We have previously shown that in community dwelling elderly, those with more severe sleep apnea, defined as an AHI > 30, had significantly shorter survival (7.9 years) compared to those with AHI < 15 (9.4 years). Multiple regression analysis that included age, gender, BMI, and history of pulmonary or cardiovascular disease, however, resulted in only age, pulmonary and cardiovascular disease, but not AHI, being significant predictors of mortality.2
In a review of sleep apnea and cardiovascular disease, Young and Peppard34
noted that this should not be interpreted as a negative finding. They presented a model of sleep apnea and cardiovascular disease that suggested three components: nightly exposure to sleep apnea as a direct cause of cardiovascular disease, nightly exposure to sleep apnea causing hypertension and thus indirectly causing of cardiovascular disease, or sleep apnea modifying the effect of cardiovascular disease on mortality. Young and Peppard34
suggested that the data of Ancoli-Israel et al2
could be explained by their model, ie, one would not expect AHI to be predictive when cardiovascular disease was controlled for, since the AHI would lead to the cardiovascular disease, which would then lead to death. The same theory could be applied to the data in this study. The fact that men with both CSA and CHF had significantly shorter survival, by several years, than men with just CHF, may reflect the sleep apnea modifying effect of cardiovascular disease on mortality or it may reflect the severity of the heart disease; ie, it is possible that sleep apnea is a marker for the severity of the heart disease rather than a causal factor. Somers,,35
in an editorial, also suggested that the pathophysiology of CHF and of sleep apnea may be linked and in fact may potentiate each other. While additional research is needed to more fully understand these relationships, the results of this study confirm previous findings with a larger sample and longer follow-up.