Recent research from the Smidt Heart Institute shows that between 10 p.m. and 6 a.m., women are more likely than men to die from sudden cardiac arrest. The question remains why.

These findings are especially mystifying since the sleep resting state reduces metabolism, heart rate and blood pressure.

The study examined 3,208 daytime cases of sudden cardiac arrest and 918 nighttime cases. Compared with daytime cases, patients who suffered from nighttime cardiac arrest were more likely to be female.

In some conditions, though, the hazards were shown to be more evenly distributed. The prevalence of chronic obstructive lung disease and asthma were found to be significantly higher in sudden cardiac arrest cases at night compared with daytime cases, regardless of gender.

Individuals taking medications that could affect brain function, such as sedatives and drugs prescribed for pain and depression management, were also at higher risk.

Based on these findings, it is recommended that physicians exercise caution when prescribing brain-affecting medications to high-risk patients—especially women.

In the Newsroom: Sudden Cardiac Death Often A Woman's First Sign of Heart Disease