Women are more likely than men to suffer sudden death due to cardiac arrest during night-time hours, a new study suggests.
"Dying suddenly during night-time hours is a perplexing and devastating phenomenon. We were surprised to discover that being female is an independent predictor of these events," said researcher Sumeet Chugh from the Cedars-Sinai Medical Center in the US.
Medical experts are mystified, the researcher said, because during these late hours, most patients are in a resting state, with reduced metabolism, heart rate and blood pressure.
Sudden cardiac arrest - also called sudden cardiac death - is an electrical disturbance of the heart rhythm that causes the heart to stop beating, the researcher said.
For the study, the team of investigators looked at the records of 4,126 patients, with 3,208 daytime cases of sudden cardiac arrest and 918 night-time cases.
Compared with daytime cases, patients who suffered from night-time cardiac arrest were more likely to be female.
The team also found that the prevalence of lung disease was significantly higher in those who had a cardiac arrest at night compared with those who had cardiac arrest during the daytime.
"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," said Chugh.
"Brain-affecting medications, some of which have the potential to suppress breathing, were also found to have a significantly greater usage in night-time compared to daytime cardiac arrest," Chugh added.