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Breathing disturbances during sleep as a risk factor in aging persons Torna agli editoriali

Anna Giulia Cattaneo,DBSM

Sleep-disordered breathing (SDB) and obstructive sleep apnoea syndrome (OSAS) are supposed to be common disorders, mainly associated with obesity and male sex.
The whole complex of symptoms has been known from centuries, at least in some aspects. The "Pickwickian syndrome", i.e. the association of obesity, the habit of suddenly falling asleep during the daytime and snoring, derives its name from the Dickens novel, in which the syndrome has been appropriately described more than a century ago as a character, without any medical pretension.
Both disorders involve poor sleep quality: frequent sleep disruption follows episodic apnoeas or hypopnoeas. These lasts represent the characterizing traits of the disease, whose prevalence should approximate 27% for SDB, and 7 % for OSAS, in middle and aged subjects from a white general population of western countries. The prevalence of most severe syndrome, with narcolepsy and hypercapnia, has been estimated to be 4% in men and 2% in women. Obesity, male sex and aging are independent predictors.
When the disorder reaches its most severe degree, hypoventilation during sleep causes desaturation of oxyhemglobin, and in turn polycythaemia and daytime sleepiness. At that point the syndrome shows its more severe, even life threatening aspect, being both SDB and OSAS predictors of cardiac disease, independently from BMI, sex and smoke habits.

Despite of the long-lasting knowledge of the main symptoms, an adequate diagnosis requires the help of modern technologies, in particular of the polysomnography that remains the only accurate diagnostic means.

The subjects are examined during a normal sleep cycle: the level of haemoglobin desaturation in the precapillary blood (pulse oxymetry) is recorded at the same time of electroencephalogram, electrocardiogram, electromyogram and respiratory movements and air fluxes. This complex of data is aimed to detect sleep phases and awakenings periods, haemoglobin desaturation during the sleep time, and apnoeic or hypopnoeic phases; several other measures can be added to explain physiopathology or to obtain more simple, predictor values. The procedure is better tolerated than supposed by description, however it requires a special equipment and environment, consisting in a calm room, isolated from external sounds and comfortable enough to avoid environmental sleep disturbances, immediately adjacent to the recording room, where the polysomnography apparatus and the equip are at work. This technique, while expensive, is essential to pose a correct diagnosis, to distinguish between SDB and OSAS and to evaluate the severity of the disturbance, usually given as the Apnoea/Hypopnoea Index (AHI, number of episodes per hour of sleep).

A brief summary of conditions underlying and even causing the disorder include the amount of intraddominal fat (possibly derived indirectly by the measure of the Body Mass Index and of waist circumference), the trophism of respiratory muscles, and the shape of the neck and of the pharyngeal area. The pharyngeal narrowing, studied by fiberoptic scopy during the Muller manoeuvre, seems to be an important predictive parameter for risk of sleep apnoeas, especially at the retroglossal and retropalatal level.

Obesity, diabetes mellitus with autonomic neuropathy, and hypertension (especially if a multidrug treatment is required) are recognized risk factors or pejorative associated conditions for sleep apnoeas.

Aging is per se a risk factor for either SDB or OSAS. The reduced elasticity of tissues (particularly at the level of pharyngeal and laryngeal cartilages) and the decay in muscle trophicity, in this case of the pharyngeal and respiratory districts, play a role in promoting disturbed breathing during sleep and even obstructive apnoeas.
The enhanced prevalence later in life of the over mentioned risk factors should be added to the physiological decay of the respiratory apparatus; the higher prevalence of hypertension and complicated diabetes mellitus, and the deregulation of autonomic nervous system activity possibly is sustained in older persons by a number of different conditions being among the most relevant. To all that, the additive deleterious effects of smoke habits and the Chronic Obstructive Pulmonary Disease (COPD) should be added, as factor whose importance in aggravating the risk for OSAS is increased in aging. The role of this last condition as a risk factor for SDB or OSAS is discussed, however a special attention should be paid to subjects having a moderate to severe degree of daytime hypoxemia, in which prednisolone could be of help to reduce the additive effect of sleep apnoeas, when present.

Sleep apnoeas seems to be more frequent in older subjects with cognitive impairment, and in those surviving a stroke. These last suffer often from central sleep apnoeas, in addition to obstructive sleep apnoeas. A recently published follow-up (Arch.Intern.Med 168: 297-301, 2008) conducted on a large group of these subjects over ten years, with death as the only cause for dropping-out, permits to identify the obstructive sleep apnoeas as a risk factor for death independent from all other risks. On the contrary, the central sleep apnoea, following lesions of selected region in the brain, does not involve obstruction of airways, nor significantly enhance the risk of death.

The detrimental aspects of SDB and OSAS on the quality of life are more severe in the aged persons, proportionally to the degree of nocturnal arousal following apnoeic episodes, to increasing daytime sleepiness or even narcolepsy: headache, mental impairment, depression and social inadequacy follow. The frailty of the older persons enhances the risk for life threatening cardiac disturbances, mainly nocturnal arrhythmias and cardiac failure. Hypercapnia increases the risk for cerebral oedema and stroke.

Preventive measures can be applied at different levels: first help will derive from adopting simple but accurate hygiene of the sleep habits: bed rest should be at regular time, not too prolonged nor permitted to watch TV or read; positions different from lying on the back should be preferred. Alcohol and sedative should be avoided in the evening, while exposure to mild and comfortable light before sleeping should be of help. In addition, nasal cavities should be maintained decongested and smoke habits reduced. Painful conditions adequately treated. All these measures should be applied as beneficial to all aged person, living at home or in assisted facilities and independently from the presence of breathing alterations during the sleep time.

Attention should be paid in identifying at risk subjects, in which a selective and more accurate study should be appropriate. The evaluation of excessive daytime sleepiness on the basis of convalidated questionnaires is a very affordable screening procedure, which can be performed by the patient itself or by non professional care-taking. An excellent starting point should be the anamnestic recordings of sleepiness following two types of questionnaires, the Epworth Sleepiness Scale (ESS) or the Stanford Sleepiness Scale (SSS): both are easily understandable and available even online at the site of many educational institutions, both for patients and nurses. While polysomnographic recording remains the only means to pose a correct diagnosis, it could be too challenging to be proposed for wide diagnostics in geriatric care, and reserved instead to selected cases. An appropriate means to check the risk of nocturnal oxyhemoglobin desaturation and of hypercapnia is represented by the pulse oxymetry. This non invasive and not too expensive procedure could be taken into account for a larger diffusion as a diagnostic mean both in rehabilitation facilities and in nursing homes: low levels of oxyhemoglobin during the sleep time could be a useful marker for at risk individuals, requiring supplemental diagnosis and care.

When necessary, the treatment should be directed on resolution of underlying or associated conditions, like reduction of body weight excess, as convenient, or an early and adequate control of diabetes and its sequel. Apnoeic accesses during the sleep time can be prevented by applying a positive airway pressure: far from being only a symptomatic measure, this procedure can significantly reduce the cardiac risk and consistently ameliorate the welfare. This seems to be the most simple and affordable method; other treatments, as surgical interventions on the airways, devices for mandible advancement, or drugs acting on serotonin reuptake and antidepressant, seems to be poorly suffered, and of very limited benefit, if not even detrimental, when used in older people.

Anna Giulia Cattaneo, DBSM, Università dell'Insubria, Via J-H Dunant,3 - 2100 Varese

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