Is sleep apnoea a specialist condition? The role of general practitioners

OSA and the risk of accidents

The risk of being involved in a traffic accident is increased six-fold in patients with OSA, and furthermore this possibility is doubled in combination with alcohol consumption [5]. Similarly (although there are fewer studies in this respect), there is an increased risk of accidents in the home and workplace [9]. It has been observed, however, that treatment with CPAP is capable of reversing this situation almost to a normal level [12].

OSA and cardiovascular disease

There is an ever-growing body of evidence to show that OSA can provoke certain cardiovascular diseases or worsen their prognosis. This association seems to be based largely on physio-pathological factors, as patients with OSA display almost all the classic intermediate mechanisms capable of giving rise to a cardiovascular disease: arteriosclerosis, systemic inflammation, hypercoagulability, sympathetic activation and other metabolic events [8].

OSA and arterial hypertension

This is probably the association that has been found most consistently, and studied most comprehensively. Studies with a very high level of evidence confirm, in keeping with the majority of the most widely recognised international guidelines on the subject, that OSA is an independent risk factor for arterial hypertension [13]. Furthermore, several recent meta-analyses and studies verify that treatment with CPAP is capable of significantly reducing blood pressure [14, 15].

OSA and ictus

Patients with OSA have a two- to three-times increased risk of suffering from an ictus [10]; this relationship also seems to be present even in the absence of arterial hypertension, probably on account of other intermediate mechanisms such as cardiac arrhythmias, hypercoagulability and arteriosclerosis. Moreover, the presence of untreated OSA in patients who have previously experienced an ictus appears to be associated with a greater risk of suffering from a further ictus [16], as well as with impaired functional recovery [17] and greater excess mortality [18]. Some observational studies have also established that treatment with CPAP is associated with a lower risk of an ictus, a new cardiovascular event or death in patients who have previously suffered a cerebrovascular event and present an excess of sleep respiratory disturbances [19].

OSA and ischaemic heart disease

Some authors have used population studies to warn that patients with OSA present a two- to threefold increase in the prevalence of ischaemic heart disease [20]. Research on the effect of treatment with CPAP on these patients is in progress.

OSA and heart failure

OSA has a two-pronged relationship with severe heart failure. On the one hand, OSA can trigger a reduction in the ejection fraction of the left ventricle and, on the other hand, the presence of a heart failure, whether systolic or diastolic, increases the probability of central respiratory events, which, in turn, intensify the disturbance in the left ventricle, thereby closing the pathogenic vicious circle [21]. Although CPAP does not appear to improve mortality in patients with heart failure and central sleep apnoea (Cheyne–Stokes breathing), it may be effective in the evolution of patients predominantly subject to obstructive events [22].

OSA and mortality

Several studies with an extensive follow-up conclude that the presence of untreated OSA produces excess mortality, both in general and, more especially, from cardiovascular causes, and this seems more evident in individuals aged <50 yrs [11, 23]. Treatment with CPAP seems to reduce the excess mortality observed in patients with OSA, especially when it is related to the cardiovascular system [24].

OSA and quality of life

OSA – especially in its most symptomatic forms – lowers quality of life in health terms in patients of all ages, although this phenomenon is more evident in middle-aged individuals with an active social and working life [4]. Treatment of these serious forms of OSA with CPAP clearly improves patients’ quality of life, to the point of attaining values similar to those of individuals of the same age and sex who do not suffer from the disease [25].

Other associations

Other diseases or cardiovascular risk factors associated with OSA are cardiac arrhythmias (unsustained ventricular arrhythmias and auricular fibrillation), pulmonary hypertension, metabolic syndrome, insulin resistance and diabetes [8].

Prevalence of OSA symptoms in primary care

If, as mentioned above, OSA is a very prevalent disease, it is obvious that its risk factors, or the presence of symptoms and signs related to it, are even more widespread. The prevalence of symptoms related to OSA, and of sleep disorders in general, in patients who see their PCP for whatever reason is far higher than the prevalence of these symptoms in the overall population of the same sex and age range. This can be explained by the characteristics inherent to this sub-group of the population, which is generally older, more obese and subject to a greater number of comorbilities, especially of a cardiovascular and neuropsychiatric nature, all of which have been related to a greater probability of suffering from OSA. Netzer et al. [34] observed, when they analysed 744 patients attending a primary care centre, that 52.2% presented chronic snoring (in 24.6% this was extremely noisy), that 47.9% snored over three times a week and that 11.1% experienced witnessed apnoeas. The authors concluded that 37.5% of the individuals analysed presented a high clinical probability of OSA, and that 18.4% experienced sleepiness while driving and were therefore clearly candidates for referral to a sleep unit [34].

