ATS: Sleep Apnea Hits the Heart, Study Confirms

May 21, 2007

SAN FRANCISCO -- Sleep apnea may increase the risk of heart disease and mortality risk 40%, researchers said here.

SAN FRANCISCO, May 21 -- Sleep apnea may increase the risk of heart disease and mortality risk 40%, researchers said here.

That's the equivalent of having a previous heart attack, said Neomi Shah, M.D., of Yale University, and colleagues at the American Thoracic Society meeting.

"The magnitude of this risk is clinically important," Dr. Shah said.

The researchers' results confirm those of previous, typically smaller studies linking sleep apnea and heart disease, and strengthen the association by controlling for traditional cardiovascular risk factors.

The observational cohort study included 1,640 patients referred to a single center for sleep apnea evaluation (mean age 60 to 61, 63% to 70% male). They underwent overnight polysomnography to determine if they had sleep apnea, defined as an apnea-hypopnea index score over 15.

At baseline, patients with obstructive sleep apnea had slightly higher cardiovascular risk factors.

The mean age of participants was 60 in the non-apnea group and 61 in the apnea group. Hypertension was more common in the apnea group (65% versus 53%, P

Risk increased with severity of apnea as well (P=0.005 for trend).

Those with an apnea-hypopnea index greater than 30 had about twice the risk of cardiac outcomes or mortality compared with those who had the lowest scores (0 to 4).

This suggests causality, said Safwan Badr, M.D., of Wayne State University in Detroit, commenting on the results.

Sleep apnea may trigger the body's "fight or flight" mechanism, decreasing the amount of blood pumped to the heart and possibly starving it of oxygen, Dr. Shah said, describing the possible mechanism involved.

"There's a whole literature emerging on intermittent hypoxia," Dr. Badr said.

However, it remains to be proven that treating the apnea would reduce heart disease risk, Dr. Badr said.

Since the findings of the current study add to a mountain of evidence on detrimental effects of sleep apnea, Dr. Badr said he leans toward treating even moderate cases.

In another study presented here, sleep apnea more than doubled the risk of developing diabetes.

Nader Botros, M.D., of Yale University, and colleagues evaluated more than 500 patients referred to a single center for sleep apnea. After following them for up to six years, sleep apnea increased the adjusted risk of incident diabetes 2.70-fold. More severe apnea was associated with increasing risk of diabetes (P=0.005).