to Sleep Breathing Disorders (SBD) and excess weight is present in 60-90% of those diagnosed with OSAHS. The circumference of the waist, neck and any fatty deposits on the pharyngeal walls are considered when making the diagnosis. The circumference of the neck increases with local fatty deposits, decreasing the upper respiratory tract radius. Also the fatty abdominal deposits cause a reduction in lung volume. Many patients with a high Apnea/Hypopnea Index (AHI) improve after achieving a substantial reduction in weight.
BMI: Current Weight (Kg) / Height (m2). A score below 20 is considered underweight whilst the ideal score is between 20 and 25. A score of 25-30 is considered slightly overweight, 30-35 is considered mildly obese and 35-40 is considered moderately obese. A score above 40 is considered morbidly obese.
Epidemiological studies show the male prevalence of OSAHS is fairly constant and population studies establish the ratio of men to women to be approximately 3:1, respectively. However, the incidence of post-menopausal women is similar to that of men. It is as yet unexplained why men have a greater tendency to develop OSAHS than pre-menopausal women. Men have greater fat deposits in the upper airway than women which might help to explain the difference in incidence. However, anatomically speaking, women have a shorter pharynx than men which may be thought a disadvantage. Currently there is insufficient data to justify the differences between the genders.
Epidemiological studies show that the elderly population suffer more Sleep Breathing Disorders than the young and middle-aged population. The frequency of OSAHS increases with age experiencing a sharp increase after the age of 65.
Studies of sleep breathing disorders in which the genetic component is considered have become increasingly important. In 1995, Redline et al identified the existence of genetic inheritance, discovering that the risk of developing a sleep breathing disorder increased from 2 to 4 times in families where it already existed. Patient questionnaires also reflect the existence of a family background with OSAHS.
Other diseases associated with OSAHS
Certain other medical conditions are clinically associated with OSAHS. These diseases include renal failure and metabolic/endocrine disorders such as acromegaly, hypothyroidism and diabetes type II.
Alcohol and medicines
Alcohol plays an aggravating role in OSAHS. The number of respiratory pauses increases in both snorers and sufferers of OSAHS if alcohol is consumed in the hours just prior to sleep. There is also evidence which shows that many drugs, including sedatives and barbiturates, increase the frequency of apneas. Tobacco and other substances which irritate the mucosa of the upper airway can also provoke more apneas.
Resting position of the head and neck
Body position during sleep can affect the diameter of the upper airway. Resting in the supine position during sleep has a negative effect on the diameter of the upper airway, predisposing to mouth breathing because the tongue and soft palate are displaced backwards. The flexing of the neck also displaces the hyoid bone backwards and provokes airflow resistance. In healthy patients,this position may be the reason for the occasional apneic episode but in OSAHS patients it aggravates the condition.
Posture: The posture adopted and the neuromuscular balance of the head, spine, hips, legs and feet are all intimately linked with the muscles of mastication and the occlusion. Changes in neck position result in a displacement of the hyoid bone, which in turn, alters the airflow resistance in the pharynx. The Temporomandibular Joint (TMJ) connects the lower jaw to the skull and is the guide used by the body to adopt a good posture and is one of the important factors in maintaining balance. When this balance is lost the mandibular condyle adopts a different position within the glenoid fossa.
Nasal breathing is the ideal type of breathing. The other alternative, mouth breathing, is adopted when nasal breathing is not possible due to allergic rhinitis, deviated nasal septum, enlarged adenoids, nasal obstructions or polyps and predisposes the upper airway to collapse.