Studies examine link between CPAP treatment, CV outcomes in adults with obstructive sleep apnea

Two studies recently published in the Journal of the American Medical Association investigated the effectiveness of reducing the risk for CV outcomes using continuous positive airway pressure in adults with obstructive sleep apnea.

For one study, José M. Marin, MD, and colleagues examined 1,889 participants without hypertension who were referred to a sleep center for nocturnal polysomnography from 1994 to 2000. Incident hypertension was documented at annual follow-up visits through January 2011.

Of patients enrolled, 37.3% developed incident hypertension during 21,003 person-years of follow-up. After including change in BMI as a covariate in the fully adjusted model, risk for incident hypertension remained 33% greater among patients with obstructive sleep apnea who were ineligible for CPAP therapy (HR=1.33; 95% CI, 1.01-1.75); risk was nearly two times as high for patients who declined CPAP therapy (HR=1.96; 95% CI, 1.44-2.66); and risk was about 80% greater among patients who were nonadherent to CPAP therapy (HR=1.78; 95% CI, 1.23-2.58), compared with controls without obstructive sleep apnea. In patients with obstructive sleep apnea who were treated with CPAP therapy, the risk for incident hypertension was lower than in controls (HR=0.71; 95% CI, 0.53-0.94).

“Although CPAP therapy was not allocated randomly to our patients, the associated lower excess risk of hypertension strongly suggests that obstructive sleep apnea may be an independent modifiable risk factor for development of new-onset hypertension. The observed correlation between severity of obstructive sleep apnea and the magnitude of risk for hypertension further supports obstructive sleep apnea as a major contributor to CV risk,” Marin and colleagues wrote. “In conclusion, compared with participants without obstructive sleep apnea, untreated obstructive sleep apnea was associated with an increased risk of new-onset hypertension.”

No major effect of treatment found

In the second study study, Ferran Barbé, MD, of the Coordinator Center in Lleida, Spain, and colleagues randomly assigned 357 patients with obstructive sleep apnea to treatment with continuous positive airway pressure (CPAP) and 366 to no active treatment between May 2004 and May 2006. Researchers evaluated patients at 3, 6 and 12 months and annually after that; follow-up ran until May 2009. Primary outcome measures included incidence of either system hypertension or CV event.

During a mean follow-up of 4 years, more patients in the control group developed new hypertension (n=79) vs. the CPAP group (n=68). These results were similar among patients who developed CV events (31 in control group vs. 28 in CPAP group). Incidence density rate for hypertension or CV events was 9.2 per 100 person-years (95% CI, 7.36-11.04) in the CPAP group vs. 11.02 per 100 person-years (95% CI, 8.96-13.08) in the control group. Study results showed an incidence density ratio of 0.83 (95% CI, 0.63-1.1).

However, the researchers noted that the study may have limited power to detect a significant difference, and that a larger study or longer follow-up might have been able to identify a significant association between treatment and outcome. They said: “A post-hoc analysis suggested that CPAP treatment may reduce the incidence of hypertension or CV events in patients with CPAP adherence of 4 hours/night or longer.”

Questions remain

In an accompanying editorial, Vishesh K. Kapur, MD, MPH, of the department of medicine and sleep center, and Edward M. Weaver, MD, MPH, of the department of otolaryngology-head and neck surgery and sleep center, both at the University of Washington, Seattle, said, “although these studies significantly advance the understanding of the positive relationship between obstructive sleep apnea and incident hypertension and the benefit of CPAP therapy, many questions remain regarding obstructive sleep apnea, hypertension and treatment.”

For more information:

Barbe F. JAMA. 2012;307:2161-2168.

Kapur VK. JAMA. 2012;307:2197-2198.

Marin JM. JAMA. 2012;307:2169-2176.

Disclosure: The research was supported by resources from the Veterans Affairs Puget Sound Health Care System, Seattle, and by a grant from the NIH. Drs. Barbe, Marin and Weaver reports no relevant financial disclosures. Dr. Kapur reported having owned stock within the past 3 years in Merck, Johnson & Johnson and Bristol-Myers Squibb.