Several cohorts exploring the relationship between OSA and cardiovascular risk were presented during the sleep congress. As a reminder, randomized studies have shown that continuous positive airway pressure (CPAP) does not modify the prognosis of patients. We can assume that the reason is that the patients are in secondary prevention, and that we would therefore intervene too late.
But, it turns out that another important aspect is that patients are treated based on the apnea-hypopnea index. However, American studies have shown that this index is not a good marker of cardiovascular risk. On the contrary, the nocturnal hypoxic load (area under the desaturation curve which follows apneic events) constitutes a much better marker. “This is what we were able to verify in our cohorts, including that of the Pays de Loire, the IRS cohort (1)”, explains Professor Wojciech Trzepizur (Angers University Hospital). This nocturnal hypoxic load indeed constitutes an independent cardiovascular risk factor in these patients.
Nocturnal hypoxic load as a marker of cardiovascular risk
Result, if we reanalyze the randomized studies, we see that, in patients with significant nocturnal hypoxic loads, CPAP reduces cardiovascular risk. For the moment, the hypoxemia threshold above which CPAP is beneficial from a cardiovascular perspective remains to be defined. “But it is a parameter that we will increasingly take into account in clinical practice; in particular to put or not on CPAP a patient with few symptoms, therefore when the main goal is cardiovascular prevention”underlines Professor Trzepizur.
On the other hand, CPAP treatment of symptomatic patients remains the rule, regardless of cardiovascular risk. In this case, CPAP provides a clear improvement in quality of life, not only at night but also during the day, in terms of drowsiness, fatigue, concentration and memory.
Widening of symptoms, particularly in women
A session this year focused specifically on OSA in women. The French definition of OSA, which already dates from 2010, generally describes rather caricatured OSA, very often observed in men with overweight, snoring, daytime falling asleep, etc. However, we realize that women do not necessarily have the same symptoms. They complain more often of fatigue, insomnia or morning headaches. The complaints to be considered are therefore not necessarily the same.
These “new” symptoms were included in the recent revision of the international definition of OSA, broadening the symptomatology associated with OSA. This will need to be taken into account during the upcoming revision of the French definition.
Consider a polysomnography when the polygraphy is negative
On the pathophysiological level, there are also differences between the sexes. Women have more hypopneas than apneas, compared to men. They also have shorter events: their apneas last on average three seconds less. Finally, they have more respiratory events that induce micro-awakenings. However, these events can only be recorded on polysomnographies. This is why we should perhaps give women easier access to this exam.
“More generally, we should not hesitate, in very symptomatic patients, to do a polysomnography when the polygraphy is negative. This is, in fact, what is already recommended in the event of significant discrepancies between symptomatology and polygraphy. notes Professor Trzepizur.
Central apnea and self-controlled ventilation: real symptomatological benefit
Alongside obstructive apneas, representing approximately 95% of cases, there are 5% of central apneas, linked to an interruption of ventilation due to lack of respiratory control. A session was dedicated to them. They are mainly present in cardiac subjects, in particular during advanced heart failure.
Adapted ventilation systems — self-controlled ventilation — were developed several years ago. But they have not shown their benefit on the cardiovascular level. We have even observed excess mortality in severe HF. These systems are therefore contraindicated when LVEF less than 45%. But what about other patients? Should they be treated, and with what objective?
This year, several studies have demonstrated their interest on a symptomatological level. Notably a French registry, highlighting an improvement in symptomatology, but also a Canadian randomized study, which showed that, although there is no benefit on cardiovascular prognosis, we significantly improve not only the quality of sleep and daytime functioning, but also dyspnea linked to HF. These machines have now proven themselves in this regard.
Interview with Professor Wojciech Trzepizur (Angers University Hospital)
(1) Wojciech Trzepizur et al. Sleep Apnea-Specific Hypoxic Burden, Symptom Subtypes, and Risk of Cardiovascular Events and All-Cause Mortality. Am J Respir Crit Care Med 2022 ;205(1):108-117
