Sleep apnea: towards precision medicine

18 Jan
Ferran Barbé

Obstructive sleep apnea is a chronic disorder characterised by recurrent episodes of a blockage of the upper airways during sleep which affects between 5% and 14% of adults from 30 to 70 years of age, mainly men. In addition, sleep apnea leads to a reduction of the intake of oxygen (hypoxia) during sleep. In order to counteract this lack of oxygen, the brain reacts by forcing a short awakening known as arousal which reactivates the muscles in the upper airway and allows air to pass through (reoxygenation).

These cycles of hypoxia-reoxygenation produce stress to the circulatory system and leads to an increase in the risk of cardiovascular, hypertensive, metabolic, cerebrovascular, or neoplastic diseases, and lastly, a risk of death. At the same time, the arousals prevent a person from having a good night’s rest, produce the feeling of tiredness and an excessive desire to sleep during the day, which is associated with an increase in road accident rates and a decrease in life quality.

A standardised approach in the treatment of sleep apnoea exists: the use of continuous positive airway pressure (CPAP) during the night in order to keep the upper airways open which helps the person rest.

However, treatment with CPAP shows contradictory results. On the one hand, it has been demonstrated that the use of a CPAP for at least 4h per night increases quality of life and reduces blood pressure among population groups with high blood pressure. In contrast, it has not been demonstrated that the use of CPAP reduces the risk of major cardiovascular events or deaths. Therefore, sleep apnea is a heterogeneous disorder and the use of CPAP is not equally effective with all patients. Which patients can benefit most from the treatment? Should all patients be treated in the same way?

We believe it is important to look for patients with sleep apnea profiles that can benefit from a treatment with CPAP. The creation of the PADRIS programme (Public Data Analysis for Health Research and Innovation Programme in Catalonia), whose aim it is to make related health data available to the scientific community to drive research, innovation and assessment in health, has given us the opportunity to be able to analyse all subjects with sleep apnea treated with CPAP in Catalonia. We are talking about 71,217 people, approximately 1% of the general population who were attended by the public health system in Catalonia (primary care, hospital care, social health and/or pharmacy) in the period 2012-2013.

To establish these profiles (that is, groups of patients having similarities with each other but at the same time very different from the remainder) the most frequent comorbidities of patients with sleep apnea have been taken into consideration as well as the clinically relevant comorbidities. Six different profiles of patients were identified among patients with sleep apnea and treated with CPAP in Catalonia.


Despite defining these six different patient profiles, we can safely say that the population of Catalonia receiving CPAP is divided into two large basic groups: on the one hand, old age patients, with a high mortality rate and a frequent use of resources, and on the other, patients with fewer comorbidities, a low mortality rate and an infrequent use of resources. You can read it in an article in Plos ONE.

Do both groups need to be treated in the same way? It seems not. In the group with fewer comorbidities, a low mortality rate and an infrequent use of resources, it seems that sleep apnea is the most important determinant in the prognosis of these patients and there is evidence that this would be the group that could most benefit from treatment with CPAP. In contrast, it seems that in the other group sleep apnoea is at a secondary level, given that the predominant diseases are more serious.

The study has allowed us to assess the association between treatment with CPAP and mortality; that is, whether more people die who are being treated with CPAP or whether more people die having the same comorbidities but without sleep apnea.

To be able to achieve this objective, for each patient treated with CPAP we looked for three people with similar characteristics but without sleep apnea. What we observed was surprising, namely that despite presenting a greater number of comorbidities, treatment with CPAP is associated with a decrease in mortality rate at a population level (Am J Crit Care Med 2018).

We now need to continue working to find out what occurs in each of the patient profiles. Having access to this volume of data helps us to make an estimate of the groups of patients with sleep apnoea that will benefit more with CPAP treatment and this means that we are getting closer and closer to precision medicine.

Diseases do not exist, ill people do

Post written by Ferran Barbé, Hospital Institut de Recerca Biomèdica de Lleida.

Crisis, inequalities and policies: proposed intinerary

7 Sep

Unfortunately, inequalities in health are still an issue today including in our country. The crisis of recent years has once again put the spotlight on this subject.

 This is why we propose an itinerary taking us through the different texts which we have published on the subject in this blog and, in particular, we invite you to read the original texts which are mentioned here in more depth, a large proportion of which have been elaborated at the AQuAS.

In September of last year, Luis Rajmil reflected on social inequalities in child health and the economic crisis in this post placing the concepts of equality, equity and reality  on the agenda for discussion.

 “At present, there is enough accumulated information that shows that life’s course and the conditions of prenatal life as well as life during the first few years are very influential factors in the health and social participation of an adult to come.”

At a later date, the Observatory of the effects of the crisis on the health of the population published its third report but prior to that, a post was published with a collection of individual thoughts and reflections on this subject by Xavier Trabado, Angelina González and Andreu Segura focussing on, respectively, the effects of the crisis on the mental health of people, the coordination of different mechanisms in primary and specialised care, the urgency for community health actions and the need to engage in intersectoral actions.

 “It is urgent to put community health processes into action; processes in which the community is the protagonist, which constitute the shift from treating an illness to a bio-psycho-social approach which gives an impulse to intersectoral work in a network with local agents, with who there is the shared aim of improving the community’s well-being. Based on the needs detected and prioritised in a participatory way and with the local assets identified, these processes activate interventions based on evidence which are assessed”

In this other post, Cristina Colls presented an interesting case of the application of scientific evidence to political action which occurred with the revision of the socio-economic dimension of the formula for allocating resources to primary care.

 “Social inequality leads to an unbalanced distribution of the population in a territory, concentrating the most serious social problems in certain municipalities or neighbourhoods having higher needs for social and health services than other territories. In this context, more needs to be done where needs are greater if the aim is to guarantee equality in the allocation of resources”

Finally, the most recent post was written by Anna García-Altés and Guillem López-Casanovas. It is a text that provides food for thought based on the latest report published from the Observatory of the Health System of Catalonia on the effects of the crisis on the health of the population.

 “Understanding the mechanisms  by which social inequalities have an impact on the health of the population, so as to know how best to counter or neutralise them, in any place and at any time, is an issue that must still be addressed by our social policies”

We hope that you this very short itinerary through these texts, initiatives and analyses that aim to be useful in tackling inequalities has been of interest.

Post written by Marta Millaret (@MartaMillaret)

An indicator for a more fairly funded primary care

7 Apr
Cristina Colls

The Catalan government has recently expressed its willingness to increase the importance ascribed to the socio-economic level of regions when calculating the budget for each primary care team.

This fact invites us to ask ourselves a question: why is it important to bear in mind the economic inequality in the funding of primary care teams?

The influence of socio-economic inequalities on the health of the population is a fact that has been widely studied since the 60s of last century and of which there is evidence both in the international and national context.

We know that people with a lower socio-economic status have more probability of dying before the age of 65 and that they show more physical and mental health problems during their lives. It is logical, therefore, to conclude that they need to make a more intensive use of health resources.

We also know that social inequality is a recipe for an unbalanced distribution of the population in a territory leading to an accumulation of the most serious social problems in specific municipalities or neighbourhoods that have a greater need for social and healthcare than other regions.

It is in this context that more needs to be done where there is greater necessity if equity in the allocation of resources is to be guaranteed. But where should more resources be provided?

The professionals of primary care teams are those closest to the citizen and therefore, have a comprehensive view of the health needs of the population in their territory.

In addition, the primary environment is the reference in prevention activities, in controlling chronic diseases and from which a large part of community activity is coordinated. For all these reasons, the provision for primary care teams must bear in mind the socio-economic conditions of the population they serve.

How can we find out what the socio-economic situation is of territories in which a primary care primary care team works? Many variables exist which give us indirect information (income, occupation, education, housing conditions, among others) but if we are looking for only one classification we need a unique index that synthesises all these aspects; it is what we call a deprivation index.

Deprivation indexes have been widely used as a tool in social policies because they allow an objective prioritisation to be established in small regions, ranging from a low to high socio-economic status. The concept of “deprivation” refers to unmet needs as a result of a lack of resources, not exclusively economic.

All indexes of deprivation are built by adding up the results of different socio-economic status indicators. The weight given to each indicator could be theoretical, that is, based on what a particular indicator is thought to contribute to the phenomenon of deprivation; or otherwise, the result of a multivariate statistical model.

To be able to classify the basic areas of health (reference territories of a primary care team) according to their socio-economic level, AQuAS has built an index called a composite socio-economic status indicator which synthesises seven indicators: population exempt from drug co-payment, population with incomes lower than 18,000€, population with incomes higher than 100,000€, population with manual jobs, population with insufficient educational attainment, premature deaths or potentially avoidable hospitalisations.

The statistical methodology used for calculating this indicator has been that of principal component analysis. The application of this methodology has allowed us to obtain a socio-economic status map of Catalonia.

The application of the composite socio-economic status indicator has been done within the framework of the redefinition of the model of allocation of resources for primary care and has enabled the identification of those primary care teams which will increase their budgets in coming years.

This new model of allocating resources for primary care is an experience in applying scientific evidence to political action.

Post written by Cristina Colls.