In a second study appearing in the same issue, Dr Apoor S Gami et al (Mayo Clinic, Rochester, MN) report that people with obstructive sleep apnea (OSA) are more likely than people without OSA to have a family history of premature death from CAD [2]. As the authors note, OSA has been proposed as an independent risk factor for CAD morbidity and mortality, but the link between the two is not well understood.

"A family history of premature CAD reflects a number of unknown genetic and potentially environmental influences on CAD risk, and it has been shown to be an important and powerful risk factor for CAD," Gami explained to heartwire. "The principal finding of this study is that individuals with OSA are more likely, regardless of their own history of CAD or its risk factors, to have a family history of death related to premature CAD. Never before has the relationship between OSA and this CAD risk factor been assessed. The discovery of this association is important because it highlights the possibility that individuals with OSA are at an increased risk of CAD via factors that are not traditionally assessed and potentially via inheritable mechanisms that are yet unrecognized."

Gami et al prospectively studied 588 volunteers, some of whom were volunteers from the community and others who had specifically been referred to the Mayo Clinic Sleep Disorders Center. All study participants underwent diagnostic polysomnography and provided a family medical history. The authors report that a total of 316 of those for whom complete information was obtained had OSA, while 202 did not. A family history of CAD was reported in roughly two thirds of all OSA and non-OSA subjects; however, a family history of premature death due to CAD was almost twice as high in OSA patients than in non-OSA patients.

In multiple logistic regression analysis, OSA was independently and significantly associated with a family history of premature CAD death, with an adjusted odds ratio of 2.13 (95% CI 1.04-4.66; p=0.046)

"These findings suggest that individuals with OSA, regardless of whether they are healthy or have CAD risk factors, have an increased risk of CAD that is partly due to presently unknown familiar factors acting independently of traditional CAD risk factors," Gami et al write.

Gami added to heartwire that he and his colleagues have a number of studies currently in progress or in development building on the findings of this research, examining potential mechanisms of cardiovascular disease progression and outcomes in OSA patients. But even the data from this current study should be of use to clinicians, he said.

"Together, with the entirety of the evidence, these data should encourage physicians to have a higher suspicion for CAD and to use aggressive prevention interventions in patients with OSA."

-SW