The Sleep Apnea-Hypoapnea Syndrome (SAHS) is characterised by a repeated occlusions of the upper airways during sleep, that provoke constant oxyhaemoglobin desaturation and transitory disruptions of sleep. These transitory disruptions are responsible for the fragmentation of sleeping patterns and, as a consequence of a lack of revitalising sleep, are the cause of excessive daytime somnolence. The SAHS has been associated by several authors with a greater incidence of cardiovascular diseases and traffic accidents.
SAHS is highly prevalent. According to a number of different studies, between 2.2 and 6% of men and between 0.8 and 2% of women in the general adult population suffer from this syndrome. This may affect between 1 and 3% of children. The high prevalence of this disorder and the improvements attained in the attention given to this in the Basque health service suggest that there will be an important increase in the demand for medical care, with major repercussions of both an economic and organisational nature.
Analysis of the scientific evidence
The first part of the survey consisted of an analysis of the scientific evidence. On the one hand, a study was made of the relationship between SAHS and the increased risk of cardiovascular diseases and traffic accidents and on the other, the effectiveness of the different treatments.
Cost effectiveness analysis
A cost-effectiveness analysis has been made by means of the construction of a Markov model which represents the natural history of SAHS. The model reproduces the changes implied by SAHS in terms of quality and life expectancy and compares the two options. On the one hand, the treatment of SAHS by means of CPAP, as practised in the Sleep Unit of Txagorritxu Hospital, and on the other the alternative that consists of allowing patients to continue developing naturally without treatment. The effectiveness and cost of both alternatives have been calculated and a comparison has been made of these by means of the cost-effectiveness ratio.
To conclude, the study contains an analysis of the sensitiveness, according to age, sex and utility, of treatment with CPAP.
In the search of the bibliography on this subject, 13 clinical tests were found. On analysing these, it has been seen that they involve considerable methodological restraints and problems. On the one hand, they are not based on a common definition of the illness, they are all of short duration and the number of patients is small is each case. On the other hand, the instruments used to measure results vary in the studies of one group of researchers and another. Some studies mix patients with different levels of acuteness, and there are no multi-centre surveys. In spite of the limitations commented on, treatment with CPAP reduces somnolence in patients as well as improving their quality of life.
There are no clinical tests to analyse the long-term impact of treatments of SAHS with regard to cardiovascular illnesses or accidents. Given that there are several observational studies that tackle these issues, we have based our study on these in order to calculate the impact the CPAP treatment has on the life expectancy of these patients as a consequence of the lower level of risk of cardiovascular illnesses and traffic accidents.
The results of the cost-effectiveness study show that for a typical patient, a male of 55 years of age, treated until his death with CPAP, the cost per Quality Adjusted Life Year (QALY) gained is 1,923,422 pesetas (11,560 Euros). In the sensitivity analysis, by varying different variables, the cost-effectiveness ratio is between 3,000 and 17,000 Euros per QALY. For this reason, it is considered that the treatment of severe SAHS is a cost-effective practice when compared to other widely used treatments such as the treatment of hypertension or fibrinolysis, as the cost-effectiveness ratio values are very much lower than the figure of 20,000 Euros/QALY.
The key factor, and, therefore the one that justifies treatment with CPAP, is the improvement in the quality of life of patients with SAHS, as it provides an incremental effectiveness 12 times bigger that the improvement of cardiovascular risk and 82 times bigger that the risk of traffic accidents.
Mandibular advancement prostheses are considered to be a promising treatment but even more studies are required before they can be recommended generally. Studies have demonstrated that their efficiency is inferior to that of the CPAP. On the other hand, they seem to be more efficient in patients with severe SAHS and obesity. For this reason, these are a second line of treatment for patients who do not tolerate the CPAP and if the studies currently under way show this, they could be used in slight to moderate cases of SAHS.
We recommend the use of the CPAP for patients with Apnea and Hypoapnea Index (AHI) measurements equal to or higher than 30 and with severe clinical pathology or associated comorbility.
With regard to the other options of alternative treatment, drugs or surgery, it is considered that there is not sufficient evidence to advise on their use, and so it is recommended that the use of these options be restricted to the context of clinical trials.