From the Journals

Sleep apnea factors that may boost risk of heart problems, CPAP response, identified


NEW YORK (Reuters) – In patients with obstructive sleep apnea (OSA), night-time oxygen desaturation and higher heart rate at time of diagnosis were associated with future cardiovascular events in a Chinese cohort study that also suggests a subgroup more likely to benefit from CPAP.

“Despite the obvious and sometimes alarming adverse physiology seen in obstructed breathing events, our knowledge regarding the exact relationship between sleep apnea and potential downstream sequelae on various body tissues/organs is limited,” Dr. Mary Ip of Queen Mary Hospital, University of Hong Kong, told Reuters Health by email. “Gold-standard evidence from randomized controlled studies on cardiovascular protection with treatment of OSA for 3-5 years has not been definitive.

“We observed that nocturnal oxygen desaturation and higher heart rate at the time of sleep apnea diagnosis were better predictors of future cardiovascular adversities than the breathing event frequency – i.e., apnea-hypopnea index (AHI) – which is the currently used indicator for sleep apnea treatment.

“Regular CPAP treatment, while not demonstrating a protective effect in all patients, was associated with fewer major cardiovascular incidents in one out of the four ‘clusters,’ ” she said. Participants in that cluster were “more obese, had very severe sleep apnea, slightly more prevailing cardiovascular diseases (the entire cohort had some CVD background), and were relatively younger, at 50 years old among this late middle-age cohort.”

As reported in Thorax, Dr. Ip and colleagues analyzed electronic health record data for 1,860 Chinese individuals (median age, 52; 67%, women) who underwent polysomnography from 2006 to 2013; 1,544 (83%) had OSA. Patients were clustered according to clinical and polysomnographic features – specifically, by age, gender, obesity, OSA severity, and comorbidities.

Over a median a follow-up of 8.3 years, 278 (14.9%) experienced major adverse cardiovascular events (MACE).

The AHI did not predict MACE (hazard ratio, 0.95). However, sleep time with oxygen saturation <90% (TST90) was an independent predictor of MACE (HR, 1.41), as were wake and nocturnal heart rate.

Among those with moderate to severe OSA (60%), regular CPAP was not associated with a reduction of incident MACE.

As Dr. Ip indicated, in a subgroup (18%) of individuals who were younger, more obese, had more severe OSA (higher AHI and TST90), and more cardiovascular risks, regular CPAP was associated with a lower risk of MACE (HR,0.49).

“Seep apnea patients are very heterogenous. Given their different sleep apnea profiles and diverse clinical characteristics, they may not get the same degree of long-term cardiovascular health sequelae, and some may derive benefit in this aspect from treatment of sleep apnea while others may not,” Dr. Ip noted.

Samuel Krachman, DO, director of the sleep disorders center at the Lewis Katz School of Medicine at Temple University in Philadelphia, commented on the study in an email to Reuters Health. “The findings that the TST90 and nocturnal heart rate and not the AHI predict a major cardiovascular event just adds support to recently done work (demonstrating that) the ‘hypoxic burden’ and the apnea-hypopnea event duration predicted cardiovascular mortality.

“The study shows that we need to focus on variables other than how often patients with OSA stop breathing during the night and more on the physiologic consequences of these events, in particular the hypoxemia, which contributes to vascular changes that occur over time,” he said.

With regard to the subgroup in whom CPAP seemed to reduce the risk for a major cardiovascular event, “we need to be very cautious,” he said. “This is a retrospective study and the group had more associated comorbidities to begin with and also more severe OSA, defined (by) the AHI.

“However,” he noted, “it does support that these types of subgroups need to be studied prospectively to see if treatment and compliance can have a major impact on cardiovascular morbidity and mortality.”

Reuters Health Information © 2022

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