Suspicion of OSA in primary care

Despite the fact that in the past decade there has unquestionably been an overall increase in the number of diagnoses of OSA subsequently referred to sleep units [35], both from primary care and from other areas, various studies show that there is a clear failure to suspect the incidence of OSA in primary care. This is one of the reasons why 90% of patients with OSA still go undiagnosed, and why PCPs refer only a small percentage of the patients they see in their consulting room. Several determining factors seem to foment this situation. The data presented below are entirely based on research studies.

Deficient compilation of a clinical sleep record

Only 6% of the medical histories compiled in primary care make explicit reference to possible problems during sleep in a population in which, as mentioned above, >30% of individuals present risk factors for OSA. Only 10% of PCPs ask at least two questions related to sleep in standardised patients at a normal appointment covered by researchers [36]. Namen et al. [37] observed that, despite a written or verbal note from the researchers to include data concerning the quantity or quality of their patients’ sleep, staff in primary care did not collect data on sleep-related diseases in >80% of individuals, even though they did collect, spontaneously and without any need for a reminder, data on smoking and alcohol. Furthermore, even in the 15–20% of medical histories that did feature sleep-related data, only 11% of these (1% of the overall total) considered the data collected worthy of examination and therefore integral to a doctor’s arrival at a diagnosis. Virtually none of the histories presented any written advice or treatment related to sleep in general, or sleep apnoea in particular, and once again this percentage was much lower than that observed for other public health problems such as obesity and smoking. This failure to collect data or give therapeutic advice was equally apparent with individuals with a high clinical probability of suffering from OSA. The failure to collect data was especially striking in the case of snoring and led the authors to deduce that the PCPs do not consider this phenomenon to be a potentially pathological entity [37].

Referral of only the most typical forms of the disease

Kramer et al. [38] observed that 96% of patients referred from primary care to specialised care are diagnosed as suffering from OSA. In a high percentage of these patients, the OSA was severe (mean AHI 44.2 h⁻¹) and highly symptomatic (manifest obesity (body mass index (BMI) 37.9 kg·m⁻²); chronic snoring (93%); excessive hypersomnia (91%) and witnessed apnoeas (64%)). The authors concluded that only those patients with a very clear phenotype are referred, and that this does not apply to untypical but very common phenotypes, particularly those related to the cardiovascular system, in women and the elderly [38].

Referrals made mainly by a small number of PCPs

One of the other conclusions reached by Kramer et al. [38] was that the majority of referrals are made by a limited number of PCPs. Thus, 72% of the participating PCPs referred only one patient, which means that the remaining 28% referred 80% of the patients. The explanation for this discrepancy probably has something to do with heightened awareness of the subject among some professionals, or more comprehensive training/retraining. Similar results were obtained by Namen et al. [37] when they put a reminder about collecting sleep data into clinical histories; this was only taken up by 30% of the participants, who happened to coincide with the ones who made the majority of the referrals to a sleep unit for suspicion of OSA [37, 38].

Referral of a very low percentage of patients

As Netzer and co-workers [34, 39] have shown, even though at least 30% of the population seeing a PCP present criteria for referral to a sleep unit, the total percentage of referred patients is very small [34, 39]. Kramer et al. [38] observed that, despite the use of a written reminder from researchers, only 0.13% of the monitored patients were referred. A similar figure (0.27%) was reported by the Walla-Walla Project, a training programme undertaken in Washington State, USA [40].

Lack of knowledge of OSA and its consequences

Although lack of knowledge of this pathology is found in every field, it is not found everywhere in equal measure. Most PCPs still consider snoring as a normal situation that coincides with obesity, and daytime hypersomnia as a banal occurrence attributable to age or the medication being taken by the patient. As a study by Chung et al. [41] has shown, there is an even greater lack of knowledge of those aspects that have only recently come to light, such as the relationship between OSA and cardiovascular problems and the notion of treatment with CPAP – considered a “treatment for specialists” by PCPs – as a way of solving problems [41].

Relative “youthfulness” of OSA as a disease

The relationship of smoking and lung cancer, or that of arterial hypertension and cardiovascular events, has been an uncontested given for many decades and so neither the general population nor PCPs could ignore them. OSA is, however, a “young” disease, as the extent of its potential to provoke devastating effects on general health was only discovered a few decades ago. This has meant that the training programmes followed by most PCPs of a certain age did not contemplate this disease, and neither have retraining courses of sufficient quality been set up. Even younger doctors have not spent more than a few hours of training in OSA on their university courses, which translates into the scanty collection of sleep-related data in the medical histories they compile during their residency.

Lack of knowledge of OSA on the part of the general population

Finally, there is another vital element that is also missing: knowledge of OSA and its consequences among the general population, as well as awareness of the availability of highly effective treatment. It is difficult to raise awareness in this respect as people traditionally consider the typical symptoms of OSA as normal occurrences that come with age, or with excess weight or the amount of medication they are taking; this means that they do not seek medical advice. Bartlett et al. [42] carried out a study on the general population by sending a letter to 10,000 individuals from the census. These were answered by 35.6%; the prevalence of snoring plus witnessed apnoeas, which would indicate a high clinical probability of OSA, was 6.2%, but only 2.9% consulted a doctor for this reason (without any significant differences for sex).

Acquisition of knowledge and regular retraining

Recent studies have shown that, despite the fact that suspicion of OSA is one of the most frequent reasons for referral to a respiratory disease specialist, there is a low degree of clinical suspicion on the part of PCPs [45, 46]. This is probably due to the relative scientific youthfulness of this disease, limited access to well-grounded information and the belief that key symptoms of OSA, such as chronic snoring and hypersomnia, can be caused by problems deemed unworthy of referral. So the prototypical referred patient tends to correspond to the most typical forms of OSA [38], which means that the atypical forms – those related to cardiovascular manifestations, and even OSA in women – go more unnoticed. Furthermore, a limited number of PCPs – probably those with the greatest awareness of the subject – are responsible for most of the referrals that are made. This makes it essential for primary care staff to commit themselves to high-quality training/retraining in sleep problems in general, and in OSA in particular (figure 1).

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Figure 1

Functions and obligations of primary care and sleep units with respect to the handling of patients with OSA, or suspected of having OSA.

Detection of cases

It has been estimated that up to 80% of individuals see their PCP at some point, and most of these do so several times over the course of a year. These occasions, regardless of the reason bringing the individual into the consulting room, are ideal for asking patients a few quick, simple key questions (table 3) that provide clues as to the need to keep on probing (table 4), just as questions are asked for a medical history about whether patients smoke or have smoked in the past, or whether they suffer from hypertension.

Prioritisation and protocolisation of referrals

One fundamental aspect of a PCP’s task is to know how, and with what degree of priority, to refer a patient. This makes it essential to have a simple, informative protocol for referral that does not take up too much time, is based on a mutual agreement between PCPs and a sleep unit and covers the basic characteristics of a patient suspected of having OSA. This protocol must be complete enough to make it possible to classify a patient as having a high, medium or low clinical probability of OSA and, acting on this information, allow a PCP to refer a patient to a sleep unit on an ordinary, preferential or urgent basis (figure 2).

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Figure 2

Protocol for referral of OSA in primary care

Handling of general treatment and basic problems with CPAP: CPAP is not a specialist treatment

Despite received opinion to the contrary, CPAP is not a specialist treatment. The large number of patients now equipped with this device, and the ease with which many of their problems can be solved, means that most sleep units do not have sufficient capacity or time to tackle this problem and so a PCP has to be involved. He or she must try to solve some of the most common adverse effects of CPAP, while also being aware of when it is necessary to send a patient to a sleep unit to deal with other more serious adverse effects, or a lack of any effect at all from the usual treatment (table 5).

Follow-up of patients with OSA or risk factors for suffering from it

Once a patient has been diagnosed with OSA, with or without treatment with CPAP, or has been established as having risk factors for OSA without actually having the disease, a PCP must instigate a regular follow-up in order to evaluate certain factors:

• Adverse effects of CPAP. Either for an immediate solution or to refer a patient to the corresponding sleep unit (table 5).

• Non-compliance with the treatment. Search for the cause, referral if necessary.

• Changes in the risk factors for OSA, with special attention to changes in weight or treatment with psychotropics (table 6).

• Reappearance of symptoms of OSA, despite the application of treatment (table 7).

• Medical advice on diet and sleep hygiene (table 8).

Health promotion

One of the key aspects of handling OSA is information for the general population. A PCP must inform the public about OSA from a general viewpoint, with a special emphasis on the risks associated with it and the alarm mechanisms that should occasion a visit to the doctor. As a result of the high frequency in the general population of the symptoms and signs of OSA – such as chronic snoring, hypersomnia and obesity – these symptoms can pass unnoticed or can be accepted as normal or the result of ageing, and are consequently not reported to a doctor. At the present time this is probably the most significant reason for the lack of diagnosis.