Middle-aged adults with high blood pressure, type 2 diabetes, heart disease or stroke could be at high risk for cancer and early death when sleeping less than six hours per day, according to new research published in the Journal of the American Heart Association.

Researchers analysed data of more than 1,600 adults (20 to 74 years old, more than half women) from the Penn State Adult Cohort who were categorised into two groups as having stage 2 high blood pressure or type 2 diabetes and having heart disease or stroke. Participants were studied in the sleep laboratory (1991-1998) for one night and then researchers tracked their cause of death up to the end of 2016.

They found that of the 512 people who passed away, one-third died of heart disease or stroke and one-fourth died due to cancer.

People who had high blood pressure or diabetes and slept less than six hours had twice the increased risk of dying from heart disease or stroke and those who had heart disease or stroke and slept less than six hours had three times the increased risk of dying from cancer.

The increased risk of early death for people with high blood pressure or diabetes was negligible if they slept for more than six hours.

Normal sleep can reduce risk of early death

"Our study suggests that achieving normal sleep may be protective for some people with these health conditions and risks," said lead study author Julio Fernandez-Mendoza, associate professor at Pennsylvania State College of Medicine and sleep psychologist at the Sleep Research & Treatment Center of the Penn State Health Milton S. Hershey Medical Center in Hershey, Pennsylvania. "However, further research is needed to examine whether improving and increasing sleep through medical or behavioral therapies can reduce risk of early death."

"Short sleep duration should be included as a useful risk factor to predict the long-term outcomes of people with these health conditions and as a target of primary and specialized clinical practices. Better identification of people with specific sleep issues would potentially lead to improved prevention, more complete treatment approaches, better long-term outcomes and less healthcare usage."

Sleep duration in this study was based on observing one night's sleep, which may be affected by the first-night effect where participants sleep significantly worse the first night in a lab compared to other consecutive nights, which is the type of sleep study routinely used in clinical practices